Merge commit '6b095f3c8521ca7215e6ff5dcbada52b197ef7d0' as 'tk8.6'

1 files changed, 4073 insertions, 0 deletions

diff --git a/tk8.6/generic/tkImgPhoto.c b/tk8.6/generic/tkImgPhoto.c
new file mode 100644
index 0000000..3e03f3d
--- /dev/null
+++ b/tk8.6/generic/tkImgPhoto.c
@@ -0,0 +1,4073 @@
+/*
+ * tkImgPhoto.c --
+ *
+ *	Implements images of type "photo" for Tk. Photo images are stored in
+ *	full color (32 bits per pixel including alpha channel) and displayed
+ *	using dithering if necessary.
+ *
+ * Copyright (c) 1994 The Australian National University.
+ * Copyright (c) 1994-1997 Sun Microsystems, Inc.
+ * Copyright (c) 2002-2003 Donal K. Fellows
+ * Copyright (c) 2003 ActiveState Corporation.
+ *
+ * See the file "license.terms" for information on usage and redistribution of
+ * this file, and for a DISCLAIMER OF ALL WARRANTIES.
+ *
+ * Author: Paul Mackerras (paulus@cs.anu.edu.au),
+ *	   Department of Computer Science,
+ *	   Australian National University.
+ */
+
+#include "tkImgPhoto.h"
+
+/*
+ * The following data structure is used to return information from
+ * ParseSubcommandOptions:
+ */
+
+struct SubcommandOptions {
+    int options;		/* Individual bits indicate which options were
+				 * specified - see below. */
+    Tcl_Obj *name;		/* Name specified without an option. */
+    int fromX, fromY;		/* Values specified for -from option. */
+    int fromX2, fromY2;		/* Second coordinate pair for -from option. */
+    int toX, toY;		/* Values specified for -to option. */
+    int toX2, toY2;		/* Second coordinate pair for -to option. */
+    int zoomX, zoomY;		/* Values specified for -zoom option. */
+    int subsampleX, subsampleY;	/* Values specified for -subsample option. */
+    Tcl_Obj *format;		/* Value specified for -format option. */
+    XColor *background;		/* Value specified for -background option. */
+    int compositingRule;	/* Value specified for -compositingrule
+				 * option. */
+};
+
+/*
+ * Bit definitions for use with ParseSubcommandOptions: each bit is set in the
+ * allowedOptions parameter on a call to ParseSubcommandOptions if that option
+ * is allowed for the current photo image subcommand. On return, the bit is
+ * set in the options field of the SubcommandOptions structure if that option
+ * was specified.
+ *
+ * OPT_BACKGROUND:		Set if -format option allowed/specified.
+ * OPT_COMPOSITE:		Set if -compositingrule option allowed/spec'd.
+ * OPT_FORMAT:			Set if -format option allowed/specified.
+ * OPT_FROM:			Set if -from option allowed/specified.
+ * OPT_GRAYSCALE:		Set if -grayscale option allowed/specified.
+ * OPT_SHRINK:			Set if -shrink option allowed/specified.
+ * OPT_SUBSAMPLE:		Set if -subsample option allowed/spec'd.
+ * OPT_TO:			Set if -to option allowed/specified.
+ * OPT_ZOOM:			Set if -zoom option allowed/specified.
+ */
+
+#define OPT_BACKGROUND	1
+#define OPT_COMPOSITE	2
+#define OPT_FORMAT	4
+#define OPT_FROM	8
+#define OPT_GRAYSCALE	0x10
+#define OPT_SHRINK	0x20
+#define OPT_SUBSAMPLE	0x40
+#define OPT_TO		0x80
+#define OPT_ZOOM	0x100
+
+/*
+ * List of option names. The order here must match the order of declarations
+ * of the OPT_* constants above.
+ */
+
+static const char *const optionNames[] = {
+    "-background",
+    "-compositingrule",
+    "-format",
+    "-from",
+    "-grayscale",
+    "-shrink",
+    "-subsample",
+    "-to",
+    "-zoom",
+    NULL
+};
+
+/*
+ * Message to generate when an attempt to resize an image fails due to memory
+ * problems.
+ */
+
+#define TK_PHOTO_ALLOC_FAILURE_MESSAGE \
+	"not enough free memory for image buffer"
+
+/*
+ * Functions used in the type record for photo images.
+ */
+
+static int		ImgPhotoCreate(Tcl_Interp *interp, const char *name,
+			    int objc, Tcl_Obj *const objv[],
+			    const Tk_ImageType *typePtr, Tk_ImageMaster master,
+			    ClientData *clientDataPtr);
+static void		ImgPhotoDelete(ClientData clientData);
+static int		ImgPhotoPostscript(ClientData clientData,
+			    Tcl_Interp *interp, Tk_Window tkwin,
+			    Tk_PostscriptInfo psInfo, int x, int y, int width,
+			    int height, int prepass);
+
+/*
+ * The type record itself for photo images:
+ */
+
+Tk_ImageType tkPhotoImageType = {
+    "photo",			/* name */
+    ImgPhotoCreate,		/* createProc */
+    TkImgPhotoGet,		/* getProc */
+    TkImgPhotoDisplay,		/* displayProc */
+    TkImgPhotoFree,		/* freeProc */
+    ImgPhotoDelete,		/* deleteProc */
+    ImgPhotoPostscript,		/* postscriptProc */
+    NULL,			/* nextPtr */
+    NULL
+};
+
+typedef struct ThreadSpecificData {
+    Tk_PhotoImageFormat *formatList;
+				/* Pointer to the first in the list of known
+				 * photo image formats.*/
+    Tk_PhotoImageFormat *oldFormatList;
+				/* Pointer to the first in the list of known
+				 * photo image formats.*/
+    int initialized;		/* Set to 1 if we've initialized the
+				 * structure. */
+} ThreadSpecificData;
+static Tcl_ThreadDataKey dataKey;
+
+/*
+ * Default configuration
+ */
+
+#define DEF_PHOTO_GAMMA		"1"
+#define DEF_PHOTO_HEIGHT	"0"
+#define DEF_PHOTO_PALETTE	""
+#define DEF_PHOTO_WIDTH		"0"
+
+/*
+ * Information used for parsing configuration specifications:
+ */
+
+static const Tk_ConfigSpec configSpecs[] = {
+    {TK_CONFIG_STRING, "-file", NULL, NULL,
+	 NULL, Tk_Offset(PhotoMaster, fileString), TK_CONFIG_NULL_OK, NULL},
+    {TK_CONFIG_DOUBLE, "-gamma", NULL, NULL,
+	 DEF_PHOTO_GAMMA, Tk_Offset(PhotoMaster, gamma), 0, NULL},
+    {TK_CONFIG_INT, "-height", NULL, NULL,
+	 DEF_PHOTO_HEIGHT, Tk_Offset(PhotoMaster, userHeight), 0, NULL},
+    {TK_CONFIG_UID, "-palette", NULL, NULL,
+	 DEF_PHOTO_PALETTE, Tk_Offset(PhotoMaster, palette), 0, NULL},
+    {TK_CONFIG_INT, "-width", NULL, NULL,
+	 DEF_PHOTO_WIDTH, Tk_Offset(PhotoMaster, userWidth), 0, NULL},
+    {TK_CONFIG_END, NULL, NULL, NULL, NULL, 0, 0, NULL}
+};
+
+/*
+ * Forward declarations
+ */
+
+static void		PhotoFormatThreadExitProc(ClientData clientData);
+static int		ImgPhotoCmd(ClientData clientData, Tcl_Interp *interp,
+			    int objc, Tcl_Obj *const objv[]);
+static int		ParseSubcommandOptions(
+			    struct SubcommandOptions *optPtr,
+			    Tcl_Interp *interp, int allowedOptions,
+			    int *indexPtr, int objc, Tcl_Obj *const objv[]);
+static void		ImgPhotoCmdDeletedProc(ClientData clientData);
+static int		ImgPhotoConfigureMaster(Tcl_Interp *interp,
+			    PhotoMaster *masterPtr, int objc,
+			    Tcl_Obj *const objv[], int flags);
+static int		ToggleComplexAlphaIfNeeded(PhotoMaster *mPtr);
+static int		ImgPhotoSetSize(PhotoMaster *masterPtr, int width,
+			    int height);
+static int		ImgStringWrite(Tcl_Interp *interp,
+			    Tcl_Obj *formatString,
+			    Tk_PhotoImageBlock *blockPtr);
+static char *		ImgGetPhoto(PhotoMaster *masterPtr,
+			    Tk_PhotoImageBlock *blockPtr,
+			    struct SubcommandOptions *optPtr);
+static int		MatchFileFormat(Tcl_Interp *interp, Tcl_Channel chan,
+			    const char *fileName, Tcl_Obj *formatString,
+			    Tk_PhotoImageFormat **imageFormatPtr,
+			    int *widthPtr, int *heightPtr, int *oldformat);
+static int		MatchStringFormat(Tcl_Interp *interp, Tcl_Obj *data,
+			    Tcl_Obj *formatString,
+			    Tk_PhotoImageFormat **imageFormatPtr,
+			    int *widthPtr, int *heightPtr, int *oldformat);
+static const char *	GetExtension(const char *path);
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * PhotoFormatThreadExitProc --
+ *
+ *	Clean up the registered list of photo formats.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The thread's linked lists of photo image formats is deleted.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+PhotoFormatThreadExitProc(
+    ClientData clientData)	/* not used */
+{
+    Tk_PhotoImageFormat *freePtr;
+    ThreadSpecificData *tsdPtr =
+	    Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));
+
+    while (tsdPtr->oldFormatList != NULL) {
+	freePtr = tsdPtr->oldFormatList;
+	tsdPtr->oldFormatList = tsdPtr->oldFormatList->nextPtr;
+	ckfree(freePtr);
+    }
+    while (tsdPtr->formatList != NULL) {
+	freePtr = tsdPtr->formatList;
+	tsdPtr->formatList = tsdPtr->formatList->nextPtr;
+	ckfree((char *)freePtr->name);
+	ckfree(freePtr);
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_CreateOldPhotoImageFormat, Tk_CreatePhotoImageFormat --
+ *
+ *	This function is invoked by an image file handler to register a new
+ *	photo image format and the functions that handle the new format. The
+ *	function is typically invoked during Tcl_AppInit.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The new image file format is entered into a table used in the photo
+ *	image "read" and "write" subcommands.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+Tk_CreateOldPhotoImageFormat(
+    const Tk_PhotoImageFormat *formatPtr)
+				/* Structure describing the format. All of the
+				 * fields except "nextPtr" must be filled in
+				 * by caller. */
+{
+    Tk_PhotoImageFormat *copyPtr;
+    ThreadSpecificData *tsdPtr =
+	    Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));
+
+    if (!tsdPtr->initialized) {
+	tsdPtr->initialized = 1;
+	Tcl_CreateThreadExitHandler(PhotoFormatThreadExitProc, NULL);
+    }
+    copyPtr = ckalloc(sizeof(Tk_PhotoImageFormat));
+    *copyPtr = *formatPtr;
+    copyPtr->nextPtr = tsdPtr->oldFormatList;
+    tsdPtr->oldFormatList = copyPtr;
+}
+
+void
+Tk_CreatePhotoImageFormat(
+    const Tk_PhotoImageFormat *formatPtr)
+				/* Structure describing the format. All of the
+				 * fields except "nextPtr" must be filled in
+				 * by caller. */
+{
+    Tk_PhotoImageFormat *copyPtr;
+    ThreadSpecificData *tsdPtr =
+	    Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));
+
+    if (!tsdPtr->initialized) {
+	tsdPtr->initialized = 1;
+	Tcl_CreateThreadExitHandler(PhotoFormatThreadExitProc, NULL);
+    }
+    copyPtr = ckalloc(sizeof(Tk_PhotoImageFormat));
+    *copyPtr = *formatPtr;
+    if (isupper((unsigned char) *formatPtr->name)) {
+	copyPtr->nextPtr = tsdPtr->oldFormatList;
+	tsdPtr->oldFormatList = copyPtr;
+    } else {
+	/* for compatibility with aMSN: make a copy of formatPtr->name */
+	char *name = ckalloc(strlen(formatPtr->name) + 1);
+	strcpy(name, formatPtr->name);
+	copyPtr->name = name;
+	copyPtr->nextPtr = tsdPtr->formatList;
+	tsdPtr->formatList = copyPtr;
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgPhotoCreate --
+ *
+ *	This function is called by the Tk image code to create a new photo
+ *	image.
+ *
+ * Results:
+ *	A standard Tcl result.
+ *
+ * Side effects:
+ *	The data structure for a new photo image is allocated and initialized.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ImgPhotoCreate(
+    Tcl_Interp *interp,		/* Interpreter for application containing
+				 * image. */
+    const char *name,		/* Name to use for image. */
+    int objc,			/* Number of arguments. */
+    Tcl_Obj *const objv[],	/* Argument objects for options (doesn't
+				 * include image name or type). */
+    const Tk_ImageType *typePtr,/* Pointer to our type record (not used). */
+    Tk_ImageMaster master,	/* Token for image, to be used by us in later
+				 * callbacks. */
+    ClientData *clientDataPtr)	/* Store manager's token for image here; it
+				 * will be returned in later callbacks. */
+{
+    PhotoMaster *masterPtr;
+
+    /*
+     * Allocate and initialize the photo image master record.
+     */
+
+    masterPtr = ckalloc(sizeof(PhotoMaster));
+    memset(masterPtr, 0, sizeof(PhotoMaster));
+    masterPtr->tkMaster = master;
+    masterPtr->interp = interp;
+    masterPtr->imageCmd = Tcl_CreateObjCommand(interp, name, ImgPhotoCmd,
+	    masterPtr, ImgPhotoCmdDeletedProc);
+    masterPtr->palette = NULL;
+    masterPtr->pix32 = NULL;
+    masterPtr->instancePtr = NULL;
+    masterPtr->validRegion = TkCreateRegion();
+
+    /*
+     * Process configuration options given in the image create command.
+     */
+
+    if (ImgPhotoConfigureMaster(interp, masterPtr, objc, objv, 0) != TCL_OK) {
+	ImgPhotoDelete(masterPtr);
+	return TCL_ERROR;
+    }
+
+    *clientDataPtr = masterPtr;
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgPhotoCmd --
+ *
+ *	This function is invoked to process the Tcl command that corresponds
+ *	to a photo image. See the user documentation for details on what it
+ *	does.
+ *
+ * Results:
+ *	A standard Tcl result.
+ *
+ * Side effects:
+ *	See the user documentation.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ImgPhotoCmd(
+    ClientData clientData,	/* Information about photo master. */
+    Tcl_Interp *interp,		/* Current interpreter. */
+    int objc,			/* Number of arguments. */
+    Tcl_Obj *const objv[])	/* Argument objects. */
+{
+    static const char *const photoOptions[] = {
+	"blank", "cget", "configure", "copy", "data", "get", "put",
+	"read", "redither", "transparency", "write", NULL
+    };
+    enum PhotoOptions {
+	PHOTO_BLANK, PHOTO_CGET, PHOTO_CONFIGURE, PHOTO_COPY, PHOTO_DATA,
+	PHOTO_GET, PHOTO_PUT, PHOTO_READ, PHOTO_REDITHER, PHOTO_TRANS,
+	PHOTO_WRITE
+    };
+
+    PhotoMaster *masterPtr = clientData;
+    int result, index, x, y, width, height, dataWidth, dataHeight, listObjc;
+    struct SubcommandOptions options;
+    Tcl_Obj **listObjv, **srcObjv;
+    unsigned char *pixelPtr;
+    Tk_PhotoImageBlock block;
+    Tk_Window tkwin;
+    Tk_PhotoImageFormat *imageFormat;
+    int imageWidth, imageHeight, matched, length, oldformat = 0;
+    Tcl_Channel chan;
+    Tk_PhotoHandle srcHandle;
+    ThreadSpecificData *tsdPtr =
+	    Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));
+
+    if (objc < 2) {
+	Tcl_WrongNumArgs(interp, 1, objv, "option ?arg ...?");
+	return TCL_ERROR;
+    }
+
+    if (Tcl_GetIndexFromObj(interp, objv[1], photoOptions, "option", 0,
+	    &index) != TCL_OK) {
+	return TCL_ERROR;
+    }
+
+    switch ((enum PhotoOptions) index) {
+    case PHOTO_BLANK:
+	/*
+	 * photo blank command - just call Tk_PhotoBlank.
+	 */
+
+	if (objc == 2) {
+	    Tk_PhotoBlank(masterPtr);
+	    return TCL_OK;
+	} else {
+	    Tcl_WrongNumArgs(interp, 2, objv, NULL);
+	    return TCL_ERROR;
+	}
+
+    case PHOTO_CGET: {
+	const char *arg;
+
+	if (objc != 3) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "option");
+	    return TCL_ERROR;
+	}
+	arg = Tcl_GetStringFromObj(objv[2], &length);
+	if (strncmp(arg,"-data", (unsigned) length) == 0) {
+	    if (masterPtr->dataString) {
+		Tcl_SetObjResult(interp, masterPtr->dataString);
+	    }
+	} else if (strncmp(arg,"-format", (unsigned) length) == 0) {
+	    if (masterPtr->format) {
+		Tcl_SetObjResult(interp, masterPtr->format);
+	    }
+	} else {
+	    Tk_ConfigureValue(interp, Tk_MainWindow(interp), configSpecs,
+		    (char *) masterPtr, Tcl_GetString(objv[2]), 0);
+	}
+	return TCL_OK;
+    }
+
+    case PHOTO_CONFIGURE:
+	/*
+	 * photo configure command - handle this in the standard way.
+	 */
+
+	if (objc == 2) {
+	    Tcl_Obj *obj, *subobj;
+
+	    result = Tk_ConfigureInfo(interp, Tk_MainWindow(interp),
+		    configSpecs, (char *) masterPtr, NULL, 0);
+	    if (result != TCL_OK) {
+		return result;
+	    }
+	    obj = Tcl_NewObj();
+	    subobj = Tcl_NewStringObj("-data {} {} {}", 14);
+	    if (masterPtr->dataString) {
+		Tcl_ListObjAppendElement(NULL, subobj, masterPtr->dataString);
+	    } else {
+		Tcl_AppendStringsToObj(subobj, " {}", NULL);
+	    }
+	    Tcl_ListObjAppendElement(interp, obj, subobj);
+	    subobj = Tcl_NewStringObj("-format {} {} {}", 16);
+	    if (masterPtr->format) {
+		Tcl_ListObjAppendElement(NULL, subobj, masterPtr->format);
+	    } else {
+		Tcl_AppendStringsToObj(subobj, " {}", NULL);
+	    }
+	    Tcl_ListObjAppendElement(interp, obj, subobj);
+	    Tcl_ListObjAppendList(interp, obj, Tcl_GetObjResult(interp));
+	    Tcl_SetObjResult(interp, obj);
+	    return TCL_OK;
+
+	} else if (objc == 3) {
+	    const char *arg = Tcl_GetStringFromObj(objv[2], &length);
+
+	    if (length > 1 && !strncmp(arg, "-data", (unsigned) length)) {
+		Tcl_AppendResult(interp, "-data {} {} {}", NULL);
+		if (masterPtr->dataString) {
+		    /*
+		     * TODO: Modifying result is bad!
+		     */
+
+		    Tcl_ListObjAppendElement(NULL, Tcl_GetObjResult(interp),
+			    masterPtr->dataString);
+		} else {
+		    Tcl_AppendResult(interp, " {}", NULL);
+		}
+		return TCL_OK;
+	    } else if (length > 1 &&
+		    !strncmp(arg, "-format", (unsigned) length)) {
+		Tcl_AppendResult(interp, "-format {} {} {}", NULL);
+		if (masterPtr->format) {
+		    /*
+		     * TODO: Modifying result is bad!
+		     */
+
+		    Tcl_ListObjAppendElement(NULL, Tcl_GetObjResult(interp),
+			    masterPtr->format);
+		} else {
+		    Tcl_AppendResult(interp, " {}", NULL);
+		}
+		return TCL_OK;
+	    } else {
+		return Tk_ConfigureInfo(interp, Tk_MainWindow(interp),
+			configSpecs, (char *) masterPtr, arg, 0);
+	    }
+	} else {
+	    return ImgPhotoConfigureMaster(interp, masterPtr, objc-2, objv+2,
+		    TK_CONFIG_ARGV_ONLY);
+	}
+
+    case PHOTO_COPY:
+	/*
+	 * photo copy command - first parse options.
+	 */
+
+	index = 2;
+	memset(&options, 0, sizeof(options));
+	options.zoomX = options.zoomY = 1;
+	options.subsampleX = options.subsampleY = 1;
+	options.name = NULL;
+	options.compositingRule = TK_PHOTO_COMPOSITE_OVERLAY;
+	if (ParseSubcommandOptions(&options, interp,
+		OPT_FROM | OPT_TO | OPT_ZOOM | OPT_SUBSAMPLE | OPT_SHRINK |
+		OPT_COMPOSITE, &index, objc, objv) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if (options.name == NULL || index < objc) {
+	    Tcl_WrongNumArgs(interp, 2, objv,
+		    "source-image ?-compositingrule rule? ?-from x1 y1 x2 y2? ?-to x1 y1 x2 y2? ?-zoom x y? ?-subsample x y?");
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Look for the source image and get a pointer to its image data.
+	 * Check the values given for the -from option.
+	 */
+
+	srcHandle = Tk_FindPhoto(interp, Tcl_GetString(options.name));
+	if (srcHandle == NULL) {
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "image \"%s\" doesn't exist or is not a photo image",
+		    Tcl_GetString(options.name)));
+	    Tcl_SetErrorCode(interp, "TK", "LOOKUP", "PHOTO",
+		    Tcl_GetString(options.name), NULL);
+	    return TCL_ERROR;
+	}
+	Tk_PhotoGetImage(srcHandle, &block);
+	if ((options.fromX2 > block.width) || (options.fromY2 > block.height)
+		|| (options.fromX2 > block.width)
+		|| (options.fromY2 > block.height)) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "coordinates for -from option extend outside source image",
+		    -1));
+	    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "BAD_FROM", NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Hack to pass through the message that the place we're coming from
+	 * has a simple alpha channel.
+	 */
+
+	if (!(((PhotoMaster *) srcHandle)->flags & COMPLEX_ALPHA)) {
+	    options.compositingRule |= SOURCE_IS_SIMPLE_ALPHA_PHOTO;
+	}
+
+	/*
+	 * Fill in default values for unspecified parameters.
+	 */
+
+	if (!(options.options & OPT_FROM) || (options.fromX2 < 0)) {
+	    options.fromX2 = block.width;
+	    options.fromY2 = block.height;
+	}
+	if (!(options.options & OPT_TO) || (options.toX2 < 0)) {
+	    width = options.fromX2 - options.fromX;
+	    if (options.subsampleX > 0) {
+		width = (width + options.subsampleX - 1) / options.subsampleX;
+	    } else if (options.subsampleX == 0) {
+		width = 0;
+	    } else {
+		width = (width - options.subsampleX - 1) / -options.subsampleX;
+	    }
+	    options.toX2 = options.toX + width * options.zoomX;
+
+	    height = options.fromY2 - options.fromY;
+	    if (options.subsampleY > 0) {
+		height = (height + options.subsampleY - 1)
+			/ options.subsampleY;
+	    } else if (options.subsampleY == 0) {
+		height = 0;
+	    } else {
+		height = (height - options.subsampleY - 1)
+			/ -options.subsampleY;
+	    }
+	    options.toY2 = options.toY + height * options.zoomY;
+	}
+
+	/*
+	 * Set the destination image size if the -shrink option was specified.
+	 */
+
+	if (options.options & OPT_SHRINK) {
+	    if (ImgPhotoSetSize(masterPtr, options.toX2,
+		    options.toY2) != TCL_OK) {
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+		Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+		return TCL_ERROR;
+	    }
+	}
+
+	/*
+	 * Copy the image data over using Tk_PhotoPutZoomedBlock.
+	 */
+
+	block.pixelPtr += options.fromX * block.pixelSize
+		+ options.fromY * block.pitch;
+	block.width = options.fromX2 - options.fromX;
+	block.height = options.fromY2 - options.fromY;
+	return Tk_PhotoPutZoomedBlock(interp, (Tk_PhotoHandle) masterPtr,
+		&block, options.toX, options.toY, options.toX2 - options.toX,
+		options.toY2 - options.toY, options.zoomX, options.zoomY,
+		options.subsampleX, options.subsampleY,
+		options.compositingRule);
+
+    case PHOTO_DATA: {
+	char *data;
+
+	/*
+	 * photo data command - first parse and check any options given.
+	 */
+
+	Tk_ImageStringWriteProc *stringWriteProc = NULL;
+
+	index = 2;
+	memset(&options, 0, sizeof(options));
+	options.name = NULL;
+	options.format = NULL;
+	options.fromX = 0;
+	options.fromY = 0;
+	if (ParseSubcommandOptions(&options, interp,
+		OPT_FORMAT | OPT_FROM | OPT_GRAYSCALE | OPT_BACKGROUND,
+		&index, objc, objv) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if ((options.name != NULL) || (index < objc)) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "?-option value ...?");
+	    return TCL_ERROR;
+	}
+	if ((options.fromX > masterPtr->width)
+		|| (options.fromY > masterPtr->height)
+		|| (options.fromX2 > masterPtr->width)
+		|| (options.fromY2 > masterPtr->height)) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "coordinates for -from option extend outside image", -1));
+	    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "BAD_FROM", NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Fill in default values for unspecified parameters.
+	 */
+
+	if (!(options.options & OPT_FROM) || (options.fromX2 < 0)) {
+	    options.fromX2 = masterPtr->width;
+	    options.fromY2 = masterPtr->height;
+	}
+
+	/*
+	 * Search for an appropriate image string format handler.
+	 */
+
+	if (options.options & OPT_FORMAT) {
+	    matched = 0;
+	    for (imageFormat = tsdPtr->formatList; imageFormat != NULL;
+	 	imageFormat = imageFormat->nextPtr) {
+		if ((strncasecmp(Tcl_GetString(options.format),
+			imageFormat->name, strlen(imageFormat->name)) == 0)) {
+		    matched = 1;
+		    if (imageFormat->stringWriteProc != NULL) {
+			stringWriteProc = imageFormat->stringWriteProc;
+			break;
+		    }
+		}
+	    }
+	    if (stringWriteProc == NULL) {
+		oldformat = 1;
+		for (imageFormat = tsdPtr->oldFormatList; imageFormat != NULL;
+			imageFormat = imageFormat->nextPtr) {
+		    if ((strncasecmp(Tcl_GetString(options.format),
+			    imageFormat->name,
+			    strlen(imageFormat->name)) == 0)) {
+			matched = 1;
+			if (imageFormat->stringWriteProc != NULL) {
+			    stringWriteProc = imageFormat->stringWriteProc;
+			    break;
+			}
+		    }
+		}
+	    }
+	    if (stringWriteProc == NULL) {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"image string format \"%s\" is %s",
+			Tcl_GetString(options.format),
+			(matched ? "not supported" : "unknown")));
+		Tcl_SetErrorCode(interp, "TK", "LOOKUP", "PHOTO_FORMAT",
+			Tcl_GetString(options.format), NULL);
+		return TCL_ERROR;
+	    }
+	} else {
+	    stringWriteProc = ImgStringWrite;
+	}
+
+	/*
+	 * Call the handler's string write function to write out the image.
+	 */
+
+	data = ImgGetPhoto(masterPtr, &block, &options);
+
+	if (oldformat) {
+	    Tcl_DString buffer;
+	    typedef int (*OldStringWriteProc)(Tcl_Interp *interp,
+		    Tcl_DString *dataPtr, const char *formatString,
+		    Tk_PhotoImageBlock *blockPtr);
+
+	    Tcl_DStringInit(&buffer);
+	    result = ((OldStringWriteProc) stringWriteProc)(interp, &buffer,
+		    Tcl_GetString(options.format), &block);
+	    if (result == TCL_OK) {
+		Tcl_DStringResult(interp, &buffer);
+	    } else {
+		Tcl_DStringFree(&buffer);
+	    }
+	} else {
+	    typedef int (*NewStringWriteProc)(Tcl_Interp *interp,
+		    Tcl_Obj *formatString, Tk_PhotoImageBlock *blockPtr,
+		    void *dummy);
+
+	    result = ((NewStringWriteProc) stringWriteProc)(interp,
+		    options.format, &block, NULL);
+	}
+	if (options.background) {
+	    Tk_FreeColor(options.background);
+	}
+	if (data) {
+	    ckfree(data);
+	}
+	return result;
+    }
+
+    case PHOTO_GET: {
+	/*
+	 * photo get command - first parse and check parameters.
+	 */
+
+	Tcl_Obj *channels[3];
+
+	if (objc != 4) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "x y");
+	    return TCL_ERROR;
+	}
+	if ((Tcl_GetIntFromObj(interp, objv[2], &x) != TCL_OK)
+		|| (Tcl_GetIntFromObj(interp, objv[3], &y) != TCL_OK)) {
+	    return TCL_ERROR;
+	}
+	if ((x < 0) || (x >= masterPtr->width)
+		|| (y < 0) || (y >= masterPtr->height)) {
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "%s get: coordinates out of range",
+		    Tcl_GetString(objv[0])));
+	    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "COORDINATES",
+		    NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Extract the value of the desired pixel and format it as a string.
+	 */
+
+	pixelPtr = masterPtr->pix32 + (y * masterPtr->width + x) * 4;
+	channels[0] = Tcl_NewIntObj(pixelPtr[0]);
+	channels[1] = Tcl_NewIntObj(pixelPtr[1]);
+	channels[2] = Tcl_NewIntObj(pixelPtr[2]);
+	Tcl_SetObjResult(interp, Tcl_NewListObj(3, channels));
+	return TCL_OK;
+    }
+
+    case PHOTO_PUT:
+	/*
+	 * photo put command - first parse the options and colors specified.
+	 */
+
+	index = 2;
+	memset(&options, 0, sizeof(options));
+	options.name = NULL;
+	if (ParseSubcommandOptions(&options, interp, OPT_TO|OPT_FORMAT,
+		&index, objc, objv) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if ((options.name == NULL) || (index < objc)) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "data ?-option value ...?");
+	    return TCL_ERROR;
+	}
+
+	if (MatchStringFormat(interp, options.name ? objv[2]:NULL,
+		options.format, &imageFormat, &imageWidth,
+		&imageHeight, &oldformat) == TCL_OK) {
+	    Tcl_Obj *format, *data;
+
+	    if (!(options.options & OPT_TO) || (options.toX2 < 0)) {
+		options.toX2 = options.toX + imageWidth;
+		options.toY2 = options.toY + imageHeight;
+	    }
+	    if (imageWidth > options.toX2 - options.toX) {
+		imageWidth = options.toX2 - options.toX;
+	    }
+	    if (imageHeight > options.toY2 - options.toY) {
+		imageHeight = options.toY2 - options.toY;
+	    }
+	    format = options.format;
+	    data = objv[2];
+	    if (oldformat) {
+		if (format) {
+		    format = (Tcl_Obj *) Tcl_GetString(format);
+		}
+		data = (Tcl_Obj *) Tcl_GetString(data);
+	    }
+	    if (imageFormat->stringReadProc(interp, data, format,
+		    (Tk_PhotoHandle) masterPtr, options.toX, options.toY,
+		    imageWidth, imageHeight, 0, 0) != TCL_OK) {
+		return TCL_ERROR;
+	    }
+	    masterPtr->flags |= IMAGE_CHANGED;
+	    return TCL_OK;
+	}
+	if (options.options & OPT_FORMAT) {
+	    return TCL_ERROR;
+	}
+	Tcl_ResetResult(interp);
+	if (Tcl_ListObjGetElements(interp, options.name,
+		&dataHeight, &srcObjv) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	tkwin = Tk_MainWindow(interp);
+	block.pixelPtr = NULL;
+	dataWidth = 0;
+	pixelPtr = NULL;
+	for (y = 0; y < dataHeight; ++y) {
+	    if (Tcl_ListObjGetElements(interp, srcObjv[y],
+		    &listObjc, &listObjv) != TCL_OK) {
+		break;
+	    }
+
+	    if (y == 0) {
+		if (listObjc == 0) {
+		    /*
+		     * Lines must be non-empty...
+		     */
+
+		    break;
+		}
+		dataWidth = listObjc;
+		/*
+ 		 * Memory allocation overflow protection.
+ 		 * May not be able to trigger/ demo / test this.
+ 		 */
+
+		if (dataWidth > (int)((UINT_MAX/3) / dataHeight)) {
+		    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			"photo image dimensions exceed Tcl memory limits", -1));
+		    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			"OVERFLOW", NULL);
+		    break;
+		}
+
+		pixelPtr = ckalloc(dataWidth * dataHeight * 3);
+		block.pixelPtr = pixelPtr;
+	    } else if (listObjc != dataWidth) {
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			"all elements of color list must have the same"
+			" number of elements", -1));
+		Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			"NON_RECTANGULAR", NULL);
+		break;
+	    }
+
+	    for (x = 0; x < dataWidth; ++x) {
+		const char *colorString = Tcl_GetString(listObjv[x]);
+		XColor color;
+		int tmpr, tmpg, tmpb;
+
+		/*
+		 * We do not use Tk_GetColorFromObj() because we absolutely do
+		 * not want to invoke the fallback code.
+		 */
+
+		if (colorString[0] == '#') {
+		    if (isxdigit(UCHAR(colorString[1])) &&
+			    isxdigit(UCHAR(colorString[2])) &&
+			    isxdigit(UCHAR(colorString[3]))) {
+			if (colorString[4] == '\0') {
+			    /* Got #rgb */
+			    sscanf(colorString+1, "%1x%1x%1x",
+				    &tmpr, &tmpg, &tmpb);
+			    *pixelPtr++ = tmpr * 0x11;
+			    *pixelPtr++ = tmpg * 0x11;
+			    *pixelPtr++ = tmpb * 0x11;
+			    continue;
+			} else if (isxdigit(UCHAR(colorString[4])) &&
+				isxdigit(UCHAR(colorString[5])) &&
+				isxdigit(UCHAR(colorString[6])) &&
+				colorString[7] == '\0') {
+			    /* Got #rrggbb */
+			    sscanf(colorString+1, "%2x%2x%2x",
+				    &tmpr, &tmpg, &tmpb);
+			    *pixelPtr++ = tmpr;
+			    *pixelPtr++ = tmpg;
+			    *pixelPtr++ = tmpb;
+			    continue;
+			}
+		    }
+		}
+
+		if (!TkParseColor(Tk_Display(tkwin), Tk_Colormap(tkwin),
+			colorString, &color)) {
+		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			    "can't parse color \"%s\"", colorString));
+		    Tcl_SetErrorCode(interp, "TK", "VALUE", "COLOR", NULL);
+		    break;
+		}
+		*pixelPtr++ = color.red >> 8;
+		*pixelPtr++ = color.green >> 8;
+		*pixelPtr++ = color.blue >> 8;
+	    }
+	    if (x < dataWidth) {
+		break;
+	    }
+	}
+	if (y < dataHeight || dataHeight == 0 || dataWidth == 0) {
+	    if (block.pixelPtr != NULL) {
+		ckfree(block.pixelPtr);
+	    }
+	    if (y < dataHeight) {
+		return TCL_ERROR;
+	    }
+	    return TCL_OK;
+	}
+
+	/*
+	 * Fill in default values for the -to option, then copy the block in
+	 * using Tk_PhotoPutBlock.
+	 */
+
+	if (!(options.options & OPT_TO) || (options.toX2 < 0)) {
+	    options.toX2 = options.toX + dataWidth;
+	    options.toY2 = options.toY + dataHeight;
+	}
+	block.width = dataWidth;
+	block.height = dataHeight;
+	block.pitch = dataWidth * 3;
+	block.pixelSize = 3;
+	block.offset[0] = 0;
+	block.offset[1] = 1;
+	block.offset[2] = 2;
+	block.offset[3] = 0;
+	result = Tk_PhotoPutBlock(interp, masterPtr, &block,
+		options.toX, options.toY, options.toX2 - options.toX,
+		options.toY2 - options.toY,
+		TK_PHOTO_COMPOSITE_SET);
+	ckfree(block.pixelPtr);
+	return result;
+
+    case PHOTO_READ: {
+	Tcl_Obj *format;
+
+	/*
+	 * photo read command - first parse the options specified.
+	 */
+
+	index = 2;
+	memset(&options, 0, sizeof(options));
+	options.name = NULL;
+	options.format = NULL;
+	if (ParseSubcommandOptions(&options, interp,
+		OPT_FORMAT | OPT_FROM | OPT_TO | OPT_SHRINK,
+		&index, objc, objv) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if ((options.name == NULL) || (index < objc)) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "fileName ?-option value ...?");
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Prevent file system access in safe interpreters.
+	 */
+
+	if (Tcl_IsSafe(interp)) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "can't get image from a file in a safe interpreter", -1));
+	    Tcl_SetErrorCode(interp, "TK", "SAFE", "PHOTO_FILE", NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Open the image file and look for a handler for it.
+	 */
+
+	chan = Tcl_OpenFileChannel(interp,
+		Tcl_GetString(options.name), "r", 0);
+	if (chan == NULL) {
+	    return TCL_ERROR;
+	}
+	if (Tcl_SetChannelOption(interp, chan, "-translation", "binary")
+		!= TCL_OK) {
+	    Tcl_Close(NULL, chan);
+	    return TCL_ERROR;
+	}
+	if (Tcl_SetChannelOption(interp, chan, "-encoding", "binary")
+		!= TCL_OK) {
+	    Tcl_Close(NULL, chan);
+	    return TCL_ERROR;
+	}
+
+	if (MatchFileFormat(interp, chan,
+		Tcl_GetString(options.name), options.format, &imageFormat,
+		&imageWidth, &imageHeight, &oldformat) != TCL_OK) {
+	    Tcl_Close(NULL, chan);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Check the values given for the -from option.
+	 */
+
+	if ((options.fromX > imageWidth) || (options.fromY > imageHeight)
+		|| (options.fromX2 > imageWidth)
+		|| (options.fromY2 > imageHeight)) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "coordinates for -from option extend outside source image",
+		    -1));
+	    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "BAD_FROM", NULL);
+	    Tcl_Close(NULL, chan);
+	    return TCL_ERROR;
+	}
+	if (!(options.options & OPT_FROM) || (options.fromX2 < 0)) {
+	    width = imageWidth - options.fromX;
+	    height = imageHeight - options.fromY;
+	} else {
+	    width = options.fromX2 - options.fromX;
+	    height = options.fromY2 - options.fromY;
+	}
+
+	/*
+	 * If the -shrink option was specified, set the size of the image.
+	 */
+
+	if (options.options & OPT_SHRINK) {
+	    if (ImgPhotoSetSize(masterPtr, options.toX + width,
+		    options.toY + height) != TCL_OK) {
+		Tcl_ResetResult(interp);
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+		Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+		return TCL_ERROR;
+	    }
+	}
+
+	/*
+	 * Call the handler's file read function to read the data into the
+	 * image.
+	 */
+
+	format = options.format;
+	if (oldformat && format) {
+	    format = (Tcl_Obj *) Tcl_GetString(format);
+	}
+	result = imageFormat->fileReadProc(interp, chan,
+		Tcl_GetString(options.name),
+		format, (Tk_PhotoHandle) masterPtr, options.toX,
+		options.toY, width, height, options.fromX, options.fromY);
+	if (chan != NULL) {
+	    Tcl_Close(NULL, chan);
+	}
+	return result;
+    }
+
+    case PHOTO_REDITHER:
+	if (objc != 2) {
+	    Tcl_WrongNumArgs(interp, 2, objv, NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Call Dither if any part of the image is not correctly dithered at
+	 * present.
+	 */
+
+	x = masterPtr->ditherX;
+	y = masterPtr->ditherY;
+	if (masterPtr->ditherX != 0) {
+	    Tk_DitherPhoto((Tk_PhotoHandle) masterPtr, x, y,
+		    masterPtr->width - x, 1);
+	}
+	if (masterPtr->ditherY < masterPtr->height) {
+	    x = 0;
+	    Tk_DitherPhoto((Tk_PhotoHandle)masterPtr, 0,
+		    masterPtr->ditherY, masterPtr->width,
+		    masterPtr->height - masterPtr->ditherY);
+	}
+
+	if (y < masterPtr->height) {
+	    /*
+	     * Tell the core image code that part of the image has changed.
+	     */
+
+	    Tk_ImageChanged(masterPtr->tkMaster, x, y,
+		    (masterPtr->width - x), (masterPtr->height - y),
+		    masterPtr->width, masterPtr->height);
+	}
+	return TCL_OK;
+
+    case PHOTO_TRANS: {
+	static const char *const photoTransOptions[] = {
+	    "get", "set", NULL
+	};
+	enum transOptions {
+	    PHOTO_TRANS_GET, PHOTO_TRANS_SET
+	};
+
+	if (objc < 3) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "option ?arg ...?");
+	    return TCL_ERROR;
+	}
+	if (Tcl_GetIndexFromObj(interp, objv[2], photoTransOptions, "option",
+		0, &index) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+
+	switch ((enum transOptions) index) {
+	case PHOTO_TRANS_GET: {
+	    XRectangle testBox;
+	    TkRegion testRegion;
+
+	    if (objc != 5) {
+		Tcl_WrongNumArgs(interp, 3, objv, "x y");
+		return TCL_ERROR;
+	    }
+	    if ((Tcl_GetIntFromObj(interp, objv[3], &x) != TCL_OK)
+		    || (Tcl_GetIntFromObj(interp, objv[4], &y) != TCL_OK)) {
+		return TCL_ERROR;
+	    }
+	    if ((x < 0) || (x >= masterPtr->width)
+		    || (y < 0) || (y >= masterPtr->height)) {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"%s transparency get: coordinates out of range",
+			Tcl_GetString(objv[0])));
+		Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "COORDINATES",
+			NULL);
+		return TCL_ERROR;
+	    }
+
+	    testBox.x = x;
+	    testBox.y = y;
+	    testBox.width = 1;
+	    testBox.height = 1;
+	    /* What a way to do a test! */
+	    testRegion = TkCreateRegion();
+	    TkUnionRectWithRegion(&testBox, testRegion, testRegion);
+	    TkIntersectRegion(testRegion, masterPtr->validRegion, testRegion);
+	    TkClipBox(testRegion, &testBox);
+	    TkDestroyRegion(testRegion);
+
+	    Tcl_SetObjResult(interp, Tcl_NewBooleanObj(
+		    testBox.width==0 && testBox.height==0));
+	    return TCL_OK;
+	}
+
+	case PHOTO_TRANS_SET: {
+	    int transFlag;
+	    XRectangle setBox;
+
+	    if (objc != 6) {
+		Tcl_WrongNumArgs(interp, 3, objv, "x y boolean");
+		return TCL_ERROR;
+	    }
+	    if ((Tcl_GetIntFromObj(interp, objv[3], &x) != TCL_OK)
+		    || (Tcl_GetIntFromObj(interp, objv[4], &y) != TCL_OK)
+		    || (Tcl_GetBooleanFromObj(interp, objv[5],
+		    &transFlag) != TCL_OK)) {
+		return TCL_ERROR;
+	    }
+	    if ((x < 0) || (x >= masterPtr->width)
+		|| (y < 0) || (y >= masterPtr->height)) {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"%s transparency set: coordinates out of range",
+			Tcl_GetString(objv[0])));
+		Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "COORDINATES",
+			NULL);
+		return TCL_ERROR;
+	    }
+
+	    setBox.x = x;
+	    setBox.y = y;
+	    setBox.width = 1;
+	    setBox.height = 1;
+	    pixelPtr = masterPtr->pix32 + (y * masterPtr->width + x) * 4;
+
+	    if (transFlag) {
+		/*
+		 * Make pixel transparent.
+		 */
+
+		TkRegion clearRegion = TkCreateRegion();
+
+		TkUnionRectWithRegion(&setBox, clearRegion, clearRegion);
+		TkSubtractRegion(masterPtr->validRegion, clearRegion,
+			masterPtr->validRegion);
+		TkDestroyRegion(clearRegion);
+
+		/*
+		 * Set the alpha value correctly.
+		 */
+
+		pixelPtr[3] = 0;
+	    } else {
+		/*
+		 * Make pixel opaque.
+		 */
+
+		TkUnionRectWithRegion(&setBox, masterPtr->validRegion,
+			masterPtr->validRegion);
+		pixelPtr[3] = 255;
+	    }
+
+	    /*
+	     * Inform the generic image code that the image
+	     * has (potentially) changed.
+	     */
+
+	    Tk_ImageChanged(masterPtr->tkMaster, x, y, 1, 1,
+		    masterPtr->width, masterPtr->height);
+	    masterPtr->flags &= ~IMAGE_CHANGED;
+	    return TCL_OK;
+	}
+
+	}
+	Tcl_Panic("unexpected fallthrough");
+    }
+
+    case PHOTO_WRITE: {
+	char *data;
+	const char *fmtString;
+	Tcl_Obj *format;
+	int usedExt;
+
+	/*
+	 * Prevent file system access in safe interpreters.
+	 */
+
+	if (Tcl_IsSafe(interp)) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "can't write image to a file in a safe interpreter", -1));
+	    Tcl_SetErrorCode(interp, "TK", "SAFE", "PHOTO_FILE", NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * photo write command - first parse and check any options given.
+	 */
+
+	index = 2;
+	memset(&options, 0, sizeof(options));
+	options.name = NULL;
+	options.format = NULL;
+	if (ParseSubcommandOptions(&options, interp,
+		OPT_FORMAT | OPT_FROM | OPT_GRAYSCALE | OPT_BACKGROUND,
+		&index, objc, objv) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if ((options.name == NULL) || (index < objc)) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "fileName ?-option value ...?");
+	    return TCL_ERROR;
+	}
+	if ((options.fromX > masterPtr->width)
+		|| (options.fromY > masterPtr->height)
+		|| (options.fromX2 > masterPtr->width)
+		|| (options.fromY2 > masterPtr->height)) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "coordinates for -from option extend outside image", -1));
+	    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "BAD_FROM", NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Fill in default values for unspecified parameters. Note that a
+	 * missing -format flag results in us having a guess from the file
+	 * extension. [Bug 2983824]
+	 */
+
+	if (!(options.options & OPT_FROM) || (options.fromX2 < 0)) {
+	    options.fromX2 = masterPtr->width;
+	    options.fromY2 = masterPtr->height;
+	}
+	if (options.format == NULL) {
+	    fmtString = GetExtension(Tcl_GetString(options.name));
+	    usedExt = (fmtString != NULL);
+	} else {
+	    fmtString = Tcl_GetString(options.format);
+	    usedExt = 0;
+	}
+
+	/*
+	 * Search for an appropriate image file format handler, and give an
+	 * error if none is found.
+	 */
+
+	matched = 0;
+    redoFormatLookup:
+	for (imageFormat = tsdPtr->formatList; imageFormat != NULL;
+		imageFormat = imageFormat->nextPtr) {
+	    if ((fmtString == NULL)
+		    || (strncasecmp(fmtString, imageFormat->name,
+			    strlen(imageFormat->name)) == 0)) {
+		matched = 1;
+		if (imageFormat->fileWriteProc != NULL) {
+		    break;
+		}
+	    }
+	}
+	if (imageFormat == NULL) {
+	    oldformat = 1;
+	    for (imageFormat = tsdPtr->oldFormatList; imageFormat != NULL;
+		    imageFormat = imageFormat->nextPtr) {
+		if ((fmtString == NULL)
+			|| (strncasecmp(fmtString, imageFormat->name,
+				strlen(imageFormat->name)) == 0)) {
+		    matched = 1;
+		    if (imageFormat->fileWriteProc != NULL) {
+			break;
+		    }
+		}
+	    }
+	}
+	if (usedExt && !matched) {
+	    /*
+	     * If we didn't find one and we're using file extensions as the
+	     * basis for the guessing, go back and look again without
+	     * prejudice. Supports old broken code.
+	     */
+
+	    usedExt = 0;
+	    fmtString = NULL;
+	    goto redoFormatLookup;
+	}
+	if (imageFormat == NULL) {
+	    if (fmtString == NULL) {
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			"no available image file format has file writing"
+			" capability", -1));
+	    } else if (!matched) {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"image file format \"%s\" is unknown", fmtString));
+	    } else {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"image file format \"%s\" has no file writing capability",
+			fmtString));
+	    }
+	    Tcl_SetErrorCode(interp, "TK", "LOOKUP", "PHOTO_FORMAT",
+		    fmtString, NULL);
+	    return TCL_ERROR;
+	}
+
+	/*
+	 * Call the handler's file write function to write out the image.
+	 */
+
+	data = ImgGetPhoto(masterPtr, &block, &options);
+	format = options.format;
+	if (oldformat && format) {
+	    format = (Tcl_Obj *) Tcl_GetString(options.format);
+	}
+	result = imageFormat->fileWriteProc(interp,
+		Tcl_GetString(options.name), format, &block);
+	if (options.background) {
+	    Tk_FreeColor(options.background);
+	}
+	if (data) {
+	    ckfree(data);
+	}
+	return result;
+    }
+
+    }
+    Tcl_Panic("unexpected fallthrough");
+    return TCL_ERROR; /* NOT REACHED */
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * GetExtension --
+ *
+ *	Return the extension part of a path, or NULL if there is no extension.
+ *	The returned string will be a substring of the argument string, so
+ *	should not be ckfree()d directly. No side effects.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static const char *
+GetExtension(
+    const char *path)
+{
+    char c;
+    const char *extension = NULL;
+
+    for (; (c=*path++) != '\0' ;) {
+	if (c == '.') {
+	    extension = path;
+	}
+    }
+    if (extension != NULL && extension[0] == '\0') {
+	extension = NULL;
+    }
+    return extension;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ParseSubcommandOptions --
+ *
+ *	This function is invoked to process one of the options which may be
+ *	specified for the photo image subcommands, namely, -from, -to, -zoom,
+ *	-subsample, -format, -shrink, and -compositingrule.
+ *
+ * Results:
+ *	A standard Tcl result.
+ *
+ * Side effects:
+ *	Fields in *optPtr get filled in.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ParseSubcommandOptions(
+    struct SubcommandOptions *optPtr,
+				/* Information about the options specified and
+				 * the values given is returned here. */
+    Tcl_Interp *interp,		/* Interpreter to use for reporting errors. */
+    int allowedOptions,		/* Indicates which options are valid for the
+				 * current command. */
+    int *optIndexPtr,		/* Points to a variable containing the current
+				 * index in objv; this variable is updated by
+				 * this function. */
+    int objc,			/* Number of arguments in objv[]. */
+    Tcl_Obj *const objv[])	/* Arguments to be parsed. */
+{
+    static const char *const compositingRules[] = {
+	"overlay", "set",	/* Note that these must match the
+				 * TK_PHOTO_COMPOSITE_* constants. */
+	NULL
+    };
+    int index, c, bit, currentBit, length;
+    int values[4], numValues, maxValues, argIndex;
+    const char *option, *expandedOption, *needed;
+    const char *const *listPtr;
+    Tcl_Obj *msgObj;
+
+    for (index = *optIndexPtr; index < objc; *optIndexPtr = ++index) {
+	/*
+	 * We can have one value specified without an option; it goes into
+	 * optPtr->name.
+	 */
+
+	expandedOption = option = Tcl_GetStringFromObj(objv[index], &length);
+	if (option[0] != '-') {
+	    if (optPtr->name == NULL) {
+		optPtr->name = objv[index];
+		continue;
+	    }
+	    break;
+	}
+
+	/*
+	 * Work out which option this is.
+	 */
+
+	c = option[0];
+	bit = 0;
+	currentBit = 1;
+	for (listPtr = optionNames; *listPtr != NULL; ++listPtr) {
+	    if ((c == *listPtr[0])
+		    && (strncmp(option, *listPtr, (size_t) length) == 0)) {
+		expandedOption = *listPtr;
+		if (bit != 0) {
+		    goto unknownOrAmbiguousOption;
+		}
+		bit = currentBit;
+	    }
+	    currentBit <<= 1;
+	}
+
+	/*
+	 * If this option is not recognized and allowed, put an error message
+	 * in the interpreter and return.
+	 */
+
+	if (!(allowedOptions & bit)) {
+	    goto unknownOrAmbiguousOption;
+	}
+
+	/*
+	 * For the -from, -to, -zoom and -subsample options, parse the values
+	 * given. Report an error if too few or too many values are given.
+	 */
+
+	if (bit == OPT_BACKGROUND) {
+	    /*
+	     * The -background option takes a single XColor value.
+	     */
+
+	    if (index + 1 >= objc) {
+		goto oneValueRequired;
+	    }
+	    *optIndexPtr = ++index;
+	    optPtr->background = Tk_GetColor(interp, Tk_MainWindow(interp),
+		    Tk_GetUid(Tcl_GetString(objv[index])));
+	    if (!optPtr->background) {
+		return TCL_ERROR;
+	    }
+	} else if (bit == OPT_FORMAT) {
+	    /*
+	     * The -format option takes a single string value. Note that
+	     * parsing this is outside the scope of this function.
+	     */
+
+	    if (index + 1 >= objc) {
+		goto oneValueRequired;
+	    }
+	    *optIndexPtr = ++index;
+	    optPtr->format = objv[index];
+	} else if (bit == OPT_COMPOSITE) {
+	    /*
+	     * The -compositingrule option takes a single value from a
+	     * well-known set.
+	     */
+
+	    if (index + 1 >= objc) {
+		goto oneValueRequired;
+	    }
+	    index++;
+	    if (Tcl_GetIndexFromObj(interp, objv[index], compositingRules,
+		    "compositing rule", 0, &optPtr->compositingRule)
+		    != TCL_OK) {
+		return TCL_ERROR;
+	    }
+	    *optIndexPtr = index;
+	} else if ((bit != OPT_SHRINK) && (bit != OPT_GRAYSCALE)) {
+	    const char *val;
+
+	    maxValues = ((bit == OPT_FROM) || (bit == OPT_TO)) ? 4 : 2;
+	    argIndex = index + 1;
+	    for (numValues = 0; numValues < maxValues; ++numValues) {
+		if (argIndex >= objc) {
+		    break;
+		}
+		val = Tcl_GetString(objv[argIndex]);
+		if ((argIndex < objc) && (isdigit(UCHAR(val[0]))
+			|| ((val[0] == '-') && isdigit(UCHAR(val[1]))))) {
+		    if (Tcl_GetInt(interp, val, &values[numValues])
+			    != TCL_OK) {
+			return TCL_ERROR;
+		    }
+		} else {
+		    break;
+		}
+		argIndex++;
+	    }
+
+	    if (numValues == 0) {
+		goto manyValuesRequired;
+	    }
+	    *optIndexPtr = (index += numValues);
+
+	    /*
+	     * Y values default to the corresponding X value if not specified.
+	     */
+
+	    if (numValues == 1) {
+		values[1] = values[0];
+	    }
+	    if (numValues == 3) {
+		values[3] = values[2];
+	    }
+
+	    /*
+	     * Check the values given and put them in the appropriate field of
+	     * the SubcommandOptions structure.
+	     */
+
+	    switch (bit) {
+	    case OPT_FROM:
+		if ((values[0] < 0) || (values[1] < 0) || ((numValues > 2)
+			&& ((values[2] < 0) || (values[3] < 0)))) {
+		    needed = "non-negative";
+		    goto numberOutOfRange;
+		}
+		if (numValues <= 2) {
+		    optPtr->fromX = values[0];
+		    optPtr->fromY = values[1];
+		    optPtr->fromX2 = -1;
+		    optPtr->fromY2 = -1;
+		} else {
+		    optPtr->fromX = MIN(values[0], values[2]);
+		    optPtr->fromY = MIN(values[1], values[3]);
+		    optPtr->fromX2 = MAX(values[0], values[2]);
+		    optPtr->fromY2 = MAX(values[1], values[3]);
+		}
+		break;
+	    case OPT_SUBSAMPLE:
+		optPtr->subsampleX = values[0];
+		optPtr->subsampleY = values[1];
+		break;
+	    case OPT_TO:
+		if ((values[0] < 0) || (values[1] < 0) || ((numValues > 2)
+			&& ((values[2] < 0) || (values[3] < 0)))) {
+		    needed = "non-negative";
+		    goto numberOutOfRange;
+		}
+		if (numValues <= 2) {
+		    optPtr->toX = values[0];
+		    optPtr->toY = values[1];
+		    optPtr->toX2 = -1;
+		    optPtr->toY2 = -1;
+		} else {
+		    optPtr->toX = MIN(values[0], values[2]);
+		    optPtr->toY = MIN(values[1], values[3]);
+		    optPtr->toX2 = MAX(values[0], values[2]);
+		    optPtr->toY2 = MAX(values[1], values[3]);
+		}
+		break;
+	    case OPT_ZOOM:
+		if ((values[0] <= 0) || (values[1] <= 0)) {
+		    needed = "positive";
+		    goto numberOutOfRange;
+		}
+		optPtr->zoomX = values[0];
+		optPtr->zoomY = values[1];
+		break;
+	    }
+	}
+
+	/*
+	 * Remember that we saw this option.
+	 */
+
+	optPtr->options |= bit;
+    }
+    return TCL_OK;
+
+    /*
+     * Exception generation.
+     */
+
+  oneValueRequired:
+    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+	    "the \"%s\" option requires a value", expandedOption));
+    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "MISSING_VALUE", NULL);
+    return TCL_ERROR;
+
+  manyValuesRequired:
+    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+	    "the \"%s\" option requires one %s integer values",
+	    expandedOption, (maxValues == 2) ? "or two": "to four"));
+    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "MISSING_VALUE", NULL);
+    return TCL_ERROR;
+
+  numberOutOfRange:
+    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+	    "value(s) for the %s option must be %s", expandedOption, needed));
+    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "BAD_VALUE", NULL);
+    return TCL_ERROR;
+
+  unknownOrAmbiguousOption:
+    msgObj = Tcl_ObjPrintf("unrecognized option \"%s\": must be ", option);
+    bit = 1;
+    for (listPtr = optionNames; *listPtr != NULL; ++listPtr) {
+	if (allowedOptions & bit) {
+	    if (allowedOptions & (bit - 1)) {
+		if (allowedOptions & ~((bit << 1) - 1)) {
+		    Tcl_AppendToObj(msgObj, ", ", -1);
+		} else {
+		    Tcl_AppendToObj(msgObj, ", or ", -1);
+		}
+	    }
+	    Tcl_AppendToObj(msgObj, *listPtr, -1);
+	}
+	bit <<= 1;
+    }
+    Tcl_SetObjResult(interp, msgObj);
+    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO", "BAD_OPTION", NULL);
+    return TCL_ERROR;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgPhotoConfigureMaster --
+ *
+ *	This function is called when a photo image is created or reconfigured.
+ *	It processes configuration options and resets any instances of the
+ *	image.
+ *
+ * Results:
+ *	A standard Tcl return value. If TCL_ERROR is returned then an error
+ *	message is left in the masterPtr->interp's result.
+ *
+ * Side effects:
+ *	Existing instances of the image will be redisplayed to match the new
+ *	configuration options.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ImgPhotoConfigureMaster(
+    Tcl_Interp *interp,		/* Interpreter to use for reporting errors. */
+    PhotoMaster *masterPtr,	/* Pointer to data structure describing
+				 * overall photo image to (re)configure. */
+    int objc,			/* Number of entries in objv. */
+    Tcl_Obj *const objv[],	/* Pairs of configuration options for image. */
+    int flags)			/* Flags to pass to Tk_ConfigureWidget, such
+				 * as TK_CONFIG_ARGV_ONLY. */
+{
+    PhotoInstance *instancePtr;
+    const char *oldFileString, *oldPaletteString;
+    Tcl_Obj *oldData, *data = NULL, *oldFormat, *format = NULL;
+    Tcl_Obj *tempdata, *tempformat;
+    int length, i, j, result, imageWidth, imageHeight, oldformat;
+    double oldGamma;
+    Tcl_Channel chan;
+    Tk_PhotoImageFormat *imageFormat;
+    const char **args;
+
+    args = ckalloc((objc + 1) * sizeof(char *));
+    for (i = 0, j = 0; i < objc; i++,j++) {
+	args[j] = Tcl_GetStringFromObj(objv[i], &length);
+	if ((length > 1) && (args[j][0] == '-')) {
+	    if ((args[j][1] == 'd') &&
+		    !strncmp(args[j], "-data", (size_t) length)) {
+		if (++i < objc) {
+		    data = objv[i];
+		    j--;
+		} else {
+		    ckfree(args);
+		    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			    "value for \"-data\" missing", -1));
+		    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			    "MISSING_VALUE", NULL);
+		    return TCL_ERROR;
+		}
+	    } else if ((args[j][1] == 'f') &&
+		    !strncmp(args[j], "-format", (size_t) length)) {
+		if (++i < objc) {
+		    format = objv[i];
+		    j--;
+		} else {
+		    ckfree(args);
+		    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			    "value for \"-format\" missing", -1));
+		    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			    "MISSING_VALUE", NULL);
+		    return TCL_ERROR;
+		}
+	    }
+	}
+    }
+
+    /*
+     * Save the current values for fileString and dataString, so we can tell
+     * if the user specifies them anew. IMPORTANT: if the format changes we
+     * have to interpret "-file" and "-data" again as well! It might be that
+     * the format string influences how "-data" or "-file" is interpreted.
+     */
+
+    oldFileString = masterPtr->fileString;
+    if (oldFileString == NULL) {
+	oldData = masterPtr->dataString;
+	if (oldData != NULL) {
+	    Tcl_IncrRefCount(oldData);
+	}
+    } else {
+	oldData = NULL;
+    }
+    oldFormat = masterPtr->format;
+    if (oldFormat != NULL) {
+	Tcl_IncrRefCount(oldFormat);
+    }
+    oldPaletteString = masterPtr->palette;
+    oldGamma = masterPtr->gamma;
+
+    /*
+     * Process the configuration options specified.
+     */
+
+    if (Tk_ConfigureWidget(interp, Tk_MainWindow(interp), configSpecs,
+	    j, args, (char *) masterPtr, flags) != TCL_OK) {
+	ckfree(args);
+	goto errorExit;
+    }
+    ckfree(args);
+
+    /*
+     * Regard the empty string for -file, -data or -format as the null value.
+     */
+
+    if ((masterPtr->fileString != NULL) && (masterPtr->fileString[0] == 0)) {
+	ckfree(masterPtr->fileString);
+	masterPtr->fileString = NULL;
+    }
+    if (data) {
+	/*
+	 * Force into ByteArray format, which most (all) image handlers will
+	 * use anyway. Empty length means ignore the -data option.
+	 */
+
+	(void) Tcl_GetByteArrayFromObj(data, &length);
+	if (length) {
+	    Tcl_IncrRefCount(data);
+	} else {
+	    data = NULL;
+	}
+	if (masterPtr->dataString) {
+	    Tcl_DecrRefCount(masterPtr->dataString);
+	}
+	masterPtr->dataString = data;
+    }
+    if (format) {
+	/*
+	 * Stringify to ignore -format "". It may come in as a list or other
+	 * object.
+	 */
+
+	(void) Tcl_GetStringFromObj(format, &length);
+	if (length) {
+	    Tcl_IncrRefCount(format);
+	} else {
+	    format = NULL;
+	}
+	if (masterPtr->format) {
+	    Tcl_DecrRefCount(masterPtr->format);
+	}
+	masterPtr->format = format;
+    }
+    /*
+     * Set the image to the user-requested size, if any, and make sure storage
+     * is correctly allocated for this image.
+     */
+
+    if (ImgPhotoSetSize(masterPtr, masterPtr->width,
+	    masterPtr->height) != TCL_OK) {
+	Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+	Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	goto errorExit;
+    }
+
+    /*
+     * Read in the image from the file or string if the user has specified the
+     * -file or -data option.
+     */
+
+    if ((masterPtr->fileString != NULL)
+	    && ((masterPtr->fileString != oldFileString)
+	    || (masterPtr->format != oldFormat))) {
+	/*
+	 * Prevent file system access in a safe interpreter.
+	 */
+
+	if (Tcl_IsSafe(interp)) {
+	    Tcl_ResetResult(interp);
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "can't get image from a file in a safe interpreter",
+		    -1));
+	    Tcl_SetErrorCode(interp, "TK", "SAFE", "PHOTO_FILE", NULL);
+	    goto errorExit;
+	}
+
+	chan = Tcl_OpenFileChannel(interp, masterPtr->fileString, "r", 0);
+	if (chan == NULL) {
+	    goto errorExit;
+	}
+
+	/*
+	 * -translation binary also sets -encoding binary
+	 */
+
+	if ((Tcl_SetChannelOption(interp, chan,
+		"-translation", "binary") != TCL_OK) ||
+		(MatchFileFormat(interp, chan, masterPtr->fileString,
+			masterPtr->format, &imageFormat, &imageWidth,
+			&imageHeight, &oldformat) != TCL_OK)) {
+	    Tcl_Close(NULL, chan);
+	    goto errorExit;
+	}
+	result = ImgPhotoSetSize(masterPtr, imageWidth, imageHeight);
+	if (result != TCL_OK) {
+	    Tcl_Close(NULL, chan);
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+	    Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	    goto errorExit;
+	}
+	tempformat = masterPtr->format;
+	if (oldformat && tempformat) {
+	    tempformat = (Tcl_Obj *) Tcl_GetString(tempformat);
+	}
+	result = imageFormat->fileReadProc(interp, chan,
+		masterPtr->fileString, tempformat, (Tk_PhotoHandle) masterPtr,
+		0, 0, imageWidth, imageHeight, 0, 0);
+	Tcl_Close(NULL, chan);
+	if (result != TCL_OK) {
+	    goto errorExit;
+	}
+
+	Tcl_ResetResult(interp);
+	masterPtr->flags |= IMAGE_CHANGED;
+    }
+
+    if ((masterPtr->fileString == NULL) && (masterPtr->dataString != NULL)
+	    && ((masterPtr->dataString != oldData)
+		    || (masterPtr->format != oldFormat))) {
+
+	if (MatchStringFormat(interp, masterPtr->dataString,
+		masterPtr->format, &imageFormat, &imageWidth,
+		&imageHeight, &oldformat) != TCL_OK) {
+	    goto errorExit;
+	}
+	if (ImgPhotoSetSize(masterPtr, imageWidth, imageHeight) != TCL_OK) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+	    Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	    goto errorExit;
+	}
+	tempformat = masterPtr->format;
+	tempdata = masterPtr->dataString;
+	if (oldformat) {
+	    if (tempformat) {
+		tempformat = (Tcl_Obj *) Tcl_GetString(tempformat);
+	    }
+	    tempdata = (Tcl_Obj *) Tcl_GetString(tempdata);
+	}
+	if (imageFormat->stringReadProc(interp, tempdata, tempformat,
+		(Tk_PhotoHandle) masterPtr, 0, 0, imageWidth, imageHeight,
+		0, 0) != TCL_OK) {
+	    goto errorExit;
+	}
+
+	Tcl_ResetResult(interp);
+	masterPtr->flags |= IMAGE_CHANGED;
+    }
+
+    /*
+     * Enforce a reasonable value for gamma.
+     */
+
+    if (masterPtr->gamma <= 0) {
+	masterPtr->gamma = 1.0;
+    }
+
+    if ((masterPtr->gamma != oldGamma)
+	    || (masterPtr->palette != oldPaletteString)) {
+	masterPtr->flags |= IMAGE_CHANGED;
+    }
+
+    /*
+     * Cycle through all of the instances of this image, regenerating the
+     * information for each instance. Then force the image to be redisplayed
+     * everywhere that it is used.
+     */
+
+    for (instancePtr = masterPtr->instancePtr; instancePtr != NULL;
+	    instancePtr = instancePtr->nextPtr) {
+	TkImgPhotoConfigureInstance(instancePtr);
+    }
+
+    /*
+     * Inform the generic image code that the image has (potentially) changed.
+     */
+
+    Tk_ImageChanged(masterPtr->tkMaster, 0, 0, masterPtr->width,
+	    masterPtr->height, masterPtr->width, masterPtr->height);
+    masterPtr->flags &= ~IMAGE_CHANGED;
+
+    if (oldData != NULL) {
+	Tcl_DecrRefCount(oldData);
+    }
+    if (oldFormat != NULL) {
+	Tcl_DecrRefCount(oldFormat);
+    }
+
+    ToggleComplexAlphaIfNeeded(masterPtr);
+
+    return TCL_OK;
+
+  errorExit:
+    if (oldData != NULL) {
+	Tcl_DecrRefCount(oldData);
+    }
+    if (oldFormat != NULL) {
+	Tcl_DecrRefCount(oldFormat);
+    }
+    return TCL_ERROR;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ToggleComplexAlphaIfNeeded --
+ *
+ *	This function is called when an image is modified to check if any
+ *	partially transparent pixels exist, which requires blending instead of
+ *	straight copy.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	(Re)sets COMPLEX_ALPHA flag of master.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ToggleComplexAlphaIfNeeded(
+    PhotoMaster *mPtr)
+{
+    size_t len = (size_t)MAX(mPtr->userWidth, mPtr->width) *
+	    (size_t)MAX(mPtr->userHeight, mPtr->height) * 4;
+    unsigned char *c = mPtr->pix32;
+    unsigned char *end = c + len;
+
+    /*
+     * Set the COMPLEX_ALPHA flag if we have an image with partially
+     * transparent bits.
+     */
+
+    mPtr->flags &= ~COMPLEX_ALPHA;
+    if (c == NULL) {
+	return 0;
+    }
+    c += 3;			/* Start at first alpha byte. */
+    for (; c < end; c += 4) {
+	if (*c && *c != 255) {
+     	    mPtr->flags |= COMPLEX_ALPHA;
+	    break;
+	}
+    }
+    return (mPtr->flags & COMPLEX_ALPHA);
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgPhotoDelete --
+ *
+ *	This function is called by the image code to delete the master
+ *	structure for an image.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	Resources associated with the image get freed.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+ImgPhotoDelete(
+    ClientData masterData)	/* Pointer to PhotoMaster structure for image.
+				 * Must not have any more instances. */
+{
+    PhotoMaster *masterPtr = masterData;
+    PhotoInstance *instancePtr;
+
+    while ((instancePtr = masterPtr->instancePtr) != NULL) {
+	if (instancePtr->refCount > 0) {
+	    Tcl_Panic("tried to delete photo image when instances still exist");
+	}
+	Tcl_CancelIdleCall(TkImgDisposeInstance, instancePtr);
+	TkImgDisposeInstance(instancePtr);
+    }
+    masterPtr->tkMaster = NULL;
+    if (masterPtr->imageCmd != NULL) {
+	Tcl_DeleteCommandFromToken(masterPtr->interp, masterPtr->imageCmd);
+    }
+    if (masterPtr->pix32 != NULL) {
+	ckfree(masterPtr->pix32);
+    }
+    if (masterPtr->validRegion != NULL) {
+	TkDestroyRegion(masterPtr->validRegion);
+    }
+    if (masterPtr->dataString != NULL) {
+	Tcl_DecrRefCount(masterPtr->dataString);
+    }
+    if (masterPtr->format != NULL) {
+	Tcl_DecrRefCount(masterPtr->format);
+    }
+    Tk_FreeOptions(configSpecs, (char *) masterPtr, NULL, 0);
+    ckfree(masterPtr);
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgPhotoCmdDeletedProc --
+ *
+ *	This function is invoked when the image command for an image is
+ *	deleted. It deletes the image.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The image is deleted.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static void
+ImgPhotoCmdDeletedProc(
+    ClientData clientData)	/* Pointer to PhotoMaster structure for
+				 * image. */
+{
+    PhotoMaster *masterPtr = clientData;
+
+    masterPtr->imageCmd = NULL;
+    if (masterPtr->tkMaster != NULL) {
+	Tk_DeleteImage(masterPtr->interp, Tk_NameOfImage(masterPtr->tkMaster));
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgPhotoSetSize --
+ *
+ *	This function reallocates the image storage and instance pixmaps for a
+ *	photo image, as necessary, to change the image's size to `width' x
+ *	`height' pixels.
+ *
+ * Results:
+ *	TCL_OK if successful, TCL_ERROR if failure occurred (currently just
+ *	with memory allocation.)
+ *
+ * Side effects:
+ *	Storage gets reallocated, for the master and all its instances.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ImgPhotoSetSize(
+    PhotoMaster *masterPtr,
+    int width, int height)
+{
+    unsigned char *newPix32 = NULL;
+    int h, offset, pitch;
+    unsigned char *srcPtr, *destPtr;
+    XRectangle validBox, clipBox;
+    TkRegion clipRegion;
+    PhotoInstance *instancePtr;
+
+    if (masterPtr->userWidth > 0) {
+	width = masterPtr->userWidth;
+    }
+    if (masterPtr->userHeight > 0) {
+	height = masterPtr->userHeight;
+    }
+
+    if (width > INT_MAX / 4) {
+	/* Pitch overflows int */
+	return TCL_ERROR;
+    }
+    pitch = width * 4;
+
+    /*
+     * Test if we're going to (re)allocate the main buffer now, so that any
+     * failures will leave the photo unchanged.
+     */
+
+    if ((width != masterPtr->width) || (height != masterPtr->height)
+	    || (masterPtr->pix32 == NULL)) {
+	unsigned newPixSize;
+
+	if (pitch && height > (int)(UINT_MAX / pitch)) {
+	    return TCL_ERROR;
+	}
+	newPixSize = height * pitch;
+
+	/*
+	 * Some mallocs() really hate allocating zero bytes. [Bug 619544]
+	 */
+
+	if (newPixSize == 0) {
+	    newPix32 = NULL;
+	} else {
+	    newPix32 = attemptckalloc(newPixSize);
+	    if (newPix32 == NULL) {
+		return TCL_ERROR;
+	    }
+	}
+    }
+
+    /*
+     * We have to trim the valid region if it is currently larger than the new
+     * image size.
+     */
+
+    TkClipBox(masterPtr->validRegion, &validBox);
+    if ((validBox.x + validBox.width > width)
+	    || (validBox.y + validBox.height > height)) {
+	clipBox.x = 0;
+	clipBox.y = 0;
+	clipBox.width = width;
+	clipBox.height = height;
+	clipRegion = TkCreateRegion();
+	TkUnionRectWithRegion(&clipBox, clipRegion, clipRegion);
+	TkIntersectRegion(masterPtr->validRegion, clipRegion,
+		masterPtr->validRegion);
+	TkDestroyRegion(clipRegion);
+	TkClipBox(masterPtr->validRegion, &validBox);
+    }
+
+    /*
+     * Use the reallocated storage (allocation above) for the 32-bit image and
+     * copy over valid regions. Note that this test is true precisely when the
+     * allocation has already been done.
+     */
+
+    if (newPix32 != NULL) {
+	/*
+	 * Zero the new array. The dithering code shouldn't read the areas
+	 * outside validBox, but they might be copied to another photo image
+	 * or written to a file.
+	 */
+
+	if ((masterPtr->pix32 != NULL)
+	    && ((width == masterPtr->width) || (width == validBox.width))) {
+	    if (validBox.y > 0) {
+		memset(newPix32, 0, ((size_t) validBox.y * pitch));
+	    }
+	    h = validBox.y + validBox.height;
+	    if (h < height) {
+		memset(newPix32 + h*pitch, 0, ((size_t) (height - h) * pitch));
+	    }
+	} else {
+	    memset(newPix32, 0, ((size_t)height * pitch));
+	}
+
+	if (masterPtr->pix32 != NULL) {
+	    /*
+	     * Copy the common area over to the new array array and free the
+	     * old array.
+	     */
+
+	    if (width == masterPtr->width) {
+
+		/*
+		 * The region to be copied is contiguous.
+		 */
+
+		offset = validBox.y * pitch;
+		memcpy(newPix32 + offset, masterPtr->pix32 + offset,
+			((size_t)validBox.height * pitch));
+
+	    } else if ((validBox.width > 0) && (validBox.height > 0)) {
+		/*
+		 * Area to be copied is not contiguous - copy line by line.
+		 */
+
+		destPtr = newPix32 + (validBox.y * width + validBox.x) * 4;
+		srcPtr = masterPtr->pix32 + (validBox.y * masterPtr->width
+			+ validBox.x) * 4;
+		for (h = validBox.height; h > 0; h--) {
+		    memcpy(destPtr, srcPtr, ((size_t)validBox.width * 4));
+		    destPtr += width * 4;
+		    srcPtr += masterPtr->width * 4;
+		}
+	    }
+
+	    ckfree(masterPtr->pix32);
+	}
+
+	masterPtr->pix32 = newPix32;
+	masterPtr->width = width;
+	masterPtr->height = height;
+
+	/*
+	 * Dithering will be correct up to the end of the last pre-existing
+	 * complete scanline.
+	 */
+
+	if ((validBox.x > 0) || (validBox.y > 0)) {
+	    masterPtr->ditherX = 0;
+	    masterPtr->ditherY = 0;
+	} else if (validBox.width == width) {
+	    if ((int) validBox.height < masterPtr->ditherY) {
+		masterPtr->ditherX = 0;
+		masterPtr->ditherY = validBox.height;
+	    }
+	} else if ((masterPtr->ditherY > 0)
+		|| ((int) validBox.width < masterPtr->ditherX)) {
+	    masterPtr->ditherX = validBox.width;
+	    masterPtr->ditherY = 0;
+	}
+    }
+
+    ToggleComplexAlphaIfNeeded(masterPtr);
+
+    /*
+     * Now adjust the sizes of the pixmaps for all of the instances.
+     */
+
+    for (instancePtr = masterPtr->instancePtr; instancePtr != NULL;
+	    instancePtr = instancePtr->nextPtr) {
+	TkImgPhotoInstanceSetSize(instancePtr);
+    }
+
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * MatchFileFormat --
+ *
+ *	This function is called to find a photo image file format handler
+ *	which can parse the image data in the given file. If a user-specified
+ *	format string is provided, only handlers whose names match a prefix of
+ *	the format string are tried.
+ *
+ * Results:
+ *	A standard TCL return value. If the return value is TCL_OK, a pointer
+ *	to the image format record is returned in *imageFormatPtr, and the
+ *	width and height of the image are returned in *widthPtr and
+ *	*heightPtr.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+MatchFileFormat(
+    Tcl_Interp *interp,		/* Interpreter to use for reporting errors. */
+    Tcl_Channel chan,		/* The image file, open for reading. */
+    const char *fileName,	/* The name of the image file. */
+    Tcl_Obj *formatObj,		/* User-specified format string, or NULL. */
+    Tk_PhotoImageFormat **imageFormatPtr,
+				/* A pointer to the photo image format record
+				 * is returned here. */
+    int *widthPtr, int *heightPtr,
+				/* The dimensions of the image are returned
+				 * here. */
+    int *oldformat)		/* Returns 1 if the old image API is used. */
+{
+    int matched = 0, useoldformat = 0;
+    Tk_PhotoImageFormat *formatPtr;
+    ThreadSpecificData *tsdPtr =
+	    Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));
+    const char *formatString = NULL;
+
+    if (formatObj) {
+	formatString = Tcl_GetString(formatObj);
+    }
+
+    /*
+     * Scan through the table of file format handlers to find one which can
+     * handle the image.
+     */
+
+    for (formatPtr = tsdPtr->formatList; formatPtr != NULL;
+	    formatPtr = formatPtr->nextPtr) {
+	if (formatObj != NULL) {
+	    if (strncasecmp(formatString,
+		    formatPtr->name, strlen(formatPtr->name)) != 0) {
+		continue;
+	    }
+	    matched = 1;
+	    if (formatPtr->fileMatchProc == NULL) {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"-file option isn't supported for %s images",
+			formatString));
+		Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			"NOT_FILE_FORMAT", NULL);
+		return TCL_ERROR;
+	    }
+	}
+	if (formatPtr->fileMatchProc != NULL) {
+	    (void) Tcl_Seek(chan, Tcl_LongAsWide(0L), SEEK_SET);
+
+	    if (formatPtr->fileMatchProc(chan, fileName, formatObj,
+		    widthPtr, heightPtr, interp)) {
+		if (*widthPtr < 1) {
+		    *widthPtr = 1;
+		}
+		if (*heightPtr < 1) {
+		    *heightPtr = 1;
+		}
+		break;
+	    }
+	}
+    }
+    if (formatPtr == NULL) {
+	useoldformat = 1;
+	for (formatPtr = tsdPtr->oldFormatList; formatPtr != NULL;
+		formatPtr = formatPtr->nextPtr) {
+	    if (formatString != NULL) {
+		if (strncasecmp(formatString,
+			formatPtr->name, strlen(formatPtr->name)) != 0) {
+		    continue;
+		}
+		matched = 1;
+		if (formatPtr->fileMatchProc == NULL) {
+		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			    "-file option isn't supported for %s images",
+			    formatString));
+		    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			    "NOT_FILE_FORMAT", NULL);
+		    return TCL_ERROR;
+		}
+	    }
+	    if (formatPtr->fileMatchProc != NULL) {
+		(void) Tcl_Seek(chan, Tcl_LongAsWide(0L), SEEK_SET);
+		if (formatPtr->fileMatchProc(chan, fileName, (Tcl_Obj *)
+			formatString, widthPtr, heightPtr, interp)) {
+		    if (*widthPtr < 1) {
+			*widthPtr = 1;
+		    }
+		    if (*heightPtr < 1) {
+			*heightPtr = 1;
+		    }
+		    break;
+		}
+	    }
+	}
+    }
+
+    if (formatPtr == NULL) {
+	if ((formatObj != NULL) && !matched) {
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "image file format \"%s\" is not supported",
+		    formatString));
+	    Tcl_SetErrorCode(interp, "TK", "LOOKUP", "PHOTO_FORMAT",
+		    formatString, NULL);
+	} else {
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "couldn't recognize data in image file \"%s\"",
+		    fileName));
+	    Tcl_SetErrorCode(interp, "TK", "PHOTO", "IMAGE",
+		    "UNRECOGNIZED_DATA", NULL);
+	}
+	return TCL_ERROR;
+    }
+
+    *imageFormatPtr = formatPtr;
+    *oldformat = useoldformat;
+    (void) Tcl_Seek(chan, Tcl_LongAsWide(0L), SEEK_SET);
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * MatchStringFormat --
+ *
+ *	This function is called to find a photo image file format handler
+ *	which can parse the image data in the given string. If a
+ *	user-specified format string is provided, only handlers whose names
+ *	match a prefix of the format string are tried.
+ *
+ * Results:
+ *	A standard TCL return value. If the return value is TCL_OK, a pointer
+ *	to the image format record is returned in *imageFormatPtr, and the
+ *	width and height of the image are returned in *widthPtr and
+ *	*heightPtr.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+MatchStringFormat(
+    Tcl_Interp *interp,		/* Interpreter to use for reporting errors. */
+    Tcl_Obj *data,		/* Object containing the image data. */
+    Tcl_Obj *formatObj,		/* User-specified format string, or NULL. */
+    Tk_PhotoImageFormat **imageFormatPtr,
+				/* A pointer to the photo image format record
+				 * is returned here. */
+    int *widthPtr, int *heightPtr,
+				/* The dimensions of the image are returned
+				 * here. */
+    int *oldformat)		/* Returns 1 if the old image API is used. */
+{
+    int matched = 0, useoldformat = 0;
+    Tk_PhotoImageFormat *formatPtr;
+    ThreadSpecificData *tsdPtr =
+	    Tcl_GetThreadData(&dataKey, sizeof(ThreadSpecificData));
+    const char *formatString = NULL;
+
+    if (formatObj) {
+	formatString = Tcl_GetString(formatObj);
+    }
+
+    /*
+     * Scan through the table of file format handlers to find one which can
+     * handle the image.
+     */
+
+    for (formatPtr = tsdPtr->formatList; formatPtr != NULL;
+	    formatPtr = formatPtr->nextPtr) {
+	if (formatObj != NULL) {
+	    if (strncasecmp(formatString,
+		    formatPtr->name, strlen(formatPtr->name)) != 0) {
+		continue;
+	    }
+	    matched = 1;
+	    if (formatPtr->stringMatchProc == NULL) {
+		Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			"-data option isn't supported for %s images",
+			formatString));
+		Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			"NOT_DATA_FORMAT", NULL);
+		return TCL_ERROR;
+	    }
+	}
+	if ((formatPtr->stringMatchProc != NULL)
+		&& (formatPtr->stringReadProc != NULL)
+		&& formatPtr->stringMatchProc(data, formatObj,
+			widthPtr, heightPtr, interp)) {
+	    break;
+	}
+    }
+
+    if (formatPtr == NULL) {
+	useoldformat = 1;
+	for (formatPtr = tsdPtr->oldFormatList; formatPtr != NULL;
+		formatPtr = formatPtr->nextPtr) {
+	    if (formatObj != NULL) {
+		if (strncasecmp(formatString,
+			formatPtr->name, strlen(formatPtr->name)) != 0) {
+		    continue;
+		}
+		matched = 1;
+		if (formatPtr->stringMatchProc == NULL) {
+		    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+			    "-data option isn't supported for %s images",
+			    formatString));
+		    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+			    "NOT_DATA_FORMAT", NULL);
+		    return TCL_ERROR;
+		}
+	    }
+	    if ((formatPtr->stringMatchProc != NULL)
+		    && (formatPtr->stringReadProc != NULL)
+		    && formatPtr->stringMatchProc(
+			    (Tcl_Obj *) Tcl_GetString(data),
+			    (Tcl_Obj *) formatString,
+			    widthPtr, heightPtr, interp)) {
+		break;
+	    }
+	}
+    }
+    if (formatPtr == NULL) {
+	if ((formatObj != NULL) && !matched) {
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "image format \"%s\" is not supported", formatString));
+	    Tcl_SetErrorCode(interp, "TK", "LOOKUP", "PHOTO_FORMAT",
+		    formatString, NULL);
+	} else {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    "couldn't recognize image data", -1));
+	    Tcl_SetErrorCode(interp, "TK", "IMAGE", "PHOTO",
+		    "UNRECOGNIZED_DATA", NULL);
+	}
+	return TCL_ERROR;
+    }
+
+    *imageFormatPtr = formatPtr;
+    *oldformat = useoldformat;
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_FindPhoto --
+ *
+ *	This function is called to get an opaque handle (actually a
+ *	PhotoMaster *) for a given image, which can be used in subsequent
+ *	calls to Tk_PhotoPutBlock, etc. The `name' parameter is the name of
+ *	the image.
+ *
+ * Results:
+ *	The handle for the photo image, or NULL if there is no photo image
+ *	with the name given.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+Tk_PhotoHandle
+Tk_FindPhoto(
+    Tcl_Interp *interp,		/* Interpreter (application) in which image
+				 * exists. */
+    const char *imageName)	/* Name of the desired photo image. */
+{
+    const Tk_ImageType *typePtr;
+    ClientData clientData =
+	    Tk_GetImageMasterData(interp, imageName, &typePtr);
+
+    if ((typePtr == NULL) || (typePtr->name != tkPhotoImageType.name)) {
+	return NULL;
+    }
+    return clientData;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoPutBlock --
+ *
+ *	This function is called to put image data into a photo image.
+ *
+ * Results:
+ *	A standard Tcl result code.
+ *
+ * Side effects:
+ *	The image data is stored. The image may be expanded. The Tk image code
+ *	is informed that the image has changed. If the result code is
+ *	TCL_ERROR, an error message will be placed in the interpreter (if
+ *	non-NULL).
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+Tk_PhotoPutBlock(
+    Tcl_Interp *interp,		/* Interpreter for passing back error
+				 * messages, or NULL. */
+    Tk_PhotoHandle handle,	/* Opaque handle for the photo image to be
+				 * updated. */
+    register Tk_PhotoImageBlock *blockPtr,
+				/* Pointer to a structure describing the pixel
+				 * data to be copied into the image. */
+    int x, int y,		/* Coordinates of the top-left pixel to be
+				 * updated in the image. */
+    int width, int height,	/* Dimensions of the area of the image to be
+				 * updated. */
+    int compRule)		/* Compositing rule to use when processing
+				 * transparent pixels. */
+{
+    register PhotoMaster *masterPtr = (PhotoMaster *) handle;
+    int xEnd, yEnd, greenOffset, blueOffset, alphaOffset;
+    int wLeft, hLeft, wCopy, hCopy, pitch;
+    unsigned char *srcPtr, *srcLinePtr, *destPtr, *destLinePtr;
+    int sourceIsSimplePhoto = compRule & SOURCE_IS_SIMPLE_ALPHA_PHOTO;
+    XRectangle rect;
+
+    /*
+     * Zero-sized blocks never cause any changes. [Bug 3078902]
+     */
+
+    if (blockPtr->height == 0 || blockPtr->width == 0) {
+	return TCL_OK;
+    }
+
+    compRule &= ~SOURCE_IS_SIMPLE_ALPHA_PHOTO;
+
+    if ((masterPtr->userWidth != 0) && ((x + width) > masterPtr->userWidth)) {
+	width = masterPtr->userWidth - x;
+    }
+    if ((masterPtr->userHeight != 0)
+	    && ((y + height) > masterPtr->userHeight)) {
+	height = masterPtr->userHeight - y;
+    }
+    if ((width <= 0) || (height <= 0)) {
+	return TCL_OK;
+    }
+
+    xEnd = x + width;
+    yEnd = y + height;
+    if ((xEnd > masterPtr->width) || (yEnd > masterPtr->height)) {
+	int sameSrc = (blockPtr->pixelPtr == masterPtr->pix32);
+
+	if (ImgPhotoSetSize(masterPtr, MAX(xEnd, masterPtr->width),
+		MAX(yEnd, masterPtr->height)) == TCL_ERROR) {
+	    if (interp != NULL) {
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+		Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	    }
+	    return TCL_ERROR;
+	}
+	if (sameSrc) {
+	    blockPtr->pixelPtr = masterPtr->pix32;
+	    blockPtr->pitch = masterPtr->width * 4;
+	}
+    }
+
+    if ((y < masterPtr->ditherY) || ((y == masterPtr->ditherY)
+	    && (x < masterPtr->ditherX))) {
+	/*
+	 * The dithering isn't correct past the start of this block.
+	 */
+
+	masterPtr->ditherX = x;
+	masterPtr->ditherY = y;
+    }
+
+    /*
+     * If this image block could have different red, green and blue
+     * components, mark it as a color image.
+     */
+
+    greenOffset = blockPtr->offset[1] - blockPtr->offset[0];
+    blueOffset = blockPtr->offset[2] - blockPtr->offset[0];
+    alphaOffset = blockPtr->offset[3];
+    if ((alphaOffset >= blockPtr->pixelSize) || (alphaOffset < 0)) {
+	alphaOffset = 0;
+	sourceIsSimplePhoto = 1;
+    } else {
+	alphaOffset -= blockPtr->offset[0];
+    }
+    if ((greenOffset != 0) || (blueOffset != 0)) {
+	masterPtr->flags |= COLOR_IMAGE;
+    }
+
+    /*
+     * Copy the data into our local 32-bit/pixel array. If we can do it with a
+     * single memmove, we do.
+     */
+
+    destLinePtr = masterPtr->pix32 + (y * masterPtr->width + x) * 4;
+    pitch = masterPtr->width * 4;
+
+    /*
+     * Test to see if we can do the whole write in a single copy. This test is
+     * probably too restrictive. We should also be able to do a memmove if
+     * pixelSize == 3 and alphaOffset == 0. Maybe other cases too.
+     */
+
+    if ((blockPtr->pixelSize == 4)
+	    && (greenOffset == 1) && (blueOffset == 2) && (alphaOffset == 3)
+	    && (width <= blockPtr->width) && (height <= blockPtr->height)
+	    && ((height == 1) || ((x == 0) && (width == masterPtr->width)
+		&& (blockPtr->pitch == pitch)))
+	    && (compRule == TK_PHOTO_COMPOSITE_SET)) {
+	memmove(destLinePtr, blockPtr->pixelPtr + blockPtr->offset[0],
+		((size_t)height * width * 4));
+
+	/*
+	 * We know there's an alpha offset and we're setting the data, so skip
+	 * directly to the point when we recompute the photo validity region.
+	 */
+
+	goto recalculateValidRegion;
+    }
+
+    /*
+     * Copy and merge pixels according to the compositing rule.
+     */
+
+    for (hLeft = height; hLeft > 0;) {
+	int pixelSize = blockPtr->pixelSize;
+	int compRuleSet = (compRule == TK_PHOTO_COMPOSITE_SET);
+
+	srcLinePtr = blockPtr->pixelPtr + blockPtr->offset[0];
+	hCopy = MIN(hLeft, blockPtr->height);
+	hLeft -= hCopy;
+	for (; hCopy > 0; --hCopy) {
+	    /*
+	     * If the layout of the source line matches our memory layout and
+	     * we're setting, we can just copy the bytes directly, which is
+	     * much faster.
+	     */
+
+	    if ((pixelSize == 4) && (greenOffset == 1)
+		    && (blueOffset == 2) && (alphaOffset == 3)
+		    && (width <= blockPtr->width)
+		    && compRuleSet) {
+		memcpy(destLinePtr, srcLinePtr, ((size_t)width * 4));
+		srcLinePtr += blockPtr->pitch;
+		destLinePtr += pitch;
+		continue;
+	    }
+
+	    /*
+	     * Have to copy the slow way.
+	     */
+
+	    destPtr = destLinePtr;
+	    for (wLeft = width; wLeft > 0;) {
+		wCopy = MIN(wLeft, blockPtr->width);
+		wLeft -= wCopy;
+		srcPtr = srcLinePtr;
+
+		/*
+		 * But we might be lucky and be able to use fairly fast loops.
+		 * It's worth checking...
+		 */
+
+		if (alphaOffset == 0) {
+		    /*
+		     * This is the non-alpha case, so can still be fairly
+		     * fast. Note that in the non-alpha-source case, the
+		     * compositing rule doesn't apply.
+		     */
+
+		    for (; wCopy>0 ; --wCopy, srcPtr+=pixelSize) {
+			*destPtr++ = srcPtr[0];
+			*destPtr++ = srcPtr[greenOffset];
+			*destPtr++ = srcPtr[blueOffset];
+			*destPtr++ = 255;
+		    }
+		    continue;
+		} else if (compRuleSet) {
+		    /*
+		     * This is the SET compositing rule, which just replaces
+		     * what was there before with the new data. This is
+		     * another fairly fast case. No point in doing a memcpy();
+		     * the order of channels is probably wrong.
+		     */
+
+		    for (; wCopy>0 ; --wCopy, srcPtr+=pixelSize) {
+			*destPtr++ = srcPtr[0];
+			*destPtr++ = srcPtr[greenOffset];
+			*destPtr++ = srcPtr[blueOffset];
+			*destPtr++ = srcPtr[alphaOffset];
+		    }
+		    continue;
+		}
+
+		/*
+		 * Bother; need to consider the alpha value of each pixel to
+		 * know what to do.
+		 */
+
+		for (; wCopy>0 ; --wCopy, srcPtr+=pixelSize) {
+		    int alpha = srcPtr[alphaOffset];
+
+		    if (alpha == 255 || !destPtr[3]) {
+			/*
+			 * Either the source is 100% opaque, or the
+			 * destination is entirely blank. In all cases, we
+			 * just set the destination to the source.
+			 */
+
+			*destPtr++ = srcPtr[0];
+			*destPtr++ = srcPtr[greenOffset];
+			*destPtr++ = srcPtr[blueOffset];
+			*destPtr++ = alpha;
+			continue;
+		    }
+
+		    /*
+		     * Can still skip doing work if the source is 100%
+		     * transparent at this point.
+		     */
+
+		    if (alpha) {
+			int Alpha = destPtr[3];
+
+			/*
+			 * OK, there's real work to be done. Luckily, there's
+			 * a substantial literature on what to do in this
+			 * case. In particular, Porter and Duff have done a
+			 * taxonomy of compositing rules, and the right one is
+			 * the "Source Over" rule. This code implements that.
+			 */
+
+			destPtr[0] = PD_SRC_OVER(srcPtr[0], alpha, destPtr[0],
+				Alpha);
+			destPtr[1] = PD_SRC_OVER(srcPtr[greenOffset], alpha,
+				destPtr[1], Alpha);
+			destPtr[2] = PD_SRC_OVER(srcPtr[blueOffset], alpha,
+				destPtr[2], Alpha);
+			destPtr[3] = PD_SRC_OVER_ALPHA(alpha, Alpha);
+		    }
+
+		    destPtr += 4;
+		}
+	    }
+	    srcLinePtr += blockPtr->pitch;
+	    destLinePtr += pitch;
+	}
+    }
+
+    /*
+     * Add this new block to the region which specifies which data is valid.
+     */
+
+    if (alphaOffset) {
+	/*
+	 * This block is grossly inefficient. For each row in the image, it
+	 * finds each continguous string of nontransparent pixels, then marks
+	 * those areas as valid in the validRegion mask. This makes drawing
+	 * very efficient, because of the way we use X: we just say, here's
+	 * your mask, and here's your data. We need not worry about the
+	 * current background color, etc. But this costs us a lot on the image
+	 * setup. Still, image setup only happens once, whereas the drawing
+	 * happens many times, so this might be the best way to go.
+	 *
+	 * An alternative might be to not set up this mask, and instead, at
+	 * drawing time, for each transparent pixel, set its color to the
+	 * color of the background behind that pixel. This is what I suspect
+	 * most of programs do. However, they don't have to deal with the
+	 * canvas, which could have many different background colors.
+	 * Determining the correct bg color for a given pixel might be
+	 * expensive.
+	 */
+
+	if (compRule != TK_PHOTO_COMPOSITE_OVERLAY) {
+	    TkRegion workRgn;
+
+	    /*
+	     * Don't need this when using the OVERLAY compositing rule, which
+	     * always strictly increases the valid region.
+	     */
+
+	recalculateValidRegion:
+	    workRgn = TkCreateRegion();
+	    rect.x = x;
+	    rect.y = y;
+	    rect.width = width;
+	    rect.height = height;
+	    TkUnionRectWithRegion(&rect, workRgn, workRgn);
+	    TkSubtractRegion(masterPtr->validRegion, workRgn,
+		    masterPtr->validRegion);
+	    TkDestroyRegion(workRgn);
+	}
+
+	/*
+	 * Factorize out the main part of the building of the region data to
+	 * allow for more efficient per-platform implementations. [Bug 919066]
+	 */
+
+	TkpBuildRegionFromAlphaData(masterPtr->validRegion, (unsigned) x,
+		(unsigned) y, (unsigned) width, (unsigned) height,
+		masterPtr->pix32 + (y * masterPtr->width + x) * 4 + 3,
+		4, (unsigned) masterPtr->width * 4);
+    } else {
+	rect.x = x;
+	rect.y = y;
+	rect.width = width;
+	rect.height = height;
+	TkUnionRectWithRegion(&rect, masterPtr->validRegion,
+		masterPtr->validRegion);
+    }
+
+    /*
+     * Check if display code needs alpha blending...
+     */
+
+    if (!sourceIsSimplePhoto && (height == 1)) {
+	/*
+	 * Optimize the single span case if we can. This speeds up code that
+	 * builds up large simple-alpha images by scan-lines or individual
+	 * pixels. We don't negate COMPLEX_ALPHA in this case. [Bug 1409140]
+	 * [Patch 1539990]
+	 */
+
+	if (!(masterPtr->flags & COMPLEX_ALPHA)) {
+	    register int x1;
+
+	    for (x1=x ; x1<x+width ; x1++) {
+		register unsigned char newAlpha;
+
+		destLinePtr = masterPtr->pix32 + (y*masterPtr->width + x1)*4;
+		newAlpha = destLinePtr[3];
+		if (newAlpha && newAlpha != 255) {
+		    masterPtr->flags |= COMPLEX_ALPHA;
+		    break;
+		}
+	    }
+	}
+    } else if ((alphaOffset != 0) || (masterPtr->flags & COMPLEX_ALPHA)) {
+	/*
+	 * Check for partial transparency if alpha pixels are specified, or
+	 * rescan if we already knew such pixels existed. To restrict this
+	 * Toggle to only checking the changed pixels requires knowing where
+	 * the alpha pixels are.
+	 */
+
+	ToggleComplexAlphaIfNeeded(masterPtr);
+    }
+
+    /*
+     * Update each instance.
+     */
+
+    Tk_DitherPhoto((Tk_PhotoHandle)masterPtr, x, y, width, height);
+
+    /*
+     * Tell the core image code that this image has changed.
+     */
+
+    Tk_ImageChanged(masterPtr->tkMaster, x, y, width, height,
+	    masterPtr->width, masterPtr->height);
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoPutZoomedBlock --
+ *
+ *	This function is called to put image data into a photo image, with
+ *	possible subsampling and/or zooming of the pixels.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The image data is stored. The image may be expanded. The Tk image code
+ *	is informed that the image has changed.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+Tk_PhotoPutZoomedBlock(
+    Tcl_Interp *interp,		/* Interpreter for passing back error
+				 * messages, or NULL. */
+    Tk_PhotoHandle handle,	/* Opaque handle for the photo image to be
+				 * updated. */
+    register Tk_PhotoImageBlock *blockPtr,
+				/* Pointer to a structure describing the pixel
+				 * data to be copied into the image. */
+    int x, int y,		/* Coordinates of the top-left pixel to be
+				 * updated in the image. */
+    int width, int height,	/* Dimensions of the area of the image to be
+				 * updated. */
+    int zoomX, int zoomY,	/* Zoom factors for the X and Y axes. */
+    int subsampleX, int subsampleY,
+				/* Subsampling factors for the X and Y
+				 * axes. */
+    int compRule)		/* Compositing rule to use when processing
+				 * transparent pixels. */
+{
+    register PhotoMaster *masterPtr = (PhotoMaster *) handle;
+    int xEnd, yEnd, greenOffset, blueOffset, alphaOffset;
+    int wLeft, hLeft, wCopy, hCopy, blockWid, blockHt;
+    unsigned char *srcPtr, *srcLinePtr, *srcOrigPtr, *destPtr, *destLinePtr;
+    int pitch, xRepeat, yRepeat, blockXSkip, blockYSkip, sourceIsSimplePhoto;
+    XRectangle rect;
+
+    /*
+     * Zero-sized blocks never cause any changes. [Bug 3078902]
+     */
+
+    if (blockPtr->height == 0 || blockPtr->width == 0) {
+	return TCL_OK;
+    }
+
+    if (zoomX==1 && zoomY==1 && subsampleX==1 && subsampleY==1) {
+	return Tk_PhotoPutBlock(interp, handle, blockPtr, x, y, width, height,
+		compRule);
+    }
+
+    sourceIsSimplePhoto = compRule & SOURCE_IS_SIMPLE_ALPHA_PHOTO;
+    compRule &= ~SOURCE_IS_SIMPLE_ALPHA_PHOTO;
+
+    if (zoomX <= 0 || zoomY <= 0) {
+	return TCL_OK;
+    }
+    if ((masterPtr->userWidth != 0) && ((x + width) > masterPtr->userWidth)) {
+	width = masterPtr->userWidth - x;
+    }
+    if ((masterPtr->userHeight != 0)
+	    && ((y + height) > masterPtr->userHeight)) {
+	height = masterPtr->userHeight - y;
+    }
+    if (width <= 0 || height <= 0) {
+	return TCL_OK;
+    }
+
+    xEnd = x + width;
+    yEnd = y + height;
+    if ((xEnd > masterPtr->width) || (yEnd > masterPtr->height)) {
+	int sameSrc = (blockPtr->pixelPtr == masterPtr->pix32);
+
+	if (ImgPhotoSetSize(masterPtr, MAX(xEnd, masterPtr->width),
+		MAX(yEnd, masterPtr->height)) == TCL_ERROR) {
+	    if (interp != NULL) {
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+		Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	    }
+	    return TCL_ERROR;
+	}
+	if (sameSrc) {
+	    blockPtr->pixelPtr = masterPtr->pix32;
+	    blockPtr->pitch = masterPtr->width * 4;
+	}
+    }
+
+    if ((y < masterPtr->ditherY) || ((y == masterPtr->ditherY)
+	    && (x < masterPtr->ditherX))) {
+	/*
+	 * The dithering isn't correct past the start of this block.
+	 */
+
+	masterPtr->ditherX = x;
+	masterPtr->ditherY = y;
+    }
+
+    /*
+     * If this image block could have different red, green and blue
+     * components, mark it as a color image.
+     */
+
+    greenOffset = blockPtr->offset[1] - blockPtr->offset[0];
+    blueOffset = blockPtr->offset[2] - blockPtr->offset[0];
+    alphaOffset = blockPtr->offset[3];
+    if ((alphaOffset >= blockPtr->pixelSize) || (alphaOffset < 0)) {
+	alphaOffset = 0;
+	sourceIsSimplePhoto = 1;
+    } else {
+	alphaOffset -= blockPtr->offset[0];
+    }
+    if ((greenOffset != 0) || (blueOffset != 0)) {
+	masterPtr->flags |= COLOR_IMAGE;
+    }
+
+    /*
+     * Work out what area the pixel data in the block expands to after
+     * subsampling and zooming.
+     */
+
+    blockXSkip = subsampleX * blockPtr->pixelSize;
+    blockYSkip = subsampleY * blockPtr->pitch;
+    if (subsampleX > 0) {
+	blockWid = ((blockPtr->width + subsampleX - 1) / subsampleX) * zoomX;
+    } else if (subsampleX == 0) {
+	blockWid = width;
+    } else {
+	blockWid = ((blockPtr->width - subsampleX - 1) / -subsampleX) * zoomX;
+    }
+    if (subsampleY > 0) {
+	blockHt = ((blockPtr->height + subsampleY - 1) / subsampleY) * zoomY;
+    } else if (subsampleY == 0) {
+	blockHt = height;
+    } else {
+	blockHt = ((blockPtr->height - subsampleY - 1) / -subsampleY) * zoomY;
+    }
+
+    /*
+     * Copy the data into our local 32-bit/pixel array.
+     */
+
+    destLinePtr = masterPtr->pix32 + (y * masterPtr->width + x) * 4;
+    srcOrigPtr = blockPtr->pixelPtr + blockPtr->offset[0];
+    if (subsampleX < 0) {
+	srcOrigPtr += (blockPtr->width - 1) * blockPtr->pixelSize;
+    }
+    if (subsampleY < 0) {
+	srcOrigPtr += (blockPtr->height - 1) * blockPtr->pitch;
+    }
+
+    pitch = masterPtr->width * 4;
+    for (hLeft = height; hLeft > 0; ) {
+	hCopy = MIN(hLeft, blockHt);
+	hLeft -= hCopy;
+	yRepeat = zoomY;
+	srcLinePtr = srcOrigPtr;
+	for (; hCopy > 0; --hCopy) {
+	    destPtr = destLinePtr;
+	    for (wLeft = width; wLeft > 0;) {
+		wCopy = MIN(wLeft, blockWid);
+		wLeft -= wCopy;
+		srcPtr = srcLinePtr;
+		for (; wCopy > 0; wCopy -= zoomX) {
+		    for (xRepeat = MIN(wCopy, zoomX); xRepeat > 0; xRepeat--) {
+			int alpha = srcPtr[alphaOffset];/* Source alpha. */
+
+			/*
+			 * Common case (solid pixels) first
+			 */
+
+			if (!alphaOffset || (alpha == 255)) {
+			    *destPtr++ = srcPtr[0];
+			    *destPtr++ = srcPtr[greenOffset];
+			    *destPtr++ = srcPtr[blueOffset];
+			    *destPtr++ = 255;
+			    continue;
+ 			}
+
+			if (compRule==TK_PHOTO_COMPOSITE_SET || !destPtr[3]) {
+			    /*
+			     * Either this is the SET rule (we overwrite
+			     * whatever is there) or the destination is
+			     * entirely blank. In both cases, we just set the
+			     * destination to the source.
+			     */
+
+			    *destPtr++ = srcPtr[0];
+			    *destPtr++ = srcPtr[greenOffset];
+			    *destPtr++ = srcPtr[blueOffset];
+			    *destPtr++ = alpha;
+			} else if (alpha) {
+			    int Alpha = destPtr[3];	/* Destination
+							 * alpha. */
+
+			    destPtr[0] = PD_SRC_OVER(srcPtr[0], alpha,
+				    destPtr[0], Alpha);
+			    destPtr[1] = PD_SRC_OVER(srcPtr[greenOffset],alpha,
+				    destPtr[1], Alpha);
+			    destPtr[2] = PD_SRC_OVER(srcPtr[blueOffset], alpha,
+				    destPtr[2], Alpha);
+			    destPtr[3] = PD_SRC_OVER_ALPHA(alpha, Alpha);
+
+			    destPtr += 4;
+			} else {
+			    destPtr += 4;
+			}
+		    }
+		    srcPtr += blockXSkip;
+		}
+	    }
+	    destLinePtr += pitch;
+	    yRepeat--;
+	    if (yRepeat <= 0) {
+		srcLinePtr += blockYSkip;
+		yRepeat = zoomY;
+	    }
+	}
+    }
+
+    /*
+     * Recompute the region of data for which we have valid pixels to plot.
+     */
+
+    if (alphaOffset) {
+	if (compRule != TK_PHOTO_COMPOSITE_OVERLAY) {
+	    /*
+	     * Don't need this when using the OVERLAY compositing rule, which
+	     * always strictly increases the valid region.
+	     */
+
+	    TkRegion workRgn = TkCreateRegion();
+
+	    rect.x = x;
+	    rect.y = y;
+	    rect.width = width;
+	    rect.height = 1;
+	    TkUnionRectWithRegion(&rect, workRgn, workRgn);
+	    TkSubtractRegion(masterPtr->validRegion, workRgn,
+		    masterPtr->validRegion);
+	    TkDestroyRegion(workRgn);
+	}
+
+	TkpBuildRegionFromAlphaData(masterPtr->validRegion,
+		(unsigned)x, (unsigned)y, (unsigned)width, (unsigned)height,
+		&masterPtr->pix32[(y * masterPtr->width + x) * 4 + 3], 4,
+		(unsigned) masterPtr->width * 4);
+    } else {
+	rect.x = x;
+	rect.y = y;
+	rect.width = width;
+	rect.height = height;
+	TkUnionRectWithRegion(&rect, masterPtr->validRegion,
+		masterPtr->validRegion);
+    }
+
+    /*
+     * Check if display code needs alpha blending...
+     */
+
+    if (!sourceIsSimplePhoto && (width == 1) && (height == 1)) {
+	/*
+	 * Optimize the single pixel case if we can. This speeds up code that
+	 * builds up large simple-alpha images by single pixels. We don't
+	 * negate COMPLEX_ALPHA in this case. [Bug 1409140]
+	 */
+	if (!(masterPtr->flags & COMPLEX_ALPHA)) {
+	    unsigned char newAlpha;
+
+	    destLinePtr = masterPtr->pix32 + (y * masterPtr->width + x) * 4;
+	    newAlpha = destLinePtr[3];
+
+	    if (newAlpha && newAlpha != 255) {
+		masterPtr->flags |= COMPLEX_ALPHA;
+	    }
+	}
+    } else if ((alphaOffset != 0) || (masterPtr->flags & COMPLEX_ALPHA)) {
+	/*
+	 * Check for partial transparency if alpha pixels are specified, or
+	 * rescan if we already knew such pixels existed. To restrict this
+	 * Toggle to only checking the changed pixels requires knowing where
+	 * the alpha pixels are.
+	 */
+	ToggleComplexAlphaIfNeeded(masterPtr);
+    }
+
+    /*
+     * Update each instance.
+     */
+
+    Tk_DitherPhoto((Tk_PhotoHandle) masterPtr, x, y, width, height);
+
+    /*
+     * Tell the core image code that this image has changed.
+     */
+
+    Tk_ImageChanged(masterPtr->tkMaster, x, y, width, height, masterPtr->width,
+	    masterPtr->height);
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_DitherPhoto --
+ *
+ *	This function is called to update an area of each instance's pixmap by
+ *	dithering the corresponding area of the image master.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The pixmap of each instance of this image gets updated. The fields in
+ *	*masterPtr indicating which area of the image is correctly dithered
+ *	get updated.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+Tk_DitherPhoto(
+    Tk_PhotoHandle photo,	/* Image master whose instances are to be
+				 * updated. */
+    int x, int y,		/* Coordinates of the top-left pixel in the
+				 * area to be dithered. */
+    int width, int height)	/* Dimensions of the area to be dithered. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) photo;
+    PhotoInstance *instancePtr;
+
+    if ((width <= 0) || (height <= 0)) {
+	return;
+    }
+
+    for (instancePtr = masterPtr->instancePtr; instancePtr != NULL;
+	    instancePtr = instancePtr->nextPtr) {
+	TkImgDitherInstance(instancePtr, x, y, width, height);
+    }
+
+    /*
+     * Work out whether this block will be correctly dithered and whether it
+     * will extend the correctly dithered region.
+     */
+
+    if (((y < masterPtr->ditherY)
+	    || ((y == masterPtr->ditherY) && (x <= masterPtr->ditherX)))
+	    && ((y + height) > (masterPtr->ditherY))) {
+	/*
+	 * This block starts inside (or immediately after) the correctly
+	 * dithered region, so the first scan line at least will be right.
+	 * Furthermore this block extends into scanline masterPtr->ditherY.
+	 */
+
+	if ((x == 0) && (width == masterPtr->width)) {
+	    /*
+	     * We are doing the full width, therefore the dithering will be
+	     * correct to the end.
+	     */
+
+	    masterPtr->ditherX = 0;
+	    masterPtr->ditherY = y + height;
+	} else {
+	    /*
+	     * We are doing partial scanlines, therefore the
+	     * correctly-dithered region will be extended by at most one scan
+	     * line.
+	     */
+
+	    if (x <= masterPtr->ditherX) {
+		masterPtr->ditherX = x + width;
+		if (masterPtr->ditherX >= masterPtr->width) {
+		    masterPtr->ditherX = 0;
+		    masterPtr->ditherY++;
+		}
+	    }
+	}
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoBlank --
+ *
+ *	This function is called to clear an entire photo image.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The valid region for the image is set to the null region. The generic
+ *	image code is notified that the image has changed.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+Tk_PhotoBlank(
+    Tk_PhotoHandle handle)	/* Handle for the image to be blanked. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) handle;
+    PhotoInstance *instancePtr;
+
+    masterPtr->ditherX = masterPtr->ditherY = 0;
+    masterPtr->flags = 0;
+
+    /*
+     * The image has valid data nowhere.
+     */
+
+    if (masterPtr->validRegion != NULL) {
+	TkDestroyRegion(masterPtr->validRegion);
+    }
+    masterPtr->validRegion = TkCreateRegion();
+
+    /*
+     * Clear out the 32-bit pixel storage array. Clear out the dithering error
+     * arrays for each instance.
+     */
+
+    memset(masterPtr->pix32, 0,
+	    ((size_t)masterPtr->width * masterPtr->height * 4));
+    for (instancePtr = masterPtr->instancePtr; instancePtr != NULL;
+	    instancePtr = instancePtr->nextPtr) {
+	TkImgResetDither(instancePtr);
+    }
+
+    /*
+     * Tell the core image code that this image has changed.
+     */
+
+    Tk_ImageChanged(masterPtr->tkMaster, 0, 0, masterPtr->width,
+	    masterPtr->height, masterPtr->width, masterPtr->height);
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoExpand --
+ *
+ *	This function is called to request that a photo image be expanded if
+ *	necessary to be at least `width' pixels wide and `height' pixels high.
+ *	If the user has declared a definite image size (using the -width and
+ *	-height configuration options) then this call has no effect.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The size of the photo image may change; if so the generic image code
+ *	is informed.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+Tk_PhotoExpand(
+    Tcl_Interp *interp,		/* Interpreter for passing back error
+				 * messages, or NULL. */
+    Tk_PhotoHandle handle,	/* Handle for the image to be expanded. */
+    int width, int height)	/* Desired minimum dimensions of the image. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) handle;
+
+    if (width <= masterPtr->width) {
+	width = masterPtr->width;
+    }
+    if (height <= masterPtr->height) {
+	height = masterPtr->height;
+    }
+    if ((width != masterPtr->width) || (height != masterPtr->height)) {
+	if (ImgPhotoSetSize(masterPtr, MAX(width, masterPtr->width),
+		MAX(height, masterPtr->height)) == TCL_ERROR) {
+	    if (interp != NULL) {
+		Tcl_SetObjResult(interp, Tcl_NewStringObj(
+			TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+		Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	    }
+	    return TCL_ERROR;
+	}
+	Tk_ImageChanged(masterPtr->tkMaster, 0, 0, 0, 0, masterPtr->width,
+		masterPtr->height);
+    }
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoGetSize --
+ *
+ *	This function is called to obtain the current size of a photo image.
+ *
+ * Results:
+ *	The image's width and height are returned in *widthp and *heightp.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+Tk_PhotoGetSize(
+    Tk_PhotoHandle handle,	/* Handle for the image whose dimensions are
+				 * requested. */
+    int *widthPtr, int *heightPtr)
+				/* The dimensions of the image are returned
+				 * here. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) handle;
+
+    *widthPtr = masterPtr->width;
+    *heightPtr = masterPtr->height;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoSetSize --
+ *
+ *	This function is called to set size of a photo image. This call is
+ *	equivalent to using the -width and -height configuration options.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	The size of the image may change; if so the generic image code is
+ *	informed.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+Tk_PhotoSetSize(
+    Tcl_Interp *interp,		/* Interpreter for passing back error
+				 * messages, or NULL. */
+    Tk_PhotoHandle handle,	/* Handle for the image whose size is to be
+				 * set. */
+    int width, int height)	/* New dimensions for the image. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) handle;
+
+    masterPtr->userWidth = width;
+    masterPtr->userHeight = height;
+    if (ImgPhotoSetSize(masterPtr, ((width > 0) ? width: masterPtr->width),
+	    ((height > 0) ? height: masterPtr->height)) == TCL_ERROR) {
+	if (interp != NULL) {
+	    Tcl_SetObjResult(interp, Tcl_NewStringObj(
+		    TK_PHOTO_ALLOC_FAILURE_MESSAGE, -1));
+	    Tcl_SetErrorCode(interp, "TK", "MALLOC", NULL);
+	}
+	return TCL_ERROR;
+    }
+    Tk_ImageChanged(masterPtr->tkMaster, 0, 0, 0, 0,
+	    masterPtr->width, masterPtr->height);
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TkGetPhotoValidRegion --
+ *
+ *	This function is called to get the part of the photo where there is
+ *	valid data. Or, conversely, the part of the photo which is
+ *	transparent.
+ *
+ * Results:
+ *	A TkRegion value that indicates the current area of the photo that is
+ *	valid. This value should not be used after any modification to the
+ *	photo image.
+ *
+ * Side Effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+TkRegion
+TkPhotoGetValidRegion(
+    Tk_PhotoHandle handle)	/* Handle for the image whose valid region is
+				 * to obtained. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) handle;
+
+    return masterPtr->validRegion;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgGetPhoto --
+ *
+ *	This function is called to obtain image data from a photo image. This
+ *	function fills in the Tk_PhotoImageBlock structure pointed to by
+ *	`blockPtr' with details of the address and layout of the image data in
+ *	memory.
+ *
+ * Results:
+ *	A pointer to the allocated data which should be freed later. NULL if
+ *	there is no need to free data because blockPtr->pixelPtr points
+ *	directly to the image data.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static char *
+ImgGetPhoto(
+    PhotoMaster *masterPtr,	/* Handle for the photo image from which image
+				 * data is desired. */
+    Tk_PhotoImageBlock *blockPtr,
+				/* Information about the address and layout of
+				 * the image data is returned here. */
+    struct SubcommandOptions *optPtr)
+{
+    unsigned char *pixelPtr;
+    int x, y, greenOffset, blueOffset, alphaOffset;
+
+    Tk_PhotoGetImage((Tk_PhotoHandle) masterPtr, blockPtr);
+    blockPtr->pixelPtr += optPtr->fromY * blockPtr->pitch
+	    + optPtr->fromX * blockPtr->pixelSize;
+    blockPtr->width = optPtr->fromX2 - optPtr->fromX;
+    blockPtr->height = optPtr->fromY2 - optPtr->fromY;
+
+    if (!(masterPtr->flags & COLOR_IMAGE) &&
+	    (!(optPtr->options & OPT_BACKGROUND)
+	    || ((optPtr->background->red == optPtr->background->green)
+	    && (optPtr->background->red == optPtr->background->blue)))) {
+	blockPtr->offset[0] = blockPtr->offset[1] = blockPtr->offset[2];
+    }
+    alphaOffset = 0;
+    for (y = 0; y < blockPtr->height; y++) {
+	pixelPtr = blockPtr->pixelPtr + (y * blockPtr->pitch)
+		+ blockPtr->pixelSize - 1;
+	for (x = 0; x < blockPtr->width; x++) {
+	    if (*pixelPtr != 255) {
+		alphaOffset = 3;
+		break;
+	    }
+	    pixelPtr += blockPtr->pixelSize;
+	}
+	if (alphaOffset) {
+	    break;
+	}
+    }
+    if (!alphaOffset) {
+	blockPtr->offset[3]= -1; /* Tell caller alpha need not be read */
+    }
+    greenOffset = blockPtr->offset[1] - blockPtr->offset[0];
+    blueOffset = blockPtr->offset[2] - blockPtr->offset[0];
+    if (((optPtr->options & OPT_BACKGROUND) && alphaOffset) ||
+	    ((optPtr->options & OPT_GRAYSCALE) && (greenOffset||blueOffset))) {
+	int newPixelSize,x,y;
+	unsigned char *srcPtr, *destPtr;
+	char *data;
+
+	newPixelSize = (!(optPtr->options & OPT_BACKGROUND) && alphaOffset)
+		? 2 : 1;
+	if ((greenOffset||blueOffset) && !(optPtr->options & OPT_GRAYSCALE)) {
+	    newPixelSize += 2;
+	}
+
+	if (blockPtr->height > (int)((UINT_MAX/newPixelSize)/blockPtr->width)) {
+	    return NULL;
+	}
+	data = attemptckalloc(newPixelSize*blockPtr->width*blockPtr->height);
+	if (data == NULL) {
+	    return NULL;
+	}
+	srcPtr = blockPtr->pixelPtr + blockPtr->offset[0];
+	destPtr = (unsigned char *) data;
+	if (!greenOffset && !blueOffset) {
+	    for (y = blockPtr->height; y > 0; y--) {
+		for (x = blockPtr->width; x > 0; x--) {
+		    *destPtr = *srcPtr;
+		    srcPtr += blockPtr->pixelSize;
+		    destPtr += newPixelSize;
+		}
+		srcPtr += blockPtr->pitch -
+			blockPtr->width * blockPtr->pixelSize;
+	    }
+	} else if (optPtr->options & OPT_GRAYSCALE) {
+	    for (y = blockPtr->height; y > 0; y--) {
+		for (x = blockPtr->width; x > 0; x--) {
+		    *destPtr = (unsigned char) ((srcPtr[0]*11 + srcPtr[1]*16
+			    + srcPtr[2]*5 + 16) >> 5);
+		    srcPtr += blockPtr->pixelSize;
+		    destPtr += newPixelSize;
+		}
+		srcPtr += blockPtr->pitch -
+			blockPtr->width * blockPtr->pixelSize;
+	    }
+	} else {
+	    for (y = blockPtr->height; y > 0; y--) {
+		for (x = blockPtr->width; x > 0; x--) {
+		    destPtr[0] = srcPtr[0];
+		    destPtr[1] = srcPtr[1];
+		    destPtr[2] = srcPtr[2];
+		    srcPtr += blockPtr->pixelSize;
+		    destPtr += newPixelSize;
+		}
+		srcPtr += blockPtr->pitch -
+			blockPtr->width * blockPtr->pixelSize;
+	    }
+	}
+	srcPtr = blockPtr->pixelPtr + alphaOffset;
+	destPtr = (unsigned char *) data;
+	if (!alphaOffset) {
+	    /*
+	     * Nothing to be done.
+	     */
+	} else if (optPtr->options & OPT_BACKGROUND) {
+	    if (newPixelSize > 2) {
+		int red = optPtr->background->red>>8;
+		int green = optPtr->background->green>>8;
+		int blue = optPtr->background->blue>>8;
+
+		for (y = blockPtr->height; y > 0; y--) {
+		    for (x = blockPtr->width; x > 0; x--) {
+			destPtr[0] += (unsigned char) (((255 - *srcPtr) *
+				(red-destPtr[0])) / 255);
+			destPtr[1] += (unsigned char) (((255 - *srcPtr) *
+				(green-destPtr[1])) / 255);
+			destPtr[2] += (unsigned char) (((255 - *srcPtr) *
+				(blue-destPtr[2])) / 255);
+			srcPtr += blockPtr->pixelSize;
+			destPtr += newPixelSize;
+		    }
+		    srcPtr += blockPtr->pitch -
+			    blockPtr->width * blockPtr->pixelSize;
+		}
+	    } else {
+	 	int gray = (unsigned char) (((optPtr->background->red>>8) * 11
+			+ (optPtr->background->green>>8) * 16
+			+ (optPtr->background->blue>>8) * 5 + 16) >> 5);
+
+		for (y = blockPtr->height; y > 0; y--) {
+		    for (x = blockPtr->width; x > 0; x--) {
+			destPtr[0] += ((255 - *srcPtr) *
+				(gray-destPtr[0])) / 255;
+			srcPtr += blockPtr->pixelSize;
+			destPtr += newPixelSize;
+		    }
+		    srcPtr += blockPtr->pitch -
+			    blockPtr->width * blockPtr->pixelSize;
+		}
+	    }
+	} else {
+	    destPtr += newPixelSize-1;
+	    for (y = blockPtr->height; y > 0; y--) {
+		for (x = blockPtr->width; x > 0; x--) {
+		    *destPtr = *srcPtr;
+		    srcPtr += blockPtr->pixelSize;
+		    destPtr += newPixelSize;
+		}
+		srcPtr += blockPtr->pitch -
+			blockPtr->width * blockPtr->pixelSize;
+	    }
+	}
+	blockPtr->pixelPtr = (unsigned char *) data;
+	blockPtr->pixelSize = newPixelSize;
+	blockPtr->pitch = newPixelSize * blockPtr->width;
+	blockPtr->offset[0] = 0;
+	if (newPixelSize > 2) {
+	    blockPtr->offset[1] = 1;
+	    blockPtr->offset[2] = 2;
+	    blockPtr->offset[3]= 3;
+	} else {
+	    blockPtr->offset[1] = 0;
+	    blockPtr->offset[2] = 0;
+	    blockPtr->offset[3]= 1;
+	}
+	return data;
+    }
+    return NULL;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * ImgStringWrite --
+ *
+ *	Default string write function. The data is formatted in the default
+ *	format as accepted by the "<img> put" command.
+ *
+ * Results:
+ *	A standard Tcl result.
+ *
+ * Side effects:
+ *	See the user documentation.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+ImgStringWrite(
+    Tcl_Interp *interp,
+    Tcl_Obj *formatString,
+    Tk_PhotoImageBlock *blockPtr)
+{
+    int greenOffset, blueOffset;
+    Tcl_Obj *data;
+
+    greenOffset = blockPtr->offset[1] - blockPtr->offset[0];
+    blueOffset = blockPtr->offset[2] - blockPtr->offset[0];
+
+    data = Tcl_NewObj();
+    if ((blockPtr->width > 0) && (blockPtr->height > 0)) {
+	int row, col;
+
+	for (row=0; row<blockPtr->height; row++) {
+	    Tcl_Obj *line = Tcl_NewObj();
+	    unsigned char *pixelPtr = blockPtr->pixelPtr + blockPtr->offset[0]
+		    + row * blockPtr->pitch;
+
+	    for (col=0; col<blockPtr->width; col++) {
+		Tcl_AppendPrintfToObj(line, "%s#%02x%02x%02x",
+			col ? " " : "", *pixelPtr,
+			pixelPtr[greenOffset], pixelPtr[blueOffset]);
+		pixelPtr += blockPtr->pixelSize;
+	    }
+	    Tcl_ListObjAppendElement(NULL, data, line);
+	}
+    }
+    Tcl_SetObjResult(interp, data);
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoGetImage --
+ *
+ *	This function is called to obtain image data from a photo image. This
+ *	function fills in the Tk_PhotoImageBlock structure pointed to by
+ *	`blockPtr' with details of the address and layout of the image data in
+ *	memory.
+ *
+ * Results:
+ *	TRUE (1) indicating that image data is available, for backwards
+ *	compatibility with the old photo widget.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+Tk_PhotoGetImage(
+    Tk_PhotoHandle handle,	/* Handle for the photo image from which image
+				 * data is desired. */
+    Tk_PhotoImageBlock *blockPtr)
+				/* Information about the address and layout of
+				 * the image data is returned here. */
+{
+    PhotoMaster *masterPtr = (PhotoMaster *) handle;
+
+    blockPtr->pixelPtr = masterPtr->pix32;
+    blockPtr->width = masterPtr->width;
+    blockPtr->height = masterPtr->height;
+    blockPtr->pitch = masterPtr->width * 4;
+    blockPtr->pixelSize = 4;
+    blockPtr->offset[0] = 0;
+    blockPtr->offset[1] = 1;
+    blockPtr->offset[2] = 2;
+    blockPtr->offset[3] = 3;
+    return 1;
+}
+
+/*
+ *--------------------------------------------------------------
+ *
+ * TkPostscriptPhoto --
+ *
+ *	This function is called to output the contents of a photo image in
+ *	Postscript by calling the Tk_PostscriptPhoto function.
+ *
+ * Results:
+ *	Returns a standard Tcl return value.
+ *
+ * Side effects:
+ *	None.
+ *
+ *--------------------------------------------------------------
+ */
+
+static int
+ImgPhotoPostscript(
+    ClientData clientData,	/* Handle for the photo image. */
+    Tcl_Interp *interp,		/* Interpreter. */
+    Tk_Window tkwin,		/* (unused) */
+    Tk_PostscriptInfo psInfo,	/* Postscript info. */
+    int x, int y,		/* First pixel to output. */
+    int width, int height,	/* Width and height of area. */
+    int prepass)		/* (unused) */
+{
+    Tk_PhotoImageBlock block;
+
+    Tk_PhotoGetImage(clientData, &block);
+    block.pixelPtr += y * block.pitch + x * block.pixelSize;
+
+    return Tk_PostscriptPhoto(interp, &block, psInfo, width, height);
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoPutBlock_NoComposite, Tk_PhotoPutZoomedBlock_NoComposite --
+ *
+ * These backward-compatability functions just exist to fill slots in stubs
+ * table. For the behaviour of *_NoComposite, refer to the corresponding
+ * function without the extra suffix, except that the compositing rule is
+ * always "overlay" and the function always panics on memory-allocation
+ * failure.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+Tk_PhotoPutBlock_NoComposite(
+    Tk_PhotoHandle handle,
+    Tk_PhotoImageBlock *blockPtr,
+    int x, int y, int width, int height)
+{
+    if (Tk_PhotoPutBlock(NULL, handle, blockPtr, x, y, width, height,
+	    TK_PHOTO_COMPOSITE_OVERLAY) != TCL_OK) {
+	Tcl_Panic(TK_PHOTO_ALLOC_FAILURE_MESSAGE);
+    }
+}
+
+void
+Tk_PhotoPutZoomedBlock_NoComposite(
+    Tk_PhotoHandle handle,
+    Tk_PhotoImageBlock *blockPtr,
+    int x, int y, int width, int height,
+    int zoomX, int zoomY, int subsampleX, int subsampleY)
+{
+    if (Tk_PhotoPutZoomedBlock(NULL, handle, blockPtr, x, y, width, height,
+	    zoomX, zoomY, subsampleX, subsampleY,
+	    TK_PHOTO_COMPOSITE_OVERLAY) != TCL_OK) {
+	Tcl_Panic(TK_PHOTO_ALLOC_FAILURE_MESSAGE);
+    }
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * Tk_PhotoExpand_Panic, Tk_PhotoPutBlock_Panic,
+ * Tk_PhotoPutZoomedBlock_Panic, Tk_PhotoSetSize_Panic
+ *
+ * Backward compatability functions for preserving the old behaviour (i.e.
+ * panic on memory allocation failure) so that extensions do not need to be
+ * significantly updated to take account of TIP #116. These call the new
+ * interface (i.e. the interface without the extra suffix), but panic if an
+ * error condition is returned.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+Tk_PhotoExpand_Panic(
+    Tk_PhotoHandle handle,
+    int width, int height)
+{
+    if (Tk_PhotoExpand(NULL, handle, width, height) != TCL_OK) {
+	Tcl_Panic(TK_PHOTO_ALLOC_FAILURE_MESSAGE);
+    }
+}
+
+void
+Tk_PhotoPutBlock_Panic(
+    Tk_PhotoHandle handle,
+    Tk_PhotoImageBlock *blockPtr,
+    int x, int y, int width, int height, int compRule)
+{
+    if (Tk_PhotoPutBlock(NULL, handle, blockPtr, x, y, width, height,
+	    compRule) != TCL_OK) {
+	Tcl_Panic(TK_PHOTO_ALLOC_FAILURE_MESSAGE);
+    }
+}
+
+void
+Tk_PhotoPutZoomedBlock_Panic(
+    Tk_PhotoHandle handle, Tk_PhotoImageBlock *blockPtr,
+    int x, int y, int width, int height,
+    int zoomX, int zoomY, int subsampleX, int subsampleY,
+    int compRule)
+{
+    if (Tk_PhotoPutZoomedBlock(NULL, handle, blockPtr, x, y, width, height,
+	    zoomX, zoomY, subsampleX, subsampleY, compRule) != TCL_OK) {
+	Tcl_Panic(TK_PHOTO_ALLOC_FAILURE_MESSAGE);
+    }
+}
+
+void
+Tk_PhotoSetSize_Panic(
+    Tk_PhotoHandle handle,
+    int width, int height)
+{
+    if (Tk_PhotoSetSize(NULL, handle, width, height) != TCL_OK) {
+	Tcl_Panic(TK_PHOTO_ALLOC_FAILURE_MESSAGE);
+    }
+}
+
+/*
+ * Local Variables:
+ * mode: c
+ * c-basic-offset: 4
+ * fill-column: 78
+ * End:
+ */