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authorWilliam Joye <wjoye@cfa.harvard.edu>2019-07-31 17:58:33 (GMT)
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+'\"
+'\" Copyright (c) 1994 The Australian National University
+'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.
+'\"
+'\" 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.
+'\"
+.TH photo n 4.0 Tk "Tk Built-In Commands"
+.so man.macros
+.BS
+'\" Note: do not modify the .SH NAME line immediately below!
+.SH NAME
+photo \- Full-color images
+.SH SYNOPSIS
+.nf
+\fBimage create photo \fR?\fIname\fR? ?\fIoptions\fR?
+
+\fIimageName \fBblank\fR
+\fIimageName \fBcget \fIoption\fR
+\fIimageName \fBconfigure\fR ?\fIoption\fR? ?\fIvalue option value ...\fR?
+\fIimageName \fBcopy \fIsourceImage\fR ?\fIoption value(s) ...\fR?
+\fIimageName \fBdata\fR ?\fIoption value(s) ...\fR?
+\fIimageName \fBget \fIx y\fR
+\fIimageName \fBput \fIdata\fR ?\fIoption value(s) ...\fR?
+\fIimageName \fBread \fIfilename\fR ?\fIoption value(s) ...\fR?
+\fIimageName \fBredither\fR
+\fIimageName \fBtransparency \fIsubcommand \fR?\fIarg arg ...\fR?
+\fIimageName \fBwrite \fIfilename\fR ?\fIoption value(s) ...\fR?
+.fi
+.BE
+.SH DESCRIPTION
+.PP
+A photo is an image whose pixels can display any color or be
+transparent. A photo image is stored internally in full color (32
+bits per pixel), and is displayed using dithering if necessary. Image
+data for a photo image can be obtained from a file or a string, or it
+can be supplied from
+C code through a procedural interface. At present, only
+.VS 8.6
+PNG,
+.VE 8.6
+GIF and PPM/PGM
+formats are supported, but an interface exists to allow additional
+image file formats to be added easily. A photo image is transparent
+in regions where no image data has been supplied
+or where it has been set transparent by the \fBtransparency set\fR
+subcommand.
+.SH "CREATING PHOTOS"
+.PP
+Like all images, photos are created using the \fBimage create\fR
+command.
+Photos support the following \fIoptions\fR:
+.TP
+\fB\-data \fIstring\fR
+.
+Specifies the contents of the image as a string. The string should
+contain binary data or, for some formats, base64-encoded data (this is
+currently guaranteed to be supported for PNG and GIF images). The
+format of the
+string must be one of those for which there is an image file format
+handler that will accept string data. If both the \fB\-data\fR
+and \fB\-file\fR options are specified, the \fB\-file\fR option takes
+precedence.
+.TP
+\fB\-format \fIformat-name\fR
+.
+Specifies the name of the file format for the data specified with the
+\fB\-data\fR or \fB\-file\fR option.
+.TP
+\fB\-file \fIname\fR
+.
+\fIname\fR gives the name of a file that is to be read to supply data
+for the photo image. The file format must be one of those for which
+there is an image file format handler that can read data.
+.TP
+\fB\-gamma \fIvalue\fR
+.
+Specifies that the colors allocated for displaying this image in a
+window should be corrected for a non-linear display with the specified
+gamma exponent value. (The intensity produced by most
+CRT displays is a power function of the input value, to a good
+approximation; gamma is the exponent and is typically around 2).
+The value specified must be greater than zero. The default
+value is one (no correction). In general, values greater than one
+will make the image lighter, and values less than one will make it
+darker.
+.TP
+\fB\-height \fInumber\fR
+.
+Specifies the height of the image, in pixels. This option is useful
+primarily in situations where the user wishes to build up the contents
+of the image piece by piece. A value of zero (the default) allows the
+image to expand or shrink vertically to fit the data stored in it.
+.TP
+\fB\-palette \fIpalette-spec\fR
+.
+Specifies the resolution of the color cube to be allocated for
+displaying this image, and thus the number of colors used from the
+colormaps of the windows where it is displayed. The
+\fIpalette-spec\fR string may be either a single decimal number,
+specifying the number of shades of gray to use, or three decimal
+numbers separated by slashes (/), specifying the number of shades of
+red, green and blue to use, respectively. If the first form (a single
+number) is used, the image will be displayed in monochrome (i.e.,
+grayscale).
+.TP
+\fB\-width \fInumber\fR
+.
+Specifies the width of the image, in pixels. This option is useful
+primarily in situations where the user wishes to build up the contents
+of the image piece by piece. A value of zero (the default) allows the
+image to expand or shrink horizontally to fit the data stored in it.
+.SH "IMAGE COMMAND"
+.PP
+When a photo image is created, Tk also creates a new command
+whose name is the same as the image.
+This command may be used to invoke various operations
+on the image.
+It has the following general form:
+.CS
+\fIimageName option \fR?\fIarg arg ...\fR?
+.CE
+\fIOption\fR and the \fIarg\fRs
+determine the exact behavior of the command.
+.PP
+Those options that write data to the image generally expand the size
+of the image, if necessary, to accommodate the data written to the
+image, unless the user has specified non-zero values for the
+\fB\-width\fR and/or \fB\-height\fR configuration options, in which
+case the width and/or height, respectively, of the image will not be
+changed.
+.PP
+The following commands are possible for photo images:
+.TP
+\fIimageName \fBblank\fR
+.
+Blank the image; that is, set the entire image to have no data, so it
+will be displayed as transparent, and the background of whatever
+window it is displayed in will show through.
+.TP
+\fIimageName \fBcget\fR \fIoption\fR
+.
+Returns the current value of the configuration option given
+by \fIoption\fR.
+\fIOption\fR may have any of the values accepted by the
+\fBimage create\fR \fBphoto\fR command.
+.TP
+\fIimageName \fBconfigure\fR ?\fIoption\fR? ?\fIvalue option value ...\fR?
+.
+Query or modify the configuration options for the image.
+If no \fIoption\fR is specified, returns a list describing all of
+the available options for \fIimageName\fR (see \fBTk_ConfigureInfo\fR for
+information on the format of this list). If \fIoption\fR is specified
+with no \fIvalue\fR, then the command returns a list describing the
+one named option (this list will be identical to the corresponding
+sublist of the value returned if no \fIoption\fR is specified). If
+one or more \fIoption\-value\fR pairs are specified, then the command
+modifies the given option(s) to have the given value(s); in
+this case the command returns an empty string.
+\fIOption\fR may have any of the values accepted by the
+\fBimage create\fR \fBphoto\fR command.
+.TP
+\fIimageName \fBcopy\fR \fIsourceImage\fR ?\fIoption value(s) ...\fR?
+.
+Copies a region from the image called \fIsourceImage\fR (which must
+be a photo image) to the image called \fIimageName\fR, possibly with
+pixel zooming and/or subsampling. If no options are specified, this
+command copies the whole of \fIsourceImage\fR into \fIimageName\fR,
+starting at coordinates (0,0) in \fIimageName\fR. The following
+options may be specified:
+.RS
+.TP
+\fB\-from \fIx1 y1 x2 y2\fR
+.
+Specifies a rectangular sub-region of the source image to be copied.
+(\fIx1,y1\fR) and (\fIx2,y2\fR) specify diagonally opposite corners of
+the rectangle. If \fIx2\fR and \fIy2\fR are not specified, the
+default value is the bottom-right corner of the source image. The
+pixels copied will include the left and top edges of the specified
+rectangle but not the bottom or right edges. If the \fB\-from\fR
+option is not given, the default is the whole source image.
+.TP
+\fB\-to \fIx1 y1 x2 y2\fR
+.
+Specifies a rectangular sub-region of the destination image to be
+affected. (\fIx1,y1\fR) and (\fIx2,y2\fR) specify diagonally opposite
+corners of the rectangle. If \fIx2\fR and \fIy2\fR are not specified,
+the default value is (\fIx1,y1\fR) plus the size of the source
+region (after subsampling and zooming, if specified). If \fIx2\fR and
+\fIy2\fR are specified, the source region will be replicated if
+necessary to fill the destination region in a tiled fashion.
+.TP
+\fB\-shrink\fR
+.
+Specifies that the size of the destination image should be reduced, if
+necessary, so that the region being copied into is at the bottom-right
+corner of the image. This option will not affect the width or height
+of the image if the user has specified a non-zero value for the
+\fB\-width\fR or \fB\-height\fR configuration option, respectively.
+.TP
+\fB\-zoom \fIx y\fR
+.
+Specifies that the source region should be magnified by a factor of
+\fIx\fR in the X direction and \fIy\fR in the Y direction. If \fIy\fR
+is not given, the default value is the same as \fIx\fR. With this
+option, each pixel in the source image will be expanded into a block
+of \fIx\fR x \fIy\fR pixels in the destination image, all the same
+color. \fIx\fR and \fIy\fR must be greater than 0.
+.TP
+\fB\-subsample \fIx y\fR
+.
+Specifies that the source image should be reduced in size by using
+only every \fIx\fRth pixel in the X direction and \fIy\fRth pixel in
+the Y direction. Negative values will cause the image to be flipped
+about the Y or X axes, respectively. If \fIy\fR is not given, the
+default value is the same as \fIx\fR.
+.TP
+\fB\-compositingrule \fIrule\fR
+.
+Specifies how transparent pixels in the source image are combined with
+the destination image. When a compositing rule of \fIoverlay\fR is
+set, the old contents of the destination image are visible, as if the
+source image were printed on a piece of transparent film and placed
+over the top of the destination. When a compositing rule of \fIset\fR
+is set, the old contents of the destination image are discarded and
+the source image is used as-is. The default compositing rule is
+\fIoverlay\fR.
+.RE
+.TP
+\fIimageName \fBdata\fR ?\fIoption value(s) ...\fR?
+.
+Returns image data in the form of a string. The following options
+may be specified:
+.RS
+.TP
+\fB\-background\fI color\fR
+.
+If the color is specified, the data will not contain any transparency
+information. In all transparent pixels the color will be replaced by
+the specified color.
+.TP
+\fB\-format\fI format-name\fR
+.
+Specifies the name of the image file format handler to be used.
+Specifically, this subcommand searches
+for the first handler whose name matches an initial substring of
+\fIformat-name\fR and which has the capability to write a string
+containing this image data.
+If this option is not given, this subcommand uses a format that
+consists of a list (one element per row) of lists (one element per
+pixel/column) of colors in
+.QW \fB#\fIrrggbb\fR
+format (where \fIrr\fR is a pair of hexadecimal digits for the red
+channel, \fIgg\fR for green, and \fIbb\fR for blue).
+.TP
+\fB\-from \fIx1 y1 x2 y2\fR
+.
+Specifies a rectangular region of \fIimageName\fR to be returned.
+If only \fIx1\fR and \fIy1\fR are specified, the region
+extends from \fI(x1,y1)\fR to the bottom-right corner of
+\fIimageName\fR. If all four coordinates are given, they specify
+diagonally opposite corners of the rectangular region, including x1,y1
+and excluding x2,y2. The default, if this option is not given, is the
+whole image.
+.TP
+\fB\-grayscale\fR
+.
+If this options is specified, the data will not contain color
+information. All pixel data will be transformed into grayscale.
+.RE
+.TP
+\fIimageName \fBget\fR \fIx y\fR
+.
+Returns the color of the pixel at coordinates (\fIx\fR,\fIy\fR) in the
+image as a list of three integers between 0 and 255, representing the
+red, green and blue components respectively.
+.TP
+\fIimageName \fBput\fR \fIdata\fR ?\fIoption value(s) ...\fR?
+.
+Sets pixels in \fI imageName\fR to the data specified in \fIdata\fR.
+This command first searches the list of image file format handlers for
+a handler that can interpret the data in \fIdata\fR, and then reads
+the image encoded within into \fIimageName\fR (the destination image).
+If \fIdata\fR does not match any known format, an attempt to interpret
+it as a (top-to-bottom) list of scan-lines is made, with each
+scan-line being a (left-to-right) list of pixel colors (see
+\fBTk_GetColor\fR for a description of valid colors.) Every scan-line
+must be of the same length. Note that when \fIdata\fR is a single
+color name, you are instructing Tk to fill a rectangular region with
+that color. The following options may be specified:
+.RS
+.TP
+\fB\-format \fIformat-name\fR
+.
+Specifies the format of the image data in \fIdata\fR.
+Specifically, only image file format handlers whose names begin with
+\fIformat-name\fR will be used while searching for an image data
+format handler to read the data.
+.TP
+\fB\-to \fIx1 y1\fR ?\fIx2 y2\fR?
+.
+Specifies the coordinates of the top-left corner (\fIx1\fR,\fIy1\fR)
+of the region of \fIimageName\fR into which the image data will be
+copied. The default position is (0,0). If \fIx2\fR,\fIy2\fR is given
+and \fIdata\fR is not large enough to cover the rectangle specified by
+this option, the image data extracted will be tiled so it covers the
+entire destination rectangle. Note that if \fIdata\fR specifies a
+single color value, then a region extending to the bottom-right corner
+represented by (\fIx2\fR,\fIy2\fR) will be filled with that color.
+.RE
+.TP
+\fIimageName \fBread\fR \fIfilename\fR ?\fIoption value(s) ...\fR?
+.
+Reads image data from the file named \fIfilename\fR into the image.
+This command first searches the list of
+image file format handlers for a handler that can interpret the data
+in \fIfilename\fR, and then reads the image in \fIfilename\fR into
+\fIimageName\fR (the destination image). The following options may be
+specified:
+.RS
+.TP
+\fB\-format \fIformat-name\fR
+.
+Specifies the format of the image data in \fIfilename\fR.
+Specifically, only image file format handlers whose names begin with
+\fIformat-name\fR will be used while searching for an image data
+format handler to read the data.
+.TP
+\fB\-from \fIx1 y1 x2 y2\fR
+.
+Specifies a rectangular sub-region of the image file data to be copied
+to the destination image. If only \fIx1\fR and \fIy1\fR are
+specified, the region extends from (\fIx1,y1\fR) to the bottom-right
+corner of the image in the image file. If all four coordinates are
+specified, they specify diagonally opposite corners or the region.
+The default, if this option is not specified, is the whole of the
+image in the image file.
+.TP
+\fB\-shrink\fR
+.
+If this option, the size of \fIimageName\fR will be reduced, if
+necessary, so that the region into which the image file data are read
+is at the bottom-right corner of the \fIimageName\fR. This option
+will not affect the width or height of the image if the user has
+specified a non-zero value for the \fB\-width\fR or \fB\-height\fR
+configuration option, respectively.
+.TP
+\fB\-to \fIx y\fR
+.
+Specifies the coordinates of the top-left corner of the region of
+\fIimageName\fR into which data from \fIfilename\fR are to be read.
+The default is (0,0).
+.RE
+.TP
+\fIimageName \fBredither\fR
+.
+The dithering algorithm used in displaying photo images propagates
+quantization errors from one pixel to its neighbors.
+If the image data for \fIimageName\fR is supplied in pieces, the
+dithered image may not be exactly correct. Normally the difference is
+not noticeable, but if it is a problem, this command can be used to
+recalculate the dithered image in each window where the image is
+displayed.
+.TP
+\fIimageName \fBtransparency \fIsubcommand \fR?\fIarg arg ...\fR?
+.
+Allows examination and manipulation of the transparency information in
+the photo image. Several subcommands are available:
+.RS
+.TP
+\fIimageName \fBtransparency get \fIx y\fR
+.
+Returns a boolean indicating if the pixel at (\fIx\fR,\fIy\fR) is
+transparent.
+.TP
+\fIimageName \fBtransparency set \fIx y boolean\fR
+.
+Makes the pixel at (\fIx\fR,\fIy\fR) transparent if \fIboolean\fR is
+true, and makes that pixel opaque otherwise.
+.RE
+.TP
+\fIimageName \fBwrite \fIfilename\fR ?\fIoption value(s) ...\fR?
+.
+Writes image data from \fIimageName\fR to a file named \fIfilename\fR.
+The following options may be specified:
+.RS
+.TP
+\fB\-background\fI color\fR
+.
+If the color is specified, the data will not contain any transparency
+information. In all transparent pixels the color will be replaced by
+the specified color.
+.TP
+\fB\-format\fI format-name\fR
+.
+Specifies the name of the image file format handler to be used to
+write the data to the file. Specifically, this subcommand searches
+for the first handler whose name matches an initial substring of
+\fIformat-name\fR and which has the capability to write an image
+file. If this option is not given, the format is guessed from
+the file extension. If that cannot be determined, this subcommand
+uses the first handler that has the capability to write an image file.
+.TP
+\fB\-from \fIx1 y1 x2 y2\fR
+.
+Specifies a rectangular region of \fIimageName\fR to be written to the
+image file. If only \fIx1\fR and \fIy1\fR are specified, the region
+extends from \fI(x1,y1)\fR to the bottom-right corner of
+\fIimageName\fR. If all four coordinates are given, they specify
+diagonally opposite corners of the rectangular region. The default,
+if this option is not given, is the whole image.
+.TP
+\fB\-grayscale\fR
+.
+If this options is specified, the data will not contain color
+information. All pixel data will be transformed into grayscale.
+.RE
+.SH "IMAGE FORMATS"
+.PP
+The photo image code is structured to allow handlers for additional
+image file formats to be added easily. The photo image code maintains
+a list of these handlers. Handlers are added to the list by
+registering them with a call to \fBTk_CreatePhotoImageFormat\fR. The
+standard Tk distribution comes with handlers for PPM/PGM, PNG and GIF
+formats, which are automatically registered on initialization.
+.PP
+When reading an image file or processing
+string data specified with the \fB\-data\fR configuration option, the
+photo image code invokes each handler in turn until one is
+found that claims to be able to read the data in the file or string.
+Usually this will find the correct handler, but if it does not, the
+user may give a format name with the \fB\-format\fR option to specify
+which handler to use. In fact the photo image code will try those
+handlers whose names begin with the string specified for the
+\fB\-format\fR option (the comparison is case-insensitive). For
+example, if the user specifies \fB\-format gif\fR, then a handler
+named GIF87 or GIF89 may be invoked, but a handler
+named JPEG may not (assuming that such handlers had been
+registered).
+.PP
+When writing image data to a file, the processing of the
+\fB\-format\fR option is slightly different: the string value given
+for the \fB\-format\fR option must begin with the complete name of the
+requested handler, and may contain additional information following
+that, which the handler can use, for example, to specify which variant
+to use of the formats supported by the handler.
+Note that not all image handlers may support writing transparency data
+to a file, even where the target image format does.
+.SS "FORMAT SUBOPTIONS"
+.PP
+.VS 8.6
+Some image formats support sub-options, which are specified at the time that
+the image is loaded using additional words in the \fB\-format\fR option. At
+the time of writing, the following are supported:
+.TP
+\fBgif \-index\fI indexValue\fR
+.
+When parsing a multi-part GIF image, Tk normally only accesses the first
+image. By giving the \fB\-index\fR sub-option, the \fIindexValue\fR'th value
+may be used instead. The \fIindexValue\fR must be an integer from 0 up to the
+number of image parts in the GIF data.
+.TP
+\fBpng \-alpha\fI alphaValue\fR
+.
+An additional alpha filtering for the overall image, which allows the
+background on which the image is displayed to show through. This usually also
+has the effect of desaturating the image. The \fIalphaValue\fR must be between
+0.0 and 1.0.
+.VE 8.6
+.SH "COLOR ALLOCATION"
+.PP
+When a photo image is displayed in a window, the photo image code
+allocates colors to use to display the image and dithers the image, if
+necessary, to display a reasonable approximation to the image using
+the colors that are available. The colors are allocated as a color
+cube, that is, the number of colors allocated is the product of the
+number of shades of red, green and blue.
+.PP
+Normally, the number of
+colors allocated is chosen based on the depth of the window. For
+example, in an 8-bit PseudoColor window, the photo image code will
+attempt to allocate seven shades of red, seven shades of green and
+four shades of blue, for a total of 198 colors. In a 1-bit StaticGray
+(monochrome) window, it will allocate two colors, black and white. In
+a 24-bit DirectColor or TrueColor window, it will allocate 256 shades
+each of red, green and blue. Fortunately, because of the way that
+pixel values can be combined in DirectColor and TrueColor windows,
+this only requires 256 colors to be allocated. If not all of the
+colors can be allocated, the photo image code reduces the number of
+shades of each primary color and tries again.
+.PP
+The user can exercise some control over the number of colors that a
+photo image uses with the \fB\-palette\fR configuration option. If
+this option is used, it specifies the maximum number of shades of
+each primary color to try to allocate. It can also be used to force
+the image to be displayed in shades of gray, even on a color display,
+by giving a single number rather than three numbers separated by
+slashes.
+.SH CREDITS
+.PP
+The photo image type was designed and implemented by Paul Mackerras,
+based on his earlier photo widget and some suggestions from
+John Ousterhout.
+.SH EXAMPLE
+.PP
+Load an image from a file and tile it to the size of a window, which
+is useful for producing a tiled background:
+.PP
+.CS
+# These lines should be called once
+\fBimage create photo\fR untiled \-file "theFile.ppm"
+\fBimage create photo\fR tiled
+
+# These lines should be called whenever .someWidget changes
+# size; a <Configure> binding is useful here
+set width [winfo width .someWidget]
+set height [winfo height .someWidget]
+tiled \fBcopy\fR untiled \-to 0 0 $width $height \-shrink
+.CE
+.PP
+.VS 8.6
+The PNG image loader allows the application of an additional alpha factor
+during loading, which is useful for generating images suitable for disabled
+buttons:
+.PP
+.CS
+\fBimage create photo\fR icon \-file "icon.png"
+\fBimage create photo\fR iconDisabled \-file "icon.png" \e
+ \-format "png \-alpha 0.5"
+button .b \-image icon \-disabledimage iconDisabled
+.CE
+.VE 8.6
+.SH "SEE ALSO"
+image(n)
+.SH KEYWORDS
+photo, image, color
+'\" Local Variables:
+'\" mode: nroff
+'\" End: