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Diffstat (limited to 'doc/photo.n')
| -rw-r--r-- | doc/photo.n | 496 |
1 files changed, 402 insertions, 94 deletions
diff --git a/doc/photo.n b/doc/photo.n index 84cf618..bc97319 100644 --- a/doc/photo.n +++ b/doc/photo.n @@ -24,31 +24,31 @@ photo \- Full-color images \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 \fBget \fIx y\fR ?\fIoption\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 \fBtransparency \fIsubcommand \fR?\fIarg ...\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 +A photo is an image whose pixels can display any color with a varying +degree of transparency (the alpha channel). 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. +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 (semi)transparent if the image data it was obtained from had +transparency informaton. In regions where no image data has been +supplied, it is fully transparent. Transparency may also be modified +with the \fBtransparency set\fR subcommand. .SH "CREATING PHOTOS" .PP Like all images, photos are created using the \fBimage create\fR @@ -57,19 +57,25 @@ 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 +Specifies the contents of the image as a string. +.VS 8.7 +The string should +contain data in the default list-of-lists form, +.VE 8.7 +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. +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 +\fB\-format\fR {\fIformat-name\fR ?\fIoption value ...\fR?} . Specifies the name of the file format for the data specified with the -\fB\-data\fR or \fB\-file\fR option. +\fB\-data\fR or \fB\-file\fR option and optional arguments passed to +the format handler. Note: the value of this option must be a Tcl list. +This means that the braces may be omitted if the argument has only one +word. Also, instead of braces, double quotes may be used for quoting. .TP \fB\-file \fIname\fR . @@ -95,6 +101,16 @@ 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. +.VS 8.7 +.TP +\fB\-metadata \fImetadata\fR +. +Set the metadata dictionary of the image. +Additional keys may be set within the metadata dictionary of the image, +if image data is processed due to a \fB\-file\fR or \fB\-data\fR options +and the driver outputs any metadata keys. +See section \fBMETADATA DICTIONARY\fR below. +.VE 8.7 .TP \fB\-palette \fIpalette-spec\fR . @@ -122,7 +138,7 @@ 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? +\fIimageName option \fR?\fIarg ...\fR? .CE \fIOption\fR and the \fIarg\fRs determine the exact behavior of the command. @@ -140,7 +156,7 @@ The following commands are possible for photo images: . 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. +window it is displayed in will show through. The metadata dict of the image is not changed. .TP \fIimageName \fBcget\fR \fIoption\fR . @@ -163,6 +179,10 @@ 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. +.VS 8.7 +Note: setting the \fB\-metadata\fR option without any other option +will not invoke the image format driver to recreate the bitmap. +.VE 8.7 .TP \fIimageName \fBcopy\fR \fIsourceImage\fR ?\fIoption value(s) ...\fR? . @@ -233,8 +253,14 @@ the source image is used as-is. The default compositing rule is .TP \fIimageName \fBdata\fR ?\fIoption value(s) ...\fR? . -Returns image data in the form of a string. The following options -may be specified: +Returns image data in the form of a string. +.VS 8.7 +The format of the string depends on the format handler. By default, a +human readable format as a list of lists of pixel data is used, other +formats can be chosen with the \fB-format\fR option. +See \fBIMAGE FORMATS\fR below for details. +.VE 8.7 +The following options may be specified: .RS .TP \fB\-background\fI color\fR @@ -243,19 +269,23 @@ 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 +\fB\-format\fR {\fIformat-name\fR ?\fIoption value ...\fR?} +. +Specifies the name of the image file format handler to use and, +optionally, arguments to the format handler. 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. +.VS 8.7 +If this option is not given, this subcommand uses the default 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). +format (see \fBIMAGE FORMATS\fR below). +.VE 8.7 +Note: the value of this option must be a Tcl list. +This means that the braces may be omitted if the argument has only one +word. Also, instead of braces, double quotes may be used for quoting. .TP \fB\-from \fIx1 y1 x2 y2\fR . @@ -271,35 +301,59 @@ whole image. . If this options is specified, the data will not contain color information. All pixel data will be transformed into grayscale. -.RE +.VS 8.7 .TP -\fIimageName \fBget\fR \fIx y\fR +\fB\-metadata\fR \fImetadata\fR +. +Image format handler may use metadata to be included in the returned +data string. +The specified \fImetadata\fR is passed to the driver for inclusion in the +data. +If no \fB\-metadata\fR option is given, the current metadata of the +image is used. +.VE 8.7 +.RE +\fIimageName \fBget\fR \fIx y\fR ?\fB-withalpha\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. +red, green and blue components respectively. If the \fB-withalpha\fR +option is specified, the returned list will have a fourth element +representing the alpha value of the pixel as an integer between 0 and +255. +.VE 8.7 .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 +.VS 8.7 +This command 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: +See \fBIMAGE FORMATS\fR below for details on formats for image data. +.VE 8.7 +The following options may be specified: .RS .TP -\fB\-format \fIformat-name\fR +\fB\-format\fR {\fIformat-name\fR ?\fIoption value ..\fR?} . -Specifies the format of the image data in \fIdata\fR. +Specifies the format of the image data in \fIdata\fR and, optionally, +arguments to be passed to the format handler. 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. +Note: the value of this option must be a Tcl list. +This means that the braces may be omitted if the argument has only one +word. Also, instead of braces, double quotes may be used for quoting. +.VS 8.7 +.TP +\fB\-metadata\fR \fImetadata\fR +. +A specified \fImetadata\fR is passed to the image format driver when interpreting +the data. +Note: The current metadata of the image is not passed to the format driver +and is not changed by the command. +.VE 8.7 .TP \fB\-to \fIx1 y1\fR ?\fIx2 y2\fR? . @@ -308,7 +362,9 @@ 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 +entire destination rectangle. If the region specified with this opion +is smaller than the supplied \fIdata\fR, the exceeding data is silently +discarded. 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 @@ -323,12 +379,16 @@ in \fIfilename\fR, and then reads the image in \fIfilename\fR into specified: .RS .TP -\fB\-format \fIformat-name\fR +\fB\-format {\fIformat-name\fR ?\fIoption value ..\fR?} . -Specifies the format of the image data in \fIfilename\fR. +Specifies the format of the image data in \fIfilename\fR and, +optionally, additional options to the format handler. 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. +Note: the value of this option must be a Tcl list. +This means that the braces may be omitted if the argument has only one +word. Also, instead of braces, double quotes may be used for quoting. .TP \fB\-from \fIx1 y1 x2 y2\fR . @@ -339,6 +399,15 @@ 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. +.VS 8.7 +.TP +\fB\-metadata\fR \fImetadata\fR +. +A specified \fImetadata\fR is passed to the image format driver when interpreting +the data. +Note: The current metadata of the image is not passed to the format driver +and is not changed by the command. +.VE 8.7 .TP \fB\-shrink\fR . @@ -366,21 +435,31 @@ 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? +\fIimageName \fBtransparency \fIsubcommand \fR?\fIarg ...\fR? . Allows examination and manipulation of the transparency information in the photo image. Several subcommands are available: .RS +.VS 8.7 .TP -\fIimageName \fBtransparency get \fIx y\fR +\fIimageName \fBtransparency get \fIx y\fR ?\fB-alpha\fR? . -Returns a boolean indicating if the pixel at (\fIx\fR,\fIy\fR) is -transparent. +Returns true if the pixel at (\fIx\fR,\fIy\fR) is fully transparent, +false otherwise. If the option \fB-alpha\fR is passed, returns the +alpha value of the pixel instead, as an integer in the range 0 to 255. +.VE 8.7 + +.VS 8.7 .TP -\fIimageName \fBtransparency set \fIx y boolean\fR +\fIimageName \fBtransparency set \fIx y\fR \fInewVal\fR ?\fB-alpha\fR? . -Makes the pixel at (\fIx\fR,\fIy\fR) transparent if \fIboolean\fR is -true, and makes that pixel opaque otherwise. +Change the transparency of the pixel at (\fIx\fR,\fIy\fR) to +\fInewVal.\fR If no additional option is passed, \fInewVal\fR is +interpreted as a boolean and the pixel is made fully transparent if +that value is true, fully opaque otherwise. If the \fB-alpha\fR +option is passed, \fInewVal\fR is interpreted as an integral alpha +value for the pixel, which must be in the range 0 to 255. +.VE 8.7 .RE .TP \fIimageName \fBwrite \fIfilename\fR ?\fIoption value(s) ...\fR? @@ -395,15 +474,19 @@ 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 +\fB\-format\fR {\fIformat-name\fR ?\fIoption value ...\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. +write the data to the file and, optionally, options to pass to the +format handler. 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. +Note: the value of this option must be a Tcl list. +This means that the braces may be omitted if the argument has only one +word. Also, instead of braces, double quotes may be used for quoting. .TP \fB\-from \fIx1 y1 x2 y2\fR . @@ -418,6 +501,16 @@ if this option is not given, is the whole image. . If this options is specified, the data will not contain color information. All pixel data will be transformed into grayscale. +.VS 8.7 +.TP +\fB\-metadata\fR \fBmetadata\fR +. +Image format handler may use metadata to be included in the written file. +The specified \fImetadata\fR is passed to the driver for inclusion in the +file. +If no \fB\-metadata\fR option is given, the current metadata of the +image is used. +.VE 8.7 .RE .SH "IMAGE FORMATS" .PP @@ -426,20 +519,24 @@ 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 +formats, +.VS 8.7 +as well as the \fBdefault\fR handler to encode/decode image +data in a human readable form. +.VE 8.7 +These handlers 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 this case, +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 @@ -450,27 +547,163 @@ 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. +.VS 8.7 +.SS "THE DEFAULT IMAGE HANDLER" +.PP +The \fBdefault\fR image handler cannot be used to read or write data +from/to a file. Its sole purpose is to encode and decode image data in +string form in a clear text, human readable, form. The \fIimageName\fR +\fBdata\fR subcommand uses this handler when no other format is +specified. When reading image data from a string with \fIimageName\fR +\fBput\fR or the \fB-data\fR option, the default handler is treated +as the other handlers. +.PP +Image data in the \fBdefault\fR string format is a (top-to-bottom) +list of scan-lines, with each scan-line being a (left-to-right) list +of pixel data. Every scan-line has the same length. The color +and, optionally, alpha value of each pixel is specified in any of +the forms described in the \fBCOLOR FORMATS\fR section below. +.VE 8.7 + .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: +Image formats may support sub-options, wich ahre specified using +additional words in the value to the \fB\-format\fR option. These +suboptions can affect how image data is read or written to file or +string. The nature and values of these options is up to the format +handler. +The built-in handlers support these suboptions: +.VS 8.7 +.TP +\fBdefault \-colorformat\fI formatType\fR +. +The option is allowed when writing image data to a string with +\fIimageName\fR \fBdata\fR. Specifies the format to use for the color +string of each pixel. \fIformatType\fR may be one of: \fBrgb\fR to +encode pixel data in the form \fB#\fIRRGGBB\fR, \fBrgba\fR to encode +pixel data in the form \fB#\fIRRGGBBAA\fR or \fBlist\fR to encode +pixel data as a list with four elements. See \fBCOLOR FORMATS\fR +below for details. The default is \fBrgb\fR. +.VE 8.7 .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. +The option has effect when reading image data from a file. 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. +The option has effect when reading image data from a file. Specifies +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. +.TP +\fBsvg \-dpi\fI dpiValue\fB \-scale\fI scaleValue\fB \-scaletowidth \fI width\fB \-scaletoheight\fI height\fR +. +\fIdpiValue\fR is used in conversion between given coordinates and +screen resolution. The value must be greater than 0 and the default +value is 96. +\fIscaleValue\fR is used to scale the resulting image. The value must +be greater than 0 and the default value is 1. +\fIwidth\fR and \fIheight\fR are the width or height that the image +will be adjusted to. Only one parameter among \fB\-scale\fR, +\fB\-scaletowidth\fR and \fB\-scaletoheight\fR can be given at a time +and the aspect ratio of the original image is always preserved. +The svg format supports a wide range of SVG features, but the +full SVG standard is not available, for instance the 'text' feature +is missing and silently ignored when reading the SVG data. +The supported SVG features are: +. +.RS +\fB elements:\fR g, path, rect, circle, ellipse, line, polyline, polygon, +linearGradient, radialGradient, stop, defs, svg, style +.PP +\fB attributes:\fR width, height, viewBox, +preserveAspectRatio with none, xMin, xMid, xMax, yMin, yMid, yMax, slice +.PP +\fB gradient attributes:\fR gradientUnits with objectBoundingBox, +gradientTransform, cx, cy, r fx, fy x1, y1, x2, y2 +spreadMethod with pad, reflect or repeat, +xlink:href +.PP +\fB poly attributes: \fR points +.PP +\fB line attributes: \fR x1, y1, x2, y2 +.PP +\fB ellipse attributes: \fR cx, cy, rx, ry +.PP +\fB circle attributes: \fR cx, cy, r +.PP +\fB rectangle attributes: \fR x, y, width, height, rx, ry +.PP +\fB path attributes: \fR d with m, M, l, L, h, H, v, V, c, C, s, S, q, Q, t, T, a, A, z, Z +.PP +\fB style attributes: \fR display with none, visibility, hidden, visible, +fill with nonzero and evenodd, opacity, fill-opacity, +stroke, stroke-width, stroke-dasharray, stroke-dashoffset, stroke-opacity, +stroke-linecap with butt, round and square, +stroke-linejoin with miter, round and bevel, stroke-miterlimit +fill-rule, font-size, +transform with matrix, translate, scale, rotate, skewX and skewY, +stop-color, stop-opacity, offset, id, class +.RE +. +Currently only SVG images reading and conversion into (pixel-based +format) photos is supported: Tk does not (yet) support bundling photo +images in SVG vector graphics. .VE 8.6 +.VS 8.7 +.SH "COLOR FORMATS" +.PP +The default image handler can represent/parse color and alpha values +of a pixel in one of the formats listed below. If a color format does +not contain transparency information, full opacity is assumed. The +available color formats are: +.IP \(bu 3 +The empty string - interpreted as full transparency, the color value +is undefined. +.IP \(bu 3 +Any value accepted by \fBTk_GetColor\fR, optionally followed by an +alpha suffix. The alpha suffix may be one of: +.RS +.TP +\fB@\fR\fIA\fR +. +The alpha value \fIA\fR must be a fractional value in the range 0.0 +(fully transparent) to 1.0 (fully opaque). +.TP +\fB#\fR\fIX\fR +. +The alpha value \fIX\fR is a hexadecimal digit that specifies an integer +alpha value in the range 0 (fully transparent) to 255 (fully opaque). +This is expanded in range from 4 bits wide to 8 bits wide by +multiplication by 0x11. +.TP +\fB#\fR\fIXX\fR +. +The alpha value \fIXX\fR is passed as two hexadecimal digits that +specify an integer alpha value in the range 0 (fully transparent) to 255 +(fully opaque). +.RE +.IP \(bu 3 +A Tcl list with three or four integers in the range 0 to 255, +specifying the values for the red, green, blue and (optionally) +alpha channels respectively. +.IP \(bu 3 +\fB#\fR\fIRGBA\fR format: a \fB#\fR followed by four hexadecimal digits, +where each digit is the value for the red, green, blue and alpha +channels respectively. Each digit will be expanded internally to +8 bits by multiplication by 0x11. +.IP \(bu 3 +\fB#\fR\fIRRGGBBAA\fR format: \fB#\fR followed by eight hexadecimal digits, +where each pair of subsequent digits represents the value for the red, +green, blue and alpha channels respectively. +.VE 8.7 .SH "COLOR ALLOCATION" .PP When a photo image is displayed in a window, the photo image code @@ -500,6 +733,64 @@ 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. +.VS 8.7 +.SH "METADATA DICTIONARY" +.PP +Each image has a metadata dictionary property. +This dictionary is not relevant to the bitmap representation of the +image, but may contain additional information like resolution or +comments. +Image format drivers may output metadata when image data is +parsed, or may use metadata to be included in image files or formats. +.SS "METADATA KEYS (MULTIPLE FORMATS)" +.PP +Each image format driver supports an individual set of metadata dictionary +keys. Predefined keys are: +.TP +DPI +. +Horizontal image resolution in DPI as a double value. +Supported by format \fBpng\fR. +.TP +aspect +. +Aspect ratio horizontal divided by vertical as double value. +Supported by formats \fBgif\fR and \fBpng\fR. +.TP +comment +. +Image text comment. +Supported by formats \fBgif\fR and \fBpng\fR. +.PP +It is valid to set any key in the metadata dict. +A format driver will ignore keys it does not handle. +.SS "METADATA KEYS FOR ANIMATED GIF INFORMATION" +.PP +The following metadata keys are reported when reading a \fBgif\fR format file. +They are typically used in conjunction with the \fI-index\fR option of an +animated \fBgif\fR file to properly display the subimage sequence. +The options are linked to each subimage selected by \fI-index\fR. +.TP +\fBdelay time\fR \fItime\fR +. +Update delay time in 10ms unit. This key is only present, if delay time is not 0. +.TP +\fBdisposal method\fR \fImethod\fR +. +Disposal method of the preceeding image, if given for the current image. +Possible values are: \fIdo not dispose\fR, \fIrestore to background color\fR, \fIrestore to previous\fR. +.TP +\fBuser interaction\fR \fIbool\fR +. +The key is present with a value of 1, if user interaction is specified. +Otherwise, the key is not present. +.TP +\fBupdate region\fR \fIX0\fR, \fIY0\fR, \fIwidth\fR, \fIheight\fR +. +Update region of the current subimage, if subimage has not the same size as +the full image. The pixel outside of this box are all fully transparent. +.PP +.VE 8.7 .SH CREDITS .PP The photo image type was designed and implemented by Paul Mackerras, @@ -534,6 +825,23 @@ buttons: button .b \-image icon \-disabledimage iconDisabled .CE .VE 8.6 +.PP +.VS 8.7 +Create a green box with a simple shadow effect +.PP +.CS +\fBimage create photo\fR foo + +# Make a simple graduated fill varying in alpha for the shadow +for {set i 14} {$i > 0} {incr i -1} { + set i2 [expr {$i + 30}] + foo \fBput\fR [format black#%x [expr {15-$i}]] -to $i $i $i2 $i2 +} + +# Put a solid green rectangle on top +foo \fBput\fR #F080 -to 0 0 30 30 +.VE 8.7 +.CE .SH "SEE ALSO" image(n) .SH KEYWORDS |