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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "PHOTO 1" |
| 132 | .TH PHOTO 1 "2000-12-30" "perl v5.8.0" "User Contributed Perl Documentation" |
| 133 | .SH "NAME" |
| 134 | Tk::Photo \- Full\-color images |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | \&\ \fI$widget\fR\->\fBPhoto\fR(?\fIname\fR??, \fIoptions\fR?) |
| 138 | .SH "DESCRIPTION" |
| 139 | .IX Header "DESCRIPTION" |
| 140 | A photo is an image whose pixels can display any color or be |
| 141 | transparent. A photo image is stored internally in full color (32 |
| 142 | bits per pixel), and is displayed using dithering if necessary. Image |
| 143 | data for a photo image can be obtained from a file or a string, or it |
| 144 | can be supplied from |
| 145 | C code through a procedural interface. At present, only \s-1GIF\s0 and \s-1PPM/PGM\s0 |
| 146 | formats are supported, but an interface exists to allow additional |
| 147 | image file formats to be added easily. A photo image is transparent |
| 148 | in regions where no image data has been supplied. |
| 149 | .SH "CREATING PHOTOS" |
| 150 | .IX Header "CREATING PHOTOS" |
| 151 | Photos are created using the \fBPhoto\fR method. |
| 152 | \&\fBPhoto\fR supports the following \fIoptions\fR: |
| 153 | .IP "\fB\-data\fR => \fIstring\fR" 4 |
| 154 | .IX Item "-data => string" |
| 155 | Specifies the contents of the image as a string. The format of the |
| 156 | string must be one of those for which there is an image file format |
| 157 | handler that will accept string data. If both the \fB\-data\fR |
| 158 | and \fB\-file\fR options are specified, the \fB\-file\fR option takes |
| 159 | precedence. |
| 160 | .IP "\fB\-format\fR => \fIformat-name\fR" 4 |
| 161 | .IX Item "-format => format-name" |
| 162 | Specifies the name of the file format for the data specified with the |
| 163 | \&\fB\-data\fR or \fB\-file\fR option. |
| 164 | .IP "\fB\-file\fR => \fIname\fR" 4 |
| 165 | .IX Item "-file => name" |
| 166 | \&\fIname\fR gives the name of a file that is to be read to supply data |
| 167 | for the photo image. The file format must be one of those for which |
| 168 | there is an image file format handler that can read data. |
| 169 | .IP "\fB\-gamma\fR => \fIvalue\fR" 4 |
| 170 | .IX Item "-gamma => value" |
| 171 | Specifies that the colors allocated for displaying this image in a |
| 172 | window should be corrected for a non-linear display with the specified |
| 173 | gamma exponent value. (The intensity produced by most |
| 174 | \&\s-1CRT\s0 displays is a power function of the input value, to a good |
| 175 | approximation; gamma is the exponent and is typically around 2). |
| 176 | The value specified must be greater than zero. The default |
| 177 | value is one (no correction). In general, values greater than one |
| 178 | will make the image lighter, and values less than one will make it |
| 179 | darker. |
| 180 | .IP "\fB\-height\fR => \fInumber\fR" 4 |
| 181 | .IX Item "-height => number" |
| 182 | Specifies the height of the image, in pixels. This option is useful |
| 183 | primarily in situations where the user wishes to build up the contents |
| 184 | of the image piece by piece. A value of zero (the default) allows the |
| 185 | image to expand or shrink vertically to fit the data stored in it. |
| 186 | .IP "\fB\-palette\fR => \fIpalette-spec\fR" 4 |
| 187 | .IX Item "-palette => palette-spec" |
| 188 | Specifies the resolution of the color cube to be allocated for |
| 189 | displaying this image, and thus the number of colors used from the |
| 190 | colormaps of the windows where it is displayed. The |
| 191 | \&\fIpalette-spec\fR string may be either a single decimal number, |
| 192 | specifying the number of shades of gray to use, or three decimal |
| 193 | numbers separated by slashes (/), specifying the number of shades of |
| 194 | red, green and blue to use, respectively. If the first form (a single |
| 195 | number) is used, the image will be displayed in monochrome (i.e., |
| 196 | grayscale). |
| 197 | .IP "\fB\-width\fR => \fInumber\fR" 4 |
| 198 | .IX Item "-width => number" |
| 199 | Specifies the width of the image, in pixels. This option is useful |
| 200 | primarily in situations where the user wishes to build up the contents |
| 201 | of the image piece by piece. A value of zero (the default) allows the |
| 202 | image to expand or shrink horizontally to fit the data stored in it. |
| 203 | .SH "IMAGE METHODS" |
| 204 | .IX Header "IMAGE METHODS" |
| 205 | When a photo image is created, Tk also creates a new object. |
| 206 | This object supports the \fBconfigure\fR and \fBcget\fR methods |
| 207 | described in Tk::options which can be used to enquire and |
| 208 | modify the options described above. |
| 209 | .PP |
| 210 | Those options that write data to the image generally expand the size |
| 211 | of the image, if necessary, to accommodate the data written to the |
| 212 | image, unless the user has specified non-zero values for the |
| 213 | \&\fB\-width\fR and/or \fB\-height\fR configuration options, in which |
| 214 | case the width and/or height, respectively, of the image will not be |
| 215 | changed. |
| 216 | .PP |
| 217 | The following addition methods are available for photo images: |
| 218 | .IP "\fI$image\fR\->\fBblank\fR" 4 |
| 219 | .IX Item "$image->blank" |
| 220 | Blank the image; that is, set the entire image to have no data, so it |
| 221 | will be displayed as transparent, and the background of whatever |
| 222 | window it is displayed in will show through. |
| 223 | .IP "\fI$image\fR\->\fBcopy\fR(\fIsourceImage\fR ?,\fIoption value(s) ...\fR?)" 4 |
| 224 | .IX Item "$image->copy(sourceImage ?,option value(s) ...?)" |
| 225 | Copies a region from the image called \fIsourceImage\fR (which must |
| 226 | be a photo image) to the image called \fI$image\fR, possibly with |
| 227 | pixel zooming and/or subsampling. If no options are specified, this |
| 228 | method copies the whole of \fIsourceImage\fR into \fI$image\fR, |
| 229 | starting at coordinates (0,0) in \fI$image\fR. The following |
| 230 | options may be specified: |
| 231 | .RS 4 |
| 232 | .IP "\fB\-from\fR => \fIx1 y1 ?x2 y2?\fR" 8 |
| 233 | .IX Item "-from => x1 y1 ?x2 y2?" |
| 234 | Specifies a rectangular sub-region of the source image to be copied. |
| 235 | (\fIx1,y1\fR) and (\fIx2,y2\fR) specify diagonally opposite corners of |
| 236 | the rectangle. If \fIx2\fR and \fIy2\fR are not specified, the |
| 237 | default value is the bottom-right corner of the source image. The |
| 238 | pixels copied will include the left and top edges of the specified |
| 239 | rectangle but not the bottom or right edges. If the \fB\-from\fR |
| 240 | option is not given, the default is the whole source image. |
| 241 | .IP "\fB\-to\fR => \fIx1 y1 ?x2 y2?\fR" 8 |
| 242 | .IX Item "-to => x1 y1 ?x2 y2?" |
| 243 | Specifies a rectangular sub-region of the destination image to be |
| 244 | affected. (\fIx1,y1\fR) and (\fIx2,y2\fR) specify diagonally opposite |
| 245 | corners of the rectangle. If \fIx2\fR and \fIy2\fR are not specified, |
| 246 | the default value is (\fIx1,y1\fR) plus the size of the source |
| 247 | region (after subsampling and zooming, if specified). If \fIx2\fR and |
| 248 | \&\fIy2\fR are specified, the source region will be replicated if |
| 249 | necessary to fill the destination region in a tiled fashion. |
| 250 | .IP "\fB\-shrink\fR" 8 |
| 251 | .IX Item "-shrink" |
| 252 | Specifies that the size of the destination image should be reduced, if |
| 253 | necessary, so that the region being copied into is at the bottom-right |
| 254 | corner of the image. This option will not affect the width or height |
| 255 | of the image if the user has specified a non-zero value for the |
| 256 | \&\fB\-width\fR or \fB\-height\fR configuration option, respectively. |
| 257 | .IP "\fB\-zoom\fR => \fIx y\fR" 8 |
| 258 | .IX Item "-zoom => x y" |
| 259 | Specifies that the source region should be magnified by a factor of |
| 260 | \&\fIx\fR in the X direction and \fIy\fR in the Y direction. If \fIy\fR |
| 261 | is not given, the default value is the same as \fIx\fR. With this |
| 262 | option, each pixel in the source image will be expanded into a block |
| 263 | of \fIx\fR x \fIy\fR pixels in the destination image, all the same |
| 264 | color. \fIx\fR and \fIy\fR must be greater than 0. |
| 265 | .IP "\fB\-subsample\fR => \fIx y\fR" 8 |
| 266 | .IX Item "-subsample => x y" |
| 267 | Specifies that the source image should be reduced in size by using |
| 268 | only every \fIx\fRth pixel in the X direction and \fIy\fRth pixel in |
| 269 | the Y direction. Negative values will cause the image to be flipped |
| 270 | about the Y or X axes, respectively. If \fIy\fR is not given, the |
| 271 | default value is the same as \fIx\fR. |
| 272 | .RE |
| 273 | .RS 4 |
| 274 | .RE |
| 275 | .IP "\fI$image\fR\->\fBdata\fR(?\fIoption value(s), ...\fR?)" 4 |
| 276 | .IX Item "$image->data(?option value(s), ...?)" |
| 277 | returns image data in the form of a string. |
| 278 | The following options may be specified: |
| 279 | .RS 4 |
| 280 | .IP "\fB\-background\fR => \fI color\fR" 8 |
| 281 | .IX Item "-background => color" |
| 282 | If the color is specified, the data will not contain any transparency |
| 283 | information. In all transparent pixels the color will be replaced by |
| 284 | the specified color. |
| 285 | .IP "\fB\-format\fR => \fIformat-name\fR" 8 |
| 286 | .IX Item "-format => format-name" |
| 287 | Specifies the name of the image file format handler to be used to |
| 288 | convert the data. Specifically, this method searches |
| 289 | for the first handler whose name matches a initial substring of |
| 290 | \&\fIformat-name\fR and which has the capability to write an string. |
| 291 | If this option is not given, the data is returned in the default |
| 292 | format as accepted by \fI$image\fR\->\fBput\fR. |
| 293 | .IP "\fB\-from\fR => \fIx1 y1 ?x2 y2?\fR" 8 |
| 294 | .IX Item "-from => x1 y1 ?x2 y2?" |
| 295 | Specifies a rectangular region of \fI$image\fR to be written to the |
| 296 | string. If only \fIx1\fR and \fIy1\fR are specified, the region |
| 297 | extends from \fI(x1,y1)\fR to the bottom-right corner of |
| 298 | \&\fI$image\fR. If all four coordinates are given, they specify |
| 299 | diagonally opposite corners of the rectangular region. The default, |
| 300 | if this option is not given, is the whole image. |
| 301 | .RE |
| 302 | .RS 4 |
| 303 | .RE |
| 304 | .IP "\fB\-grayscale\fR" 4 |
| 305 | .IX Item "-grayscale" |
| 306 | If this options is specified, the data will not contain color |
| 307 | information. All pixel data will be transformed into grayscale. |
| 308 | .IP "\fI$image\fR\->\fBget\fR(\fIx,y\fR)" 4 |
| 309 | .IX Item "$image->get(x,y)" |
| 310 | Returns the color of the pixel at coordinates (\fIx\fR,\fIy\fR) in the |
| 311 | image as a list of three integers between 0 and 255, representing the |
| 312 | red, green and blue components respectively. |
| 313 | .IP "\fI$image\fR\->\fBput\fR(\fIdata\fR ?,\fB\-format\fR=>\fIformat-name\fR? ?,\fB\-to\fR=>\fI x1 y1 ?x2 y2?\fR?)" 4 |
| 314 | .IX Item "$image->put(data ?,-format=>format-name? ?,-to=> x1 y1 ?x2 y2??)" |
| 315 | Sets pixels in \fI imageName\fR to the data specified in |
| 316 | \&\fIdata\fR. This command first searches the list of image file |
| 317 | format handlers for a handler that can interpret the data |
| 318 | in \fIdata\fR, and then reads the image in \fIfilename\fR into |
| 319 | \&\fIimageName\fR (the destination image). The following options |
| 320 | may be specified: |
| 321 | .RS 4 |
| 322 | .IP "\fB\-format \fR\fIformat-name\fR" 4 |
| 323 | .IX Item "-format format-name" |
| 324 | Specifies the format of the image data in \fIdata\fR. |
| 325 | Specifically, only image file format handlers whose names begin with |
| 326 | \&\fIformat-name\fR will be used while searching for an image data |
| 327 | format handler to read the data. Otherwise \fIdata\fR is used to form a two-dimensional array of pixels |
| 328 | that are then copied into the \fI$image\fR. \fIdata\fR is structured |
| 329 | then as a list of horizontal rows, from top to bottom, each of which is |
| 330 | a list of colors, listed from left to right. Each color may be specified |
| 331 | by name (e.g., blue) or in hexadecimal form (e.g., #2376af). |
| 332 | .IP "\fB\-from \fR\fIx1 y1 x2 y2\fR" 4 |
| 333 | .IX Item "-from x1 y1 x2 y2" |
| 334 | Specifies a rectangular sub-region of the image file data to be |
| 335 | returned. If only \fIx1\fR and \fIy1\fR are specified, the region |
| 336 | extends from (\fIx1,y1\fR) to the bottom-right corner of the image |
| 337 | in the image file. If all four coordinates are specified, they |
| 338 | specify diagonally opposite corners or the region. The default, |
| 339 | if this option is not specified, is the whole of the image. |
| 340 | .IP "\fB\-shrink\fR" 4 |
| 341 | .IX Item "-shrink" |
| 342 | If this option, the size of \fIimageName\fR will be reduced, if |
| 343 | necessary, so that the region into which the image file data are read |
| 344 | is at the bottom-right corner of the \fIimageName\fR. This option |
| 345 | will not affect the width or height of the image if the user has |
| 346 | specified a non-zero value for the \fB\-width\fR or \fB\-height\fR |
| 347 | configuration option, respectively. |
| 348 | .IP "\fB\-to \fR\fIx y\fR" 4 |
| 349 | .IX Item "-to x y" |
| 350 | Specifies the coordinates of the top-left corner of the region of |
| 351 | \&\fIimageName\fR into which data from \fIfilename\fR are to be read. |
| 352 | The default is (0,0). |
| 353 | .RE |
| 354 | .RS 4 |
| 355 | .RE |
| 356 | .IP "\fI$image\fR\->\fBread\fR(\fIfilename\fR ?,\fIoption value(s), ...\fR?)" 4 |
| 357 | .IX Item "$image->read(filename ?,option value(s), ...?)" |
| 358 | Reads image data from the file named \fIfilename\fR into the image. |
| 359 | This method first searches the list of |
| 360 | image file format handlers for a handler that can interpret the data |
| 361 | in \fIfilename\fR, and then reads the image in \fIfilename\fR into |
| 362 | \&\fI$image\fR (the destination image). The following options may be |
| 363 | specified: |
| 364 | .RS 4 |
| 365 | .IP "\fB\-format\fR => \fIformat-name\fR" 8 |
| 366 | .IX Item "-format => format-name" |
| 367 | Specifies the format of the image data in \fIfilename\fR. |
| 368 | Specifically, only image file format handlers whose names begin with |
| 369 | \&\fIformat-name\fR will be used while searching for an image data |
| 370 | format handler to read the data. |
| 371 | .IP "\fB\-from\fR => \fIx1 y1 ?x2 y2?\fR" 8 |
| 372 | .IX Item "-from => x1 y1 ?x2 y2?" |
| 373 | Specifies a rectangular sub-region of the image file data to be copied |
| 374 | to the destination image. If only \fIx1\fR and \fIy1\fR are |
| 375 | specified, the region extends from (\fIx1,y1\fR) to the bottom-right |
| 376 | corner of the image in the image file. If all four coordinates are |
| 377 | specified, they specify diagonally opposite corners or the region. |
| 378 | The default, if this option is not specified, is the whole of the |
| 379 | image in the image file. |
| 380 | .IP "\fB\-shrink\fR" 8 |
| 381 | .IX Item "-shrink" |
| 382 | If this option, the size of \fI$image\fR will be reduced, if |
| 383 | necessary, so that the region into which the image file data are read |
| 384 | is at the bottom-right corner of the \fI$image\fR. This option |
| 385 | will not affect the width or height of the image if the user has |
| 386 | specified a non-zero value for the \fB\-width\fR or \fB\-height\fR |
| 387 | configuration option, respectively. |
| 388 | .IP "\fB\-to\fR => \fIx y\fR" 8 |
| 389 | .IX Item "-to => x y" |
| 390 | Specifies the coordinates of the top-left corner of the region of |
| 391 | \&\fI$image\fR into which data from \fIfilename\fR are to be read. |
| 392 | The default is (0,0). |
| 393 | .RE |
| 394 | .RS 4 |
| 395 | .RE |
| 396 | .IP "\fI$image\fR\->\fBredither\fR" 4 |
| 397 | .IX Item "$image->redither" |
| 398 | The dithering algorithm used in displaying photo images propagates |
| 399 | quantization errors from one pixel to its neighbors. |
| 400 | If the image data for \fI$image\fR is supplied in pieces, the |
| 401 | dithered image may not be exactly correct. Normally the difference is |
| 402 | not noticeable, but if it is a problem, this method can be used to |
| 403 | recalculate the dithered image in each window where the image is |
| 404 | displayed. |
| 405 | .IP "\fI$image\fR\->\fBwrite\fR(\fIfilename\fR ?,\fIoption value(s), ...\fR?)" 4 |
| 406 | .IX Item "$image->write(filename ?,option value(s), ...?)" |
| 407 | Writes image data from \fI$image\fR to a file named \fIfilename\fR. |
| 408 | The following options may be specified: |
| 409 | .RS 4 |
| 410 | .IP "\fB\-background\fR\fI color\fR" 8 |
| 411 | .IX Item "-background color" |
| 412 | If the color is specified, the data will not contain any transparency |
| 413 | information. In all transparent pixels the color will be replaced by |
| 414 | the specified color. |
| 415 | .IP "\fB\-format\fR => \fIformat-name\fR" 8 |
| 416 | .IX Item "-format => format-name" |
| 417 | Specifies the name of the image file format handler to be used to |
| 418 | write the data to the file. Specifically, this subcommand searches |
| 419 | for the first handler whose name matches a initial substring of |
| 420 | \&\fIformat-name\fR and which has the capability to write an image |
| 421 | file. If this option is not given, this subcommand uses the first |
| 422 | handler that has the capability to write an image file. |
| 423 | .IP "\fB\-from\fR => \fIx1 y1 ?x2 y2?\fR" 8 |
| 424 | .IX Item "-from => x1 y1 ?x2 y2?" |
| 425 | Specifies a rectangular region of \fI$image\fR to be written to the |
| 426 | image file. If only \fIx1\fR and \fIy1\fR are specified, the region |
| 427 | extends from \fI(x1,y1)\fR to the bottom-right corner of |
| 428 | \&\fI$image\fR. If all four coordinates are given, they specify |
| 429 | diagonally opposite corners of the rectangular region. The default, |
| 430 | if this option is not given, is the whole image. |
| 431 | .IP "\fB\-grayscale\fR" 8 |
| 432 | .IX Item "-grayscale" |
| 433 | If this options is specified, the data will not contain color |
| 434 | information. All pixel data will be transformed into grayscale. |
| 435 | .RE |
| 436 | .RS 4 |
| 437 | .RE |
| 438 | .SH "IMAGE FORMATS" |
| 439 | .IX Header "IMAGE FORMATS" |
| 440 | The photo image code is structured to allow handlers for additional |
| 441 | image file formats to be added easily. The photo image code maintains |
| 442 | a list of these handlers. Handlers are added to the list by |
| 443 | registering them with a call to \fBTk_CreatePhotoImageFormat\fR. The |
| 444 | standard Tk distribution comes with handlers for \s-1PPM/PGM\s0 and \s-1GIF\s0 formats, |
| 445 | which are automatically registered on initialization. |
| 446 | .PP |
| 447 | When reading an image file or processing |
| 448 | string data specified with the \fB\-data\fR configuration option, the |
| 449 | photo image code invokes each handler in turn until one is |
| 450 | found that claims to be able to read the data in the file or string. |
| 451 | Usually this will find the correct handler, but if it doesn't, the |
| 452 | user may give a format name with the \fB\-format\fR option to specify |
| 453 | which handler to use. In fact the photo image code will try those |
| 454 | handlers whose names begin with the string specified for the |
| 455 | \&\fB\-format\fR option (the comparison is case\-insensitive). For |
| 456 | example, if the user specifies \fB\-format gif\fR, then a handler |
| 457 | named \s-1GIF87\s0 or \s-1GIF89\s0 may be invoked, but a handler |
| 458 | named \s-1JPEG\s0 may not (assuming that such handlers had been |
| 459 | registered). |
| 460 | .PP |
| 461 | When writing image data to a file, the processing of the |
| 462 | \&\fB\-format\fR option is slightly different: the string value given |
| 463 | for the \fB\-format\fR option must begin with the complete name of the |
| 464 | requested handler, and may contain additional information following |
| 465 | that, which the handler can use, for example, to specify which variant |
| 466 | to use of the formats supported by the handler. |
| 467 | .SH "COLOR ALLOCATION" |
| 468 | .IX Header "COLOR ALLOCATION" |
| 469 | When a photo image is displayed in a window, the photo image code |
| 470 | allocates colors to use to display the image and dithers the image, if |
| 471 | necessary, to display a reasonable approximation to the image using |
| 472 | the colors that are available. The colors are allocated as a color |
| 473 | cube, that is, the number of colors allocated is the product of the |
| 474 | number of shades of red, green and blue. |
| 475 | .PP |
| 476 | Normally, the number of |
| 477 | colors allocated is chosen based on the depth of the window. For |
| 478 | example, in an 8\-bit PseudoColor window, the photo image code will |
| 479 | attempt to allocate seven shades of red, seven shades of green and |
| 480 | four shades of blue, for a total of 198 colors. In a 1\-bit StaticGray |
| 481 | (monochrome) window, it will allocate two colors, black and white. In |
| 482 | a 24\-bit DirectColor or TrueColor window, it will allocate 256 shades |
| 483 | each of red, green and blue. Fortunately, because of the way that |
| 484 | pixel values can be combined in DirectColor and TrueColor windows, |
| 485 | this only requires 256 colors to be allocated. If not all of the |
| 486 | colors can be allocated, the photo image code reduces the number of |
| 487 | shades of each primary color and tries again. |
| 488 | .PP |
| 489 | The user can exercise some control over the number of colors that a |
| 490 | photo image uses with the \fB\-palette\fR configuration option. If |
| 491 | this option is used, it specifies the maximum number of shades of |
| 492 | each primary color to try to allocate. It can also be used to force |
| 493 | the image to be displayed in shades of gray, even on a color display, |
| 494 | by giving a single number rather than three numbers separated by |
| 495 | slashes. |
| 496 | .SH "CREDITS" |
| 497 | .IX Header "CREDITS" |
| 498 | The photo image type was designed and implemented by Paul Mackerras, |
| 499 | based on his earlier photo widget and some suggestions from |
| 500 | John Ousterhout. |
| 501 | .SH "SEE ALSO" |
| 502 | .IX Header "SEE ALSO" |
| 503 | Tk::Bitmap |
| 504 | Tk::Image |
| 505 | Tk::Pixmap |
| 506 | .SH "KEYWORDS" |
| 507 | .IX Header "KEYWORDS" |
| 508 | photo, image, color |