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cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]175<p>This page descibed the Image composition methods that is used to define how
176two images should be merged together in various image operations. For the
177Command Line API it is typically set using the <A
178HREF="../www/command-line-options.html#compose" >-compose</A> setting option. </p>
179
180
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]181<p>The description of composition uses abstract terminology in order to allow
182the description to be more precise, while avoiding constant values which are
183specific to a particular build configuration. Each image pixel is represented
184by red, green, and blue levels (which are equal for a gray pixel). The
185build-dependent value <em class="QR">QuantumRange</em> is the maximum integral
186value which may be stored, per pixel, in the red, green, or blue channels of
187the image. Each image pixel may also optionally (if the image matte channel is
188enabled) have an associated level of opacity, ranging from <em>opaque</em> to
189<em>transparent</em>, which may be used to determine the influence of the pixel
190color when compositing the pixel with another image pixel. If the image matte
191channel is disabled, then all pixels in the image are treated as opaque. The
192color of an opaque pixel is fully visible while the color of a transparent
193pixel color is entirely absent (pixel color is ignored).</p>
194
195<p>By definition, raster images have a rectangular shape. All image rows are of
196equal length, as are all image columns. By treating the alpha channel as a
197visual "mask" the rectangular image may be given a "shape" by treating the
198alpha channel as a cookie-cutter for the image. This is done by setting the
199pixels within the shape to be opaque, with pixels outside the shape set as
200transparent. Pixels on the boundary of the shape may be between opaque and
201transparent in order to provide antialiasing (visually smooth edges). The
202description of the composition operators use this concept of image "shape" in
203order to make the description of the operators easier to understand. While it
204is convenient to describe the operators in terms of "shapes" they are by no
205means limited to mask-style operations since they are based on continuous
206floating-point mathematics rather than simple boolean operations.</p>
207
208<p>The following alpha blending (Duff-Porter) compose methods are available:</p>
209
210<table class="doc">
211 <tbody>
212 <tr valign="top">
213 <th align="left" style="width: 8%">Method</th>
214 <th align="left">Description</th>
215 </tr>
216
217 <tr valign="top">
218 <td valign="top">clear</td>
219 <td valign="top">Both the color and the alpha of the destination are
220 cleared. Neither the source nor the destination are used (except for
221 destinations size and other meta-data which is always preserved.</td>
222 </tr>
223
224 <tr valign="top">
225 <td valign="top">src</td>
226 <td valign="top">The source is copied to the destination. The destination
227 is not used as input, though it is cleared.</td>
228 </tr>
229
230 <tr valign="top">
231 <td valign="top">dst</td>
232 <td valign="top">The destination is left untouched. The source image is
233 completely ignored.</td>
234 </tr>
235
236 <tr valign="top">
237 <td valign="top">src-over</td>
238 <td valign="top">The source is composited over the destination. this is
239 the default alpha blending compose method, when neither the compose
240 setting is set, nor is set in the image meta-data.</td>
241 </tr>
242
243 <tr valign="top">
244 <td valign="top">dst-over</td>
245 <td valign="top">The destination is composited over the source and the
246 result replaces the destination.</td>
247 </tr>
248
249 <tr valign="top">
250 <td valign="top">src-in</td>
251 <td valign="top">The part of the source lying inside of the destination
252 replaces the destination.</td>
253 </tr>
254
255 <tr valign="top">
256 <td valign="top">dst-in</td>
257 <td valign="top">The part of the destination lying inside of the source
258 replaces the destination. Areas not overlaid are cleared.</td>
259 </tr>
260
261 <tr valign="top">
262 <td valign="top">src-out</td>
263 <td valign="top">The part of the source lying outside of the destination
264 replaces the destination.</td>
265 </tr>
266
267 <tr valign="top">
268 <td valign="top">dst-out</td>
269 <td valign="top">The part of the destination lying outside of the source
270 replaces the destination.</td>
271 </tr>
272
273 <tr valign="top">
274 <td valign="top">src-atop</td>
275 <td valign="top">The part of the source lying inside of the destination is
276 composited onto the destination.</td>
277 </tr>
278
279 <tr valign="top">
280 <td valign="top">dst-atop</td>
281 <td valign="top">The part of the destination lying inside of the source is
282 composited over the source and replaces the destination. Areas not
283 overlaid are cleared. </td>
284 </tr>
285
286 <tr valign="top">
287 <td valign="top">xor</td>
288 <td valign="top">The part of the source that lies outside of the
289 destination is combined with the part of the destination that lies
290 outside of the source. Source or Destination, but not both. </td>
291 </tr>
292
293 </tbody>
294</table>
295
296<p>Any of the 'Src-*' methods can also be specified without the 'Src-' part.
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]297For example the default compose method can be specified as just 'Over'.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]298
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]299<p>Many of these compose methods will clear the destination image which was
300not overlaid by the source image. This is to be expected as part of that
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]301specific composition methods defintion. You can disable this by setting the
302special <A HREF="../www/command-line-options.html#define"
303>-define</A> 'compose:outside-overlay' to a value of 'false' will turn off
304this behaviour. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]305
306<p>On top of the above 12 Duff-Porter Alpha Composition methods, one special
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]307related method '<kbd>Copy</kbd>' has been provided. This is equivelent to
308using the '<kbd>Src</kbd>' with the special <A HREF="../www/command-line-options.html#define"
309>-define</A> option '<kbd>compose:outside-overlay</kbd>' set to
310'<kbd>false</kbd>', so as to only modify the overlaid area, without clearing
311the rest of the image outside the overlaid area. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]312
313<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]314
315<p>The following mathemathical composition methods are also available. </p>
316
317<table class="doc">
318 <tbody>
319 <tr valign="top">
320 <th align="left" style="width: 8%">Method</th>
321 <th align="left">Description</th>
322 </tr>
323
324 <tr valign="top">
325 <td valign="top">multiply</td>
326 <td valign="top">The source is multiplied by the destination and replaces
327 the destination. The resultant color is always at least as dark as
328 either of the two constituent colors. Multiplying any color with black
329 produces black. Multiplying any color with white leaves the original
330 color unchanged.</td>
331 </tr>
332
333 <tr valign="top">
334 <td valign="top">screen</td>
335 <td valign="top">The source and destination are complemented and then
336 multiplied and then replace the destination. The resultant color is
337 always at least as light as either of the two constituent colors.
338 Screening any color with white produces white. Screening any color
339 with black leaves the original color unchanged.</td>
340 </tr>
341
342 <tr valign="top">
343 <td valign="top">plus</td>
344 <td valign="top">The source is added to the destination and replaces the
345 destination. This operator is useful for averaging or a controled
346 merger of two images, rather than a direct overlay.</td>
347 </tr>
348
349 <tr valign="top">
350 <td valign="top">add</td>
351 <td valign="top">As per 'plus' but transparency data is treated as matte
352 values. As such any transparent areas in either image remain
353 transparent. </td>
354 </tr>
355
356 <tr valign="top">
357 <td valign="top">minus</td>
358 <td valign="top">Subtract the colors in the source image from the
359 destination image. When transparency is involved, opaque areas is
360 subtracted from any destination opaque areas. </td>
361 </tr>
362
363 <tr valign="top">
364 <td valign="top">subtract</td>
365 <td valign="top">Subtract the colors in the source image from the
366 destination image. When transparency is involved transparent areas are
367 subtracted, so only the opaque areas in the source remain opaque in
368 the destination image. </td>
369 </tr>
370
371 <tr valign="top">
372 <td valign="top">difference</td>
373 <td valign="top">Subtracts the darker of the two constituent colors from
374 the lighter. Painting with white inverts the destination color.
375 Painting with black produces no change.</td>
376 </tr>
377
378 <tr valign="top">
379 <td valign="top">exclusion</td>
380 <td valign="top">Produces an effect similar to that of 'difference', but
381 appears as lower contrast. Painting with white inverts the
382 destination color. Painting with black produces no change.</td>
383 </tr>
384
385 <tr valign="top">
386 <td valign="top">darken</td>
387 <td valign="top">Selects the darker of the destination and source colors.
388 The destination is replaced with the source when the source is darker,
389 otherwise it is left unchanged.</td>
390 </tr>
391
392 <tr valign="top">
393 <td valign="top">lighten</td>
394 <td valign="top">Selects the lighter of the destination and source colors.
395 The destination is replaced with the source when the source is
396 lighter, otherwise it is left unchanged. </td>
397 </tr>
398
399 </tbody>
400</table>
401
402<p>Typically these use the default 'Over' alpha blending when transparencies
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]403are also involved, except for 'Plus' which uses a 'plus' alpha blending. This
404means the alpha channel of both images will only be used to ensure that any
405visible input remains visible even in parts not overlaid. It also means that
406any values are weighted by the alpha channel of the input and output images.
407This 'Over' alpha blending is also applied to the lighting composition methods
408below. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]409
410<p>As of IM v6.6.1-6, if the special '<kbd>Sync</kbd>' flag is not specified
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]411(enabled by default) with the <a href="../www/command-line-options.html#channel"
412>-channel</a> setting, then the above mathematical compositions will nolonger
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]413syncronise its actions with the alpha channel. Instead the math composition
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]414will be applied on an individual channel basis as defined by the <a
415href="../www/command-line-options.html#channel"
416>-channel</a>. This includes the alpha channel. This special usage
417allows you to perform true mathematics of the image channels, without alpha
418compostion effects, becomming involved. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]419
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]420<p>This special flag is not applied to the lighting composition methods (see
421below) even though they are closely related to mathematical composition
422methods.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]423
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]424<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]425
426<p>The following lighting composition methods are also available. </p>
427
428<table class="doc">
429 <tbody>
430 <tr valign="top">
431 <th align="left" style="width: 8%">Method</th>
432 <th align="left">Description</th>
433 </tr>
434
435 <tr valign="top">
436 <td valign="top">linear-dodge</td>
437 <td valign="top">This is equivelent to 'Plus' in that the color channels
438 are simply added, however it does not 'Plus' the alpha channel, but
439 uses the normal 'Over' alpha blending, which transparencies are
440 involved. Produces a sort of additive multiply-like result. Added
441 ImageMagick version 6.5.4-3. </td>
442 </tr>
443
444 <tr valign="top">
445 <td valign="top">linear-burn</td>
446 <td valign="top">As 'Linear-Dodge', but also subtract one from the result.
447 Sort of a additive 'Screen' of the images. Added ImageMagick version
448 6.5.4-3. </td>
449 </tr>
450
451 <tr valign="top">
452 <td valign="top">color-dodge</td>
453 <td valign="top">Brightens the destination color to reflect the source
454 color. Painting with black produces no change.</td>
455 </tr>
456
457 <tr valign="top">
458 <td valign="top">color-burn</td>
459 <td valign="top">Darkens the destination color to reflect the source
460 color. Painting with white produces no change. Fixed in ImageMagick
461 version 6.5.4-3. </td>
462 </tr>
463
464 <tr valign="top">
465 <td valign="top">overlay</td>
466 <td valign="top">Multiplies or screens the colors, dependent on the
467 destination color. Source colors overlay the destination whilst
468 preserving its highlights and shadows. The destination color is not
469 replaced, but is mixed with the source color to reflect the lightness
470 or darkness of the destination.</td>
471 </tr>
472
473 <tr valign="top">
474 <td valign="top">hard-light</td>
475 <td valign="top">Multiplies or screens the colors, dependent on the source
476 color value. If the source color is lighter than 0.5, the destination
477 is lightened as if it were screened. If the source color is darker
478 than 0.5, the destination is darkened, as if it were multiplied. The
479 degree of lightening or darkening is proportional to the difference
480 between the source color and 0.5. If it is equal to 0.5 the
481 destination is unchanged. Painting with pure black or white produces
482 black or white.</td>
483 </tr>
484
485
486 <tr valign="top">
487 <td valign="top">linear-light</td>
488 <td valign="top">Like 'Hard-Light' but using linear-dodge and linear-burn
489 instead. Increases contrast slightly with an impact on the
490 foreground's tonal values.</td>
491 </tr>
492
493 <tr valign="top">
494 <td valign="top">soft-light</td>
495 <td valign="top">Darkens or lightens the colors, dependent on the source
496 color value. If the source color is lighter than 0.5, the destination
497 is lightened. If the source color is darker than 0.5, the destination
498 is darkened, as if it were burned in. The degree of darkening or
499 lightening is proportional to the difference between the source color
500 and 0.5. If it is equal to 0.5, the destination is unchanged. Painting
501 with pure black or white produces a distinctly darker or lighter area,
502 but does not result in pure black or white. Fixed in ImageMagick
503 version 6.5.4-3. </td>
504 </tr>
505
506 <tr valign="top">
507 <td valign="top">pegtop-light</td>
508 <td valign="top">Almost equivelent to 'Soft-Light', but using a
509 continuious mathematical formula rather than two conditionally
510 selected formulae. Added ImageMagick version 6.5.4-3. </td>
511 </tr>
512
513 <tr valign="top">
514 <td valign="top">vivid-light</td>
515 <td valign="top">A modified 'Linear-Light' designed to preserve very stong
516 primary and secondary colors in the image. Added ImageMagick version
517 6.5.4-3. </td>
518 </tr>
519
520 <tr valign="top">
521 <td valign="top">pin-light</td>
522 <td valign="top">Similar to 'Hard-Light', but using sharp linear shadings,
523 to similate the effects of a strong 'pinhole' light source. Added
524 ImageMagick version 6.5.4-3. </td>
525 </tr>
526
527 </tbody>
528</table>
529
530
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]531<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]532
533<p>Also included are these special purpose compose methods:</p>
534
535<table class="doc">
536 <tbody>
537 <tr valign="top">
538 <th align="left" style="width: 8%">Method</th>
539 <th align="left">Description</th>
540 </tr>
541
542 <tr valign="top">
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]543 <td valign="top">copy</td>
544 <td valign="top">This is equivelent to the Duff-Porter composition method
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]545 '<kbd>Src,</kbd>' but without clearing the parts of the destination
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]546 image that is not overlaid. </td>
547 </tr>
548
549 <tr valign="top">
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]550 <td valign="top">copy-*</td>
551 <td valign="top">Copy the specified channel (Red, Green, Blue, Cyan,
552 Magenta, Yellow, Black, or Opacity) in the source image to the
553 same channel in the destination image. If the channel specified
554 does not exist in the source image, (which can only happen for methods,
555 '<kbd>copy-opacity</kbd>' or '<kbd>copy-black</kbd>') then it is
556 assumed that the source image is a special grayscale channel image
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]557 of the values that is to be copied. </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]558 </tr>
559
560 <tr valign="top">
561 <td valign="top">change-mask</td>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]562 <td valign="top">Replace any destination pixel that is the similar to the
563 source images pixel (as defined by the current <a
564 href="../www/command-line-options.html#fuzz">-fuzz</a> factor), with transparency.
565 </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]566 </tr>
567 </tbody>
568</table>
569
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]570<br><br>
571
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]572<p>On top of these composed methods are a few special ones that not only require
573the two images that are being merged or overlaid, but have some extra numerical
574arguments, which are tabled below. </p>
575
576<p>In the "<code>composite</code>" command these composition methods are
577selected using special options with the arguments needed. They are usually,
578but not always, the same name as the composte 'method' they use, and replaces
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]579the normal use of the <a href="../www/command-line-options.html#compose" >-compose</a>
580setting in the "<code>composite</code>" command. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]581
582<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>composite ... -blend 50x50 ...</span></p>
583<p>As of IM v6.5.3-4 the "<code>convert</code>" command can now also supply
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]584these extra arguments to its <a href="../www/command-line-options.html#composite"
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]585>-composite</a> operator, using the special <a href="../www/command-line-options.html#define">-define</a>
586attribute of '<kbd class="arg">compose:args</kbd>'. This means you can now
587make use of these special argumented <a href="../www/command-line-options.html#compose"
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]588>-compose</a> methods, those the argument and the method both need to be set
589separatally. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]590
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]591<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert ... -compose blend -define compose:args=50,50 -composite ...</span></p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]592<p>The following is a table of these special 'argumented' compose methods,
593with a brief summary of what they do. For more details see the equivalent
594"composite" command option name. </p>
595
596<table class="doc">
597 <tbody>
598 <tr valign="top">
599 <th align="left" style="width: 8%">Method</th>
600 <th align="left">Description</th>
601 </tr>
602
603 <tr valign="top">
604 <td valign="top">dissolve</td>
605 <td valign="top">Arguments:
606 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]607 <br>Equivalent to "<code>composite</code>" <a href="../www/command-line-options.html#dissolve">-dissolve</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]608 <br>Dissolve the 'source' image by the percentage given before overlaying
609 'over' the 'destination' image. If <em class="arg">src_percent</em> is
610 greater than 100, it starts dissolving the main image so it will
611 become transparent at a value of '<kbd class="arg">200</kbd>'. If
612 both percentages are given, each image are dissolved to the
613 percentages given.
614 </td>
615 </tr>
616
617 <tr valign="top">
618 <td valign="top">blend</td>
619 <td valign="top">Arguments:
620 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]621 <br>Equivalent to "<code>composite</code>" <a
622 href="../www/command-line-options.html#blend">-blend</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]623 <br>Average the images together ('plus') according to the percentages
624 given and each pixels transparency. If only a single percentage value
625 is given it sets the weight of the composite or 'source' image, while
626 the background image is weighted by the exact opposite amount. That is
627 a <kbd>-blend 30</kbd> merges 30% of the 'source' image with 70% of
628 the 'destination' image. Thus it is equivalent to <kbd>-blend
629 30x70</kbd>.
630 </td>
631 </tr>
632
633 <tr valign="top">
634 <td valign="top">mathematics</td>
635 <td valign="top">Arguments: <em class="arg">A, B, C, D</em>
636 <br>Not available in "<code>composite</code>" at this time.
637 <br>Merge the source and destination images according to the formula
638 <br>&nbsp; &nbsp; &nbsp;<code>A*Sc*Dc + B*Sc + C*Dc + D</code>
639 <br>Can be used to generate a custom composition method that would
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]640 otherwise need to be implemented using the slow <a
641 href="../www/command-line-options.html#fx">-fx</a> DIY image operator. Added
642 to ImageMagick version 6.5.4-3.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]643 <br>As of IM v6.6.1-6 this method will do per-channel math compositions
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]644 if the 'Sync' flag is removed from <a
645 href="../www/command-line-options.html#channel" >-channel</a>, just like all
646 the other mathematical compostion methods above.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]647 </td>
648 </tr>
649
650 <tr valign="top">
651 <td valign="top">modulate</td>
652 <td valign="top">Arguments:
653 <em class="arg">brightness</em>[x<em class="arg">saturation</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]654 <br>Equivalent to "<code>composite</code>" <a href="../www/command-line-options.html#watermark">-watermark</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]655 <br>Take a grayscale image (with alpha mask) and modify the destination
656 image's brightness according to watermark image's grayscale value and
657 the <em class="arg">brightness</em> percentage. The destinations
658 color saturation attribute is just direct modified by the <em
659 class="arg">saturation</em> percentage, which defaults to 100 percent
660 (no color change).
661
662 </td>
663 </tr>
664
665 <tr valign="top">
666 <td valign="top">displace</td>
667 <td valign="top">Arguments:
668 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em>][!][%]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]669 <br>Equivalent to "<code>composite</code>" <a href="../www/command-line-options.html#displace">-displace</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]670 <br>With this option, the 'overlay' image, and optionally the 'mask'
671 image, is used as a relative displacement map, which is used to
672 displace the lookup of what part of the destination image is seen at
673 each point of the overlaid area. Much like the displacement map is a
674 'lens' that distorts the original 'background' image behind it.
675 <br><br>
676 The X-scale is modilated by the 'red' channel of the overlay image
677 while the Y-scale is modulated by the green channel, (the mask image
678 if given is rolled into green channel of the overlay image. This
679 separation allows you to modulate the X and Y lookup displacement
680 separatally allowing you to di 2 dimentional displacements, rather
681 than 1 dimentional verctored displacements (using grayscale image).
682 <br><br>
683 If the overlay image contains transparency this is used as a mask
684 of the resulting image to remove 'invalid' pixels.
685 <br><br>
686 The '%' flag makes the displacement scale relative to the size of the
687 overlay image (100% = half width/height of image). Using '!' switches
688 percentage arguments to refer to the destination image size instead.
689 <br><br>
690 Special flags were added Added to ImageMagick version 6.5.3-5.
691 </td>
692 </tr>
693
694 <tr valign="top">
695 <td valign="top">distort</td>
696 <td valign="top">Arguments:
697 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em
698 >[+<em class="arg">X-center</em>+<em class="arg">Y-center</em>]][!][%]
699 <br>Not available in "<code>composite</code>" at this time.
700 <br>Exactly as per 'Displace' (above), but using absolute coordinates,
701 relative to the center of the overlay (or that given). Basically
702 allows you to generate absolute distortion maps where 'black' will
703 look up the left/top edge, and 'white' looks up the bottom/right
704 edge of the destination image, according to the scale given.
705 <br><br>
706 The '!' flag not only switches percentage scaling, to use the
707 destination image, but also the image the center offset of the lookup.
708 This means the overlay can lookup a completely different region of the
709 destination image.
710 <br><br>
711 Added to ImageMagick version 6.5.3-5.
712 </td>
713 </tr>
714
715 <tr valign="top">
716 <td valign="top">blur</td>
717 <td valign="top">Arguments:
718 <em class="arg">Width</em>[x<em class="arg">Height</em
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]719 >[+<em class="arg">Angle</em>][+<em class="arg">Angle2</em>]]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]720 <br>Equivalent to "<code>composite</code>" <a href="../www/command-line-options.html#blur-composite">-blur</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]721 <br>A Variable Blur Mapping Composition method, where each pixel in the
722 overlaid region is replaced with an Elliptical Weighted Average (EWA),
723 with an ellipse (typically a circle) of the given sigma size, scaled
724 according to overlay (source image) grayscale mapping.
725 <br><br>
726 As per 'Displace' and 'Distort', the red channel will modulate the
727 width of the ellipse, while the green channel will modulate the height
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame^]728 of the ellipse. If a single Angle value is given in the arguments,
729 then the ellipse will then be rotated by the angle specifed.
730 <br><br>
731 Normally the blue channel of the mapping overlay image is ignored.
732 However if a second ellipse angle is given, then it is assumed that
733 the blue channel defines a variable angle for the ellipse ranging from
734 the first angle to the second angle given. This allows to generate
735 radial blurs, or a rough approximation for rotational blur. Or any mix
736 of the two.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]737 <br><br>
738 Added to ImageMagick version 6.5.4-0.
739 </td>
740 </tr>
741
742 </tbody>
743</table>
744
745<p>To print a complete list of all the available compose operators, use <a
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]746href="../www/command-line-options.html#list">-list compose</a>.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]747
748
749
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