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cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]197<h1>ImageMagick Image Composition</h1>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]198<p>This page descibed the Image composition methods that is used to define how
199two images should be merged together in various image operations. For the
200Command Line API it is typically set using the <A
201HREF="../www/command-line-options.html#compose" >-compose</A> setting option. </p>
202
203
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]204<p>The description of composition uses abstract terminology in order to allow
205the description to be more precise, while avoiding constant values which are
206specific to a particular build configuration. Each image pixel is represented
207by red, green, and blue levels (which are equal for a gray pixel). The
208build-dependent value <em class="QR">QuantumRange</em> is the maximum integral
209value which may be stored, per pixel, in the red, green, or blue channels of
210the image. Each image pixel may also optionally (if the image matte channel is
211enabled) have an associated level of opacity, ranging from <em>opaque</em> to
212<em>transparent</em>, which may be used to determine the influence of the pixel
213color when compositing the pixel with another image pixel. If the image matte
214channel is disabled, then all pixels in the image are treated as opaque. The
215color of an opaque pixel is fully visible while the color of a transparent
216pixel color is entirely absent (pixel color is ignored).</p>
217
218<p>By definition, raster images have a rectangular shape. All image rows are of
219equal length, as are all image columns. By treating the alpha channel as a
220visual "mask" the rectangular image may be given a "shape" by treating the
221alpha channel as a cookie-cutter for the image. This is done by setting the
222pixels within the shape to be opaque, with pixels outside the shape set as
223transparent. Pixels on the boundary of the shape may be between opaque and
224transparent in order to provide antialiasing (visually smooth edges). The
225description of the composition operators use this concept of image "shape" in
226order to make the description of the operators easier to understand. While it
227is convenient to describe the operators in terms of "shapes" they are by no
228means limited to mask-style operations since they are based on continuous
229floating-point mathematics rather than simple boolean operations.</p>
230
231<p>The following alpha blending (Duff-Porter) compose methods are available:</p>
232
233<table class="doc">
234 <tbody>
235 <tr valign="top">
236 <th align="left" style="width: 8%">Method</th>
237 <th align="left">Description</th>
238 </tr>
239
240 <tr valign="top">
241 <td valign="top">clear</td>
242 <td valign="top">Both the color and the alpha of the destination are
243 cleared. Neither the source nor the destination are used (except for
244 destinations size and other meta-data which is always preserved.</td>
245 </tr>
246
247 <tr valign="top">
248 <td valign="top">src</td>
249 <td valign="top">The source is copied to the destination. The destination
250 is not used as input, though it is cleared.</td>
251 </tr>
252
253 <tr valign="top">
254 <td valign="top">dst</td>
255 <td valign="top">The destination is left untouched. The source image is
256 completely ignored.</td>
257 </tr>
258
259 <tr valign="top">
260 <td valign="top">src-over</td>
261 <td valign="top">The source is composited over the destination. this is
262 the default alpha blending compose method, when neither the compose
263 setting is set, nor is set in the image meta-data.</td>
264 </tr>
265
266 <tr valign="top">
267 <td valign="top">dst-over</td>
268 <td valign="top">The destination is composited over the source and the
269 result replaces the destination.</td>
270 </tr>
271
272 <tr valign="top">
273 <td valign="top">src-in</td>
274 <td valign="top">The part of the source lying inside of the destination
275 replaces the destination.</td>
276 </tr>
277
278 <tr valign="top">
279 <td valign="top">dst-in</td>
280 <td valign="top">The part of the destination lying inside of the source
281 replaces the destination. Areas not overlaid are cleared.</td>
282 </tr>
283
284 <tr valign="top">
285 <td valign="top">src-out</td>
286 <td valign="top">The part of the source lying outside of the destination
287 replaces the destination.</td>
288 </tr>
289
290 <tr valign="top">
291 <td valign="top">dst-out</td>
292 <td valign="top">The part of the destination lying outside of the source
293 replaces the destination.</td>
294 </tr>
295
296 <tr valign="top">
297 <td valign="top">src-atop</td>
298 <td valign="top">The part of the source lying inside of the destination is
299 composited onto the destination.</td>
300 </tr>
301
302 <tr valign="top">
303 <td valign="top">dst-atop</td>
304 <td valign="top">The part of the destination lying inside of the source is
305 composited over the source and replaces the destination. Areas not
306 overlaid are cleared. </td>
307 </tr>
308
309 <tr valign="top">
310 <td valign="top">xor</td>
311 <td valign="top">The part of the source that lies outside of the
312 destination is combined with the part of the destination that lies
313 outside of the source. Source or Destination, but not both. </td>
314 </tr>
315
316 </tbody>
317</table>
318
319<p>Any of the 'Src-*' methods can also be specified without the 'Src-' part.
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]320For example the default compose method can be specified as just 'Over'.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]321
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]322<p>Many of these compose methods will clear the destination image which was
323not overlaid by the source image. This is to be expected as part of that
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]324specific composition methods defintion. You can disable this by setting the
325special <A HREF="../www/command-line-options.html#define"
326>-define</A> 'compose:outside-overlay' to a value of 'false' will turn off
327this behaviour. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]328
329<p>On top of the above 12 Duff-Porter Alpha Composition methods, one special
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]330related method '<kbd>Copy</kbd>' has been provided. This is equivelent to
331using the '<kbd>Src</kbd>' with the special <A HREF="../www/command-line-options.html#define"
332>-define</A> option '<kbd>compose:outside-overlay</kbd>' set to
333'<kbd>false</kbd>', so as to only modify the overlaid area, without clearing
334the rest of the image outside the overlaid area. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]335
336<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]337
338<p>The following mathemathical composition methods are also available. </p>
339
340<table class="doc">
341 <tbody>
342 <tr valign="top">
343 <th align="left" style="width: 8%">Method</th>
344 <th align="left">Description</th>
345 </tr>
346
347 <tr valign="top">
348 <td valign="top">multiply</td>
349 <td valign="top">The source is multiplied by the destination and replaces
350 the destination. The resultant color is always at least as dark as
351 either of the two constituent colors. Multiplying any color with black
352 produces black. Multiplying any color with white leaves the original
353 color unchanged.</td>
354 </tr>
355
356 <tr valign="top">
357 <td valign="top">screen</td>
358 <td valign="top">The source and destination are complemented and then
359 multiplied and then replace the destination. The resultant color is
360 always at least as light as either of the two constituent colors.
361 Screening any color with white produces white. Screening any color
362 with black leaves the original color unchanged.</td>
363 </tr>
364
365 <tr valign="top">
366 <td valign="top">plus</td>
367 <td valign="top">The source is added to the destination and replaces the
368 destination. This operator is useful for averaging or a controled
369 merger of two images, rather than a direct overlay.</td>
370 </tr>
371
372 <tr valign="top">
373 <td valign="top">add</td>
374 <td valign="top">As per 'plus' but transparency data is treated as matte
375 values. As such any transparent areas in either image remain
376 transparent. </td>
377 </tr>
378
379 <tr valign="top">
380 <td valign="top">minus</td>
381 <td valign="top">Subtract the colors in the source image from the
382 destination image. When transparency is involved, opaque areas is
383 subtracted from any destination opaque areas. </td>
384 </tr>
385
386 <tr valign="top">
387 <td valign="top">subtract</td>
388 <td valign="top">Subtract the colors in the source image from the
389 destination image. When transparency is involved transparent areas are
390 subtracted, so only the opaque areas in the source remain opaque in
391 the destination image. </td>
392 </tr>
393
394 <tr valign="top">
395 <td valign="top">difference</td>
396 <td valign="top">Subtracts the darker of the two constituent colors from
397 the lighter. Painting with white inverts the destination color.
398 Painting with black produces no change.</td>
399 </tr>
400
401 <tr valign="top">
402 <td valign="top">exclusion</td>
403 <td valign="top">Produces an effect similar to that of 'difference', but
404 appears as lower contrast. Painting with white inverts the
405 destination color. Painting with black produces no change.</td>
406 </tr>
407
408 <tr valign="top">
409 <td valign="top">darken</td>
410 <td valign="top">Selects the darker of the destination and source colors.
411 The destination is replaced with the source when the source is darker,
412 otherwise it is left unchanged.</td>
413 </tr>
414
415 <tr valign="top">
416 <td valign="top">lighten</td>
417 <td valign="top">Selects the lighter of the destination and source colors.
418 The destination is replaced with the source when the source is
419 lighter, otherwise it is left unchanged. </td>
420 </tr>
421
422 </tbody>
423</table>
424
425<p>Typically these use the default 'Over' alpha blending when transparencies
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]426are also involved, except for 'Plus' which uses a 'plus' alpha blending. This
427means the alpha channel of both images will only be used to ensure that any
428visible input remains visible even in parts not overlaid. It also means that
429any values are weighted by the alpha channel of the input and output images.
430This 'Over' alpha blending is also applied to the lighting composition methods
431below. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]432
433<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]434(enabled by default) with the <a href="../www/command-line-options.html#channel"
435>-channel</a> setting, then the above mathematical compositions will nolonger
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]436syncronise its actions with the alpha channel. Instead the math composition
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]437will be applied on an individual channel basis as defined by the <a
438href="../www/command-line-options.html#channel"
439>-channel</a>. This includes the alpha channel. This special usage
440allows you to perform true mathematics of the image channels, without alpha
441compostion effects, becomming involved. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]442
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]443<p>This special flag is not applied to the lighting composition methods (see
444below) even though they are closely related to mathematical composition
445methods.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]446
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]447<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]448
449<p>The following lighting composition methods are also available. </p>
450
451<table class="doc">
452 <tbody>
453 <tr valign="top">
454 <th align="left" style="width: 8%">Method</th>
455 <th align="left">Description</th>
456 </tr>
457
458 <tr valign="top">
459 <td valign="top">linear-dodge</td>
460 <td valign="top">This is equivelent to 'Plus' in that the color channels
461 are simply added, however it does not 'Plus' the alpha channel, but
462 uses the normal 'Over' alpha blending, which transparencies are
463 involved. Produces a sort of additive multiply-like result. Added
464 ImageMagick version 6.5.4-3. </td>
465 </tr>
466
467 <tr valign="top">
468 <td valign="top">linear-burn</td>
469 <td valign="top">As 'Linear-Dodge', but also subtract one from the result.
470 Sort of a additive 'Screen' of the images. Added ImageMagick version
471 6.5.4-3. </td>
472 </tr>
473
474 <tr valign="top">
475 <td valign="top">color-dodge</td>
476 <td valign="top">Brightens the destination color to reflect the source
477 color. Painting with black produces no change.</td>
478 </tr>
479
480 <tr valign="top">
481 <td valign="top">color-burn</td>
482 <td valign="top">Darkens the destination color to reflect the source
483 color. Painting with white produces no change. Fixed in ImageMagick
484 version 6.5.4-3. </td>
485 </tr>
486
487 <tr valign="top">
488 <td valign="top">overlay</td>
489 <td valign="top">Multiplies or screens the colors, dependent on the
490 destination color. Source colors overlay the destination whilst
491 preserving its highlights and shadows. The destination color is not
492 replaced, but is mixed with the source color to reflect the lightness
493 or darkness of the destination.</td>
494 </tr>
495
496 <tr valign="top">
497 <td valign="top">hard-light</td>
498 <td valign="top">Multiplies or screens the colors, dependent on the source
499 color value. If the source color is lighter than 0.5, the destination
500 is lightened as if it were screened. If the source color is darker
501 than 0.5, the destination is darkened, as if it were multiplied. The
502 degree of lightening or darkening is proportional to the difference
503 between the source color and 0.5. If it is equal to 0.5 the
504 destination is unchanged. Painting with pure black or white produces
505 black or white.</td>
506 </tr>
507
508
509 <tr valign="top">
510 <td valign="top">linear-light</td>
511 <td valign="top">Like 'Hard-Light' but using linear-dodge and linear-burn
512 instead. Increases contrast slightly with an impact on the
513 foreground's tonal values.</td>
514 </tr>
515
516 <tr valign="top">
517 <td valign="top">soft-light</td>
518 <td valign="top">Darkens or lightens the colors, dependent on the source
519 color value. If the source color is lighter than 0.5, the destination
520 is lightened. If the source color is darker than 0.5, the destination
521 is darkened, as if it were burned in. The degree of darkening or
522 lightening is proportional to the difference between the source color
523 and 0.5. If it is equal to 0.5, the destination is unchanged. Painting
524 with pure black or white produces a distinctly darker or lighter area,
525 but does not result in pure black or white. Fixed in ImageMagick
526 version 6.5.4-3. </td>
527 </tr>
528
529 <tr valign="top">
530 <td valign="top">pegtop-light</td>
531 <td valign="top">Almost equivelent to 'Soft-Light', but using a
532 continuious mathematical formula rather than two conditionally
533 selected formulae. Added ImageMagick version 6.5.4-3. </td>
534 </tr>
535
536 <tr valign="top">
537 <td valign="top">vivid-light</td>
538 <td valign="top">A modified 'Linear-Light' designed to preserve very stong
539 primary and secondary colors in the image. Added ImageMagick version
540 6.5.4-3. </td>
541 </tr>
542
543 <tr valign="top">
544 <td valign="top">pin-light</td>
545 <td valign="top">Similar to 'Hard-Light', but using sharp linear shadings,
546 to similate the effects of a strong 'pinhole' light source. Added
547 ImageMagick version 6.5.4-3. </td>
548 </tr>
549
550 </tbody>
551</table>
552
553
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]554<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]555
556<p>Also included are these special purpose compose methods:</p>
557
558<table class="doc">
559 <tbody>
560 <tr valign="top">
561 <th align="left" style="width: 8%">Method</th>
562 <th align="left">Description</th>
563 </tr>
564
565 <tr valign="top">
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]566 <td valign="top">copy</td>
567 <td valign="top">This is equivelent to the Duff-Porter composition method
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]568 '<kbd>Src,</kbd>' but without clearing the parts of the destination
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]569 image that is not overlaid. </td>
570 </tr>
571
572 <tr valign="top">
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]573 <td valign="top">copy-*</td>
574 <td valign="top">Copy the specified channel (Red, Green, Blue, Cyan,
575 Magenta, Yellow, Black, or Opacity) in the source image to the
576 same channel in the destination image. If the channel specified
577 does not exist in the source image, (which can only happen for methods,
578 '<kbd>copy-opacity</kbd>' or '<kbd>copy-black</kbd>') then it is
579 assumed that the source image is a special grayscale channel image
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]580 of the values that is to be copied. </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]581 </tr>
582
583 <tr valign="top">
584 <td valign="top">change-mask</td>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]585 <td valign="top">Replace any destination pixel that is the similar to the
586 source images pixel (as defined by the current <a
587 href="../www/command-line-options.html#fuzz">-fuzz</a> factor), with transparency.
588 </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]589 </tr>
590 </tbody>
591</table>
592
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]593<br><br>
594
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]595<p>On top of these composed methods are a few special ones that not only require
596the two images that are being merged or overlaid, but have some extra numerical
597arguments, which are tabled below. </p>
598
599<p>In the "<code>composite</code>" command these composition methods are
600selected using special options with the arguments needed. They are usually,
601but not always, the same name as the composte 'method' they use, and replaces
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]602the normal use of the <a href="../www/command-line-options.html#compose" >-compose</a>
603setting in the "<code>composite</code>" command. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]604
605<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>composite ... -blend 50x50 ...</span></p>
606<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]607these extra arguments to its <a href="../www/command-line-options.html#composite"
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]608>-composite</a> operator, using the special <a href="../www/command-line-options.html#define">-define</a>
609attribute of '<kbd class="arg">compose:args</kbd>'. This means you can now
610make use of these special argumented <a href="../www/command-line-options.html#compose"
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]611>-compose</a> methods, those the argument and the method both need to be set
612separatally. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]613
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]614<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]615<p>The following is a table of these special 'argumented' compose methods,
616with a brief summary of what they do. For more details see the equivalent
617"composite" command option name. </p>
618
619<table class="doc">
620 <tbody>
621 <tr valign="top">
622 <th align="left" style="width: 8%">Method</th>
623 <th align="left">Description</th>
624 </tr>
625
626 <tr valign="top">
627 <td valign="top">dissolve</td>
628 <td valign="top">Arguments:
629 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]630 <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]631 <br>Dissolve the 'source' image by the percentage given before overlaying
632 'over' the 'destination' image. If <em class="arg">src_percent</em> is
633 greater than 100, it starts dissolving the main image so it will
634 become transparent at a value of '<kbd class="arg">200</kbd>'. If
635 both percentages are given, each image are dissolved to the
636 percentages given.
637 </td>
638 </tr>
639
640 <tr valign="top">
641 <td valign="top">blend</td>
642 <td valign="top">Arguments:
643 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]644 <br>Equivalent to "<code>composite</code>" <a
645 href="../www/command-line-options.html#blend">-blend</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]646 <br>Average the images together ('plus') according to the percentages
647 given and each pixels transparency. If only a single percentage value
648 is given it sets the weight of the composite or 'source' image, while
649 the background image is weighted by the exact opposite amount. That is
650 a <kbd>-blend 30</kbd> merges 30% of the 'source' image with 70% of
651 the 'destination' image. Thus it is equivalent to <kbd>-blend
652 30x70</kbd>.
653 </td>
654 </tr>
655
656 <tr valign="top">
657 <td valign="top">mathematics</td>
658 <td valign="top">Arguments: <em class="arg">A, B, C, D</em>
659 <br>Not available in "<code>composite</code>" at this time.
660 <br>Merge the source and destination images according to the formula
661 <br>&nbsp; &nbsp; &nbsp;<code>A*Sc*Dc + B*Sc + C*Dc + D</code>
662 <br>Can be used to generate a custom composition method that would
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]663 otherwise need to be implemented using the slow <a
664 href="../www/command-line-options.html#fx">-fx</a> DIY image operator. Added
665 to ImageMagick version 6.5.4-3.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]666 <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]667 if the 'Sync' flag is removed from <a
668 href="../www/command-line-options.html#channel" >-channel</a>, just like all
669 the other mathematical compostion methods above.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]670 </td>
671 </tr>
672
673 <tr valign="top">
674 <td valign="top">modulate</td>
675 <td valign="top">Arguments:
676 <em class="arg">brightness</em>[x<em class="arg">saturation</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]677 <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]678 <br>Take a grayscale image (with alpha mask) and modify the destination
679 image's brightness according to watermark image's grayscale value and
680 the <em class="arg">brightness</em> percentage. The destinations
681 color saturation attribute is just direct modified by the <em
682 class="arg">saturation</em> percentage, which defaults to 100 percent
683 (no color change).
684
685 </td>
686 </tr>
687
688 <tr valign="top">
689 <td valign="top">displace</td>
690 <td valign="top">Arguments:
691 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em>][!][%]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]692 <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]693 <br>With this option, the 'overlay' image, and optionally the 'mask'
694 image, is used as a relative displacement map, which is used to
695 displace the lookup of what part of the destination image is seen at
696 each point of the overlaid area. Much like the displacement map is a
697 'lens' that distorts the original 'background' image behind it.
698 <br><br>
699 The X-scale is modilated by the 'red' channel of the overlay image
700 while the Y-scale is modulated by the green channel, (the mask image
701 if given is rolled into green channel of the overlay image. This
702 separation allows you to modulate the X and Y lookup displacement
703 separatally allowing you to di 2 dimentional displacements, rather
704 than 1 dimentional verctored displacements (using grayscale image).
705 <br><br>
706 If the overlay image contains transparency this is used as a mask
707 of the resulting image to remove 'invalid' pixels.
708 <br><br>
709 The '%' flag makes the displacement scale relative to the size of the
710 overlay image (100% = half width/height of image). Using '!' switches
711 percentage arguments to refer to the destination image size instead.
712 <br><br>
713 Special flags were added Added to ImageMagick version 6.5.3-5.
714 </td>
715 </tr>
716
717 <tr valign="top">
718 <td valign="top">distort</td>
719 <td valign="top">Arguments:
720 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em
721 >[+<em class="arg">X-center</em>+<em class="arg">Y-center</em>]][!][%]
722 <br>Not available in "<code>composite</code>" at this time.
723 <br>Exactly as per 'Displace' (above), but using absolute coordinates,
724 relative to the center of the overlay (or that given). Basically
725 allows you to generate absolute distortion maps where 'black' will
726 look up the left/top edge, and 'white' looks up the bottom/right
727 edge of the destination image, according to the scale given.
728 <br><br>
729 The '!' flag not only switches percentage scaling, to use the
730 destination image, but also the image the center offset of the lookup.
731 This means the overlay can lookup a completely different region of the
732 destination image.
733 <br><br>
734 Added to ImageMagick version 6.5.3-5.
735 </td>
736 </tr>
737
738 <tr valign="top">
739 <td valign="top">blur</td>
740 <td valign="top">Arguments:
741 <em class="arg">Width</em>[x<em class="arg">Height</em
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]742 >[+<em class="arg">Angle</em>][+<em class="arg">Angle2</em>]]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]743 <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]744 <br>A Variable Blur Mapping Composition method, where each pixel in the
745 overlaid region is replaced with an Elliptical Weighted Average (EWA),
746 with an ellipse (typically a circle) of the given sigma size, scaled
747 according to overlay (source image) grayscale mapping.
748 <br><br>
749 As per 'Displace' and 'Distort', the red channel will modulate the
750 width of the ellipse, while the green channel will modulate the height
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]751 of the ellipse. If a single Angle value is given in the arguments,
752 then the ellipse will then be rotated by the angle specifed.
753 <br><br>
754 Normally the blue channel of the mapping overlay image is ignored.
755 However if a second ellipse angle is given, then it is assumed that
756 the blue channel defines a variable angle for the ellipse ranging from
757 the first angle to the second angle given. This allows to generate
758 radial blurs, or a rough approximation for rotational blur. Or any mix
759 of the two.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]760 <br><br>
761 Added to ImageMagick version 6.5.4-0.
762 </td>
763 </tr>
764
765 </tbody>
766</table>
767
768<p>To print a complete list of all the available compose operators, use <a
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]769href="../www/command-line-options.html#list">-list compose</a>.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]770
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