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cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]172<p>This page descibed the Image composition methods that is used to define how
173two images should be merged together in various image operations. For the
174Command Line API it is typically set using the <A
175HREF="../www/command-line-options.html#compose" >-compose</A> setting option. </p>
176
177
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]178<p>The description of composition uses abstract terminology in order to allow
179the description to be more precise, while avoiding constant values which are
180specific to a particular build configuration. Each image pixel is represented
181by red, green, and blue levels (which are equal for a gray pixel). The
182build-dependent value <em class="QR">QuantumRange</em> is the maximum integral
183value which may be stored, per pixel, in the red, green, or blue channels of
184the image. Each image pixel may also optionally (if the image matte channel is
185enabled) have an associated level of opacity, ranging from <em>opaque</em> to
186<em>transparent</em>, which may be used to determine the influence of the pixel
187color when compositing the pixel with another image pixel. If the image matte
188channel is disabled, then all pixels in the image are treated as opaque. The
189color of an opaque pixel is fully visible while the color of a transparent
190pixel color is entirely absent (pixel color is ignored).</p>
191
192<p>By definition, raster images have a rectangular shape. All image rows are of
193equal length, as are all image columns. By treating the alpha channel as a
194visual "mask" the rectangular image may be given a "shape" by treating the
195alpha channel as a cookie-cutter for the image. This is done by setting the
196pixels within the shape to be opaque, with pixels outside the shape set as
197transparent. Pixels on the boundary of the shape may be between opaque and
198transparent in order to provide antialiasing (visually smooth edges). The
199description of the composition operators use this concept of image "shape" in
200order to make the description of the operators easier to understand. While it
201is convenient to describe the operators in terms of "shapes" they are by no
202means limited to mask-style operations since they are based on continuous
203floating-point mathematics rather than simple boolean operations.</p>
204
205<p>The following alpha blending (Duff-Porter) compose methods are available:</p>
206
207<table class="doc">
208 <tbody>
209 <tr valign="top">
210 <th align="left" style="width: 8%">Method</th>
211 <th align="left">Description</th>
212 </tr>
213
214 <tr valign="top">
215 <td valign="top">clear</td>
216 <td valign="top">Both the color and the alpha of the destination are
217 cleared. Neither the source nor the destination are used (except for
218 destinations size and other meta-data which is always preserved.</td>
219 </tr>
220
221 <tr valign="top">
222 <td valign="top">src</td>
223 <td valign="top">The source is copied to the destination. The destination
224 is not used as input, though it is cleared.</td>
225 </tr>
226
227 <tr valign="top">
228 <td valign="top">dst</td>
229 <td valign="top">The destination is left untouched. The source image is
230 completely ignored.</td>
231 </tr>
232
233 <tr valign="top">
234 <td valign="top">src-over</td>
235 <td valign="top">The source is composited over the destination. this is
236 the default alpha blending compose method, when neither the compose
237 setting is set, nor is set in the image meta-data.</td>
238 </tr>
239
240 <tr valign="top">
241 <td valign="top">dst-over</td>
242 <td valign="top">The destination is composited over the source and the
243 result replaces the destination.</td>
244 </tr>
245
246 <tr valign="top">
247 <td valign="top">src-in</td>
248 <td valign="top">The part of the source lying inside of the destination
249 replaces the destination.</td>
250 </tr>
251
252 <tr valign="top">
253 <td valign="top">dst-in</td>
254 <td valign="top">The part of the destination lying inside of the source
255 replaces the destination. Areas not overlaid are cleared.</td>
256 </tr>
257
258 <tr valign="top">
259 <td valign="top">src-out</td>
260 <td valign="top">The part of the source lying outside of the destination
261 replaces the destination.</td>
262 </tr>
263
264 <tr valign="top">
265 <td valign="top">dst-out</td>
266 <td valign="top">The part of the destination lying outside of the source
267 replaces the destination.</td>
268 </tr>
269
270 <tr valign="top">
271 <td valign="top">src-atop</td>
272 <td valign="top">The part of the source lying inside of the destination is
273 composited onto the destination.</td>
274 </tr>
275
276 <tr valign="top">
277 <td valign="top">dst-atop</td>
278 <td valign="top">The part of the destination lying inside of the source is
279 composited over the source and replaces the destination. Areas not
280 overlaid are cleared. </td>
281 </tr>
282
283 <tr valign="top">
284 <td valign="top">xor</td>
285 <td valign="top">The part of the source that lies outside of the
286 destination is combined with the part of the destination that lies
287 outside of the source. Source or Destination, but not both. </td>
288 </tr>
289
290 </tbody>
291</table>
292
293<p>Any of the 'Src-*' methods can also be specified without the 'Src-' part.
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]294For example the default compose method can be specified as just 'Over'.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]295
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]296<p>Many of these compose methods will clear the destination image which was
297not overlaid by the source image. This is to be expected as part of that
298specific composition methods defintion. Seeing the You can disable this by
299setting the special <A HREF="../www/command-line-options.html#set" >-set</A>
300'option:compose:outside-overlay' to 'false' will turn off this behaviour. </p>
301
302<p>On top of the above 12 Duff-Porter Alpha Composition methods, one special
303related method '<kbd>Copy</kbd>' has been provided. This is equivelent to the
304'<kbd>Src</kbd>' with the special <A HREF="../www/command-line-options.html#set"
305>-set</A> option '<kbd>option:compose:outside-overlay</kbd>' set to
306'<kbd>false></kbd>'. </p>
307
308<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]309
310<p>The following mathemathical composition methods are also available. </p>
311
312<table class="doc">
313 <tbody>
314 <tr valign="top">
315 <th align="left" style="width: 8%">Method</th>
316 <th align="left">Description</th>
317 </tr>
318
319 <tr valign="top">
320 <td valign="top">multiply</td>
321 <td valign="top">The source is multiplied by the destination and replaces
322 the destination. The resultant color is always at least as dark as
323 either of the two constituent colors. Multiplying any color with black
324 produces black. Multiplying any color with white leaves the original
325 color unchanged.</td>
326 </tr>
327
328 <tr valign="top">
329 <td valign="top">screen</td>
330 <td valign="top">The source and destination are complemented and then
331 multiplied and then replace the destination. The resultant color is
332 always at least as light as either of the two constituent colors.
333 Screening any color with white produces white. Screening any color
334 with black leaves the original color unchanged.</td>
335 </tr>
336
337 <tr valign="top">
338 <td valign="top">plus</td>
339 <td valign="top">The source is added to the destination and replaces the
340 destination. This operator is useful for averaging or a controled
341 merger of two images, rather than a direct overlay.</td>
342 </tr>
343
344 <tr valign="top">
345 <td valign="top">add</td>
346 <td valign="top">As per 'plus' but transparency data is treated as matte
347 values. As such any transparent areas in either image remain
348 transparent. </td>
349 </tr>
350
351 <tr valign="top">
352 <td valign="top">minus</td>
353 <td valign="top">Subtract the colors in the source image from the
354 destination image. When transparency is involved, opaque areas is
355 subtracted from any destination opaque areas. </td>
356 </tr>
357
358 <tr valign="top">
359 <td valign="top">subtract</td>
360 <td valign="top">Subtract the colors in the source image from the
361 destination image. When transparency is involved transparent areas are
362 subtracted, so only the opaque areas in the source remain opaque in
363 the destination image. </td>
364 </tr>
365
366 <tr valign="top">
367 <td valign="top">difference</td>
368 <td valign="top">Subtracts the darker of the two constituent colors from
369 the lighter. Painting with white inverts the destination color.
370 Painting with black produces no change.</td>
371 </tr>
372
373 <tr valign="top">
374 <td valign="top">exclusion</td>
375 <td valign="top">Produces an effect similar to that of 'difference', but
376 appears as lower contrast. Painting with white inverts the
377 destination color. Painting with black produces no change.</td>
378 </tr>
379
380 <tr valign="top">
381 <td valign="top">darken</td>
382 <td valign="top">Selects the darker of the destination and source colors.
383 The destination is replaced with the source when the source is darker,
384 otherwise it is left unchanged.</td>
385 </tr>
386
387 <tr valign="top">
388 <td valign="top">lighten</td>
389 <td valign="top">Selects the lighter of the destination and source colors.
390 The destination is replaced with the source when the source is
391 lighter, otherwise it is left unchanged. </td>
392 </tr>
393
394 </tbody>
395</table>
396
397<p>Typically these use the default 'Over' alpha blending when transparencies
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]398are also involved, except for 'Plus' which uses a 'plus' alpha blending. This
399means the alpha channel of both images will only be used to ensure that any
400visible input remains visible even in parts not overlaid. It also means that
401any values are weighted by the alpha channel of the input and output images.
402This 'Over' alpha blending is also applied to the lighting composition methods
403below. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]404
405<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]406(enabled by default) with the <a href="../www/command-line-options.html#channel"
407>-channel</a> setting, then the above mathematical compositions will nolonger
408syncronise its actiosn with the alpha channel. Instead the math composition
409will be applied on an individual channel basis as defined by the <a
410href="../www/command-line-options.html#channel"
411>-channel</a>. This includes the alpha channel. This special usage
412allows you to perform true mathematics of the image channels, without alpha
413compostion effects, becomming involved. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]414
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]415<p>This special flag is not applied to the lighting composition methods (see
416below) even though they are closely related to mathematical composition
417methods.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]418
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]419<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]420
421<p>The following lighting composition methods are also available. </p>
422
423<table class="doc">
424 <tbody>
425 <tr valign="top">
426 <th align="left" style="width: 8%">Method</th>
427 <th align="left">Description</th>
428 </tr>
429
430 <tr valign="top">
431 <td valign="top">linear-dodge</td>
432 <td valign="top">This is equivelent to 'Plus' in that the color channels
433 are simply added, however it does not 'Plus' the alpha channel, but
434 uses the normal 'Over' alpha blending, which transparencies are
435 involved. Produces a sort of additive multiply-like result. Added
436 ImageMagick version 6.5.4-3. </td>
437 </tr>
438
439 <tr valign="top">
440 <td valign="top">linear-burn</td>
441 <td valign="top">As 'Linear-Dodge', but also subtract one from the result.
442 Sort of a additive 'Screen' of the images. Added ImageMagick version
443 6.5.4-3. </td>
444 </tr>
445
446 <tr valign="top">
447 <td valign="top">color-dodge</td>
448 <td valign="top">Brightens the destination color to reflect the source
449 color. Painting with black produces no change.</td>
450 </tr>
451
452 <tr valign="top">
453 <td valign="top">color-burn</td>
454 <td valign="top">Darkens the destination color to reflect the source
455 color. Painting with white produces no change. Fixed in ImageMagick
456 version 6.5.4-3. </td>
457 </tr>
458
459 <tr valign="top">
460 <td valign="top">overlay</td>
461 <td valign="top">Multiplies or screens the colors, dependent on the
462 destination color. Source colors overlay the destination whilst
463 preserving its highlights and shadows. The destination color is not
464 replaced, but is mixed with the source color to reflect the lightness
465 or darkness of the destination.</td>
466 </tr>
467
468 <tr valign="top">
469 <td valign="top">hard-light</td>
470 <td valign="top">Multiplies or screens the colors, dependent on the source
471 color value. If the source color is lighter than 0.5, the destination
472 is lightened as if it were screened. If the source color is darker
473 than 0.5, the destination is darkened, as if it were multiplied. The
474 degree of lightening or darkening is proportional to the difference
475 between the source color and 0.5. If it is equal to 0.5 the
476 destination is unchanged. Painting with pure black or white produces
477 black or white.</td>
478 </tr>
479
480
481 <tr valign="top">
482 <td valign="top">linear-light</td>
483 <td valign="top">Like 'Hard-Light' but using linear-dodge and linear-burn
484 instead. Increases contrast slightly with an impact on the
485 foreground's tonal values.</td>
486 </tr>
487
488 <tr valign="top">
489 <td valign="top">soft-light</td>
490 <td valign="top">Darkens or lightens the colors, dependent on the source
491 color value. If the source color is lighter than 0.5, the destination
492 is lightened. If the source color is darker than 0.5, the destination
493 is darkened, as if it were burned in. The degree of darkening or
494 lightening is proportional to the difference between the source color
495 and 0.5. If it is equal to 0.5, the destination is unchanged. Painting
496 with pure black or white produces a distinctly darker or lighter area,
497 but does not result in pure black or white. Fixed in ImageMagick
498 version 6.5.4-3. </td>
499 </tr>
500
501 <tr valign="top">
502 <td valign="top">pegtop-light</td>
503 <td valign="top">Almost equivelent to 'Soft-Light', but using a
504 continuious mathematical formula rather than two conditionally
505 selected formulae. Added ImageMagick version 6.5.4-3. </td>
506 </tr>
507
508 <tr valign="top">
509 <td valign="top">vivid-light</td>
510 <td valign="top">A modified 'Linear-Light' designed to preserve very stong
511 primary and secondary colors in the image. Added ImageMagick version
512 6.5.4-3. </td>
513 </tr>
514
515 <tr valign="top">
516 <td valign="top">pin-light</td>
517 <td valign="top">Similar to 'Hard-Light', but using sharp linear shadings,
518 to similate the effects of a strong 'pinhole' light source. Added
519 ImageMagick version 6.5.4-3. </td>
520 </tr>
521
522 </tbody>
523</table>
524
525
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]526<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]527
528<p>Also included are these special purpose compose methods:</p>
529
530<table class="doc">
531 <tbody>
532 <tr valign="top">
533 <th align="left" style="width: 8%">Method</th>
534 <th align="left">Description</th>
535 </tr>
536
537 <tr valign="top">
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]538 <td valign="top">copy</td>
539 <td valign="top">This is equivelent to the Duff-Porter composition method
540 '<kbd>Src,<kbd>' but withotu clearing the parts of the destination
541 image that is not overlaid. </td>
542 </tr>
543
544 <tr valign="top">
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]545 <td valign="top">copy-*</td>
546 <td valign="top">Copy the specified channel (Red, Green, Blue, Cyan,
547 Magenta, Yellow, Black, or Opacity) in the source image to the
548 same channel in the destination image. If the channel specified
549 does not exist in the source image, (which can only happen for methods,
550 '<kbd>copy-opacity</kbd>' or '<kbd>copy-black</kbd>') then it is
551 assumed that the source image is a special grayscale channel image
552 of the values to be copied. </td>
553 </tr>
554
555 <tr valign="top">
556 <td valign="top">change-mask</td>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]557 <td valign="top">Replace any destination pixel that is the similar to the
558 source images pixel (as defined by the current <a
559 href="../www/command-line-options.html#fuzz">-fuzz</a> factor), with transparency.
560 </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]561 </tr>
562 </tbody>
563</table>
564
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]565<br><br>
566
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]567<p>On top of these composed methods are a few special ones that not only require
568the two images that are being merged or overlaid, but have some extra numerical
569arguments, which are tabled below. </p>
570
571<p>In the "<code>composite</code>" command these composition methods are
572selected using special options with the arguments needed. They are usually,
573but not always, the same name as the composte 'method' they use, and replaces
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]574the normal use of the <a href="../www/command-line-options.html#compose" >-compose</a>
575setting in the "<code>composite</code>" command. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]576
577<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>composite ... -blend 50x50 ...</span></p>
578<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]579these extra arguments to its <a href="../www/command-line-options.html#composite"
580>-composite</a> operator, using the special <a
581href="../www/command-line-options.html#set">-set</a> attribute of '<kbd
582class="arg">option:compose:args</kbd>'. This means you can now make use of
583these special argumented <a href="../www/command-line-options.html#compose"
584>-compose</a> methods, those the argument and the method both need to be set
585separatally. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]586
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]587<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>convert ... -compose blend -set option:compose:args 50x50 -composite ...</span></p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]588<p>The following is a table of these special 'argumented' compose methods,
589with a brief summary of what they do. For more details see the equivalent
590"composite" command option name. </p>
591
592<table class="doc">
593 <tbody>
594 <tr valign="top">
595 <th align="left" style="width: 8%">Method</th>
596 <th align="left">Description</th>
597 </tr>
598
599 <tr valign="top">
600 <td valign="top">dissolve</td>
601 <td valign="top">Arguments:
602 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]603 <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]604 <br>Dissolve the 'source' image by the percentage given before overlaying
605 'over' the 'destination' image. If <em class="arg">src_percent</em> is
606 greater than 100, it starts dissolving the main image so it will
607 become transparent at a value of '<kbd class="arg">200</kbd>'. If
608 both percentages are given, each image are dissolved to the
609 percentages given.
610 </td>
611 </tr>
612
613 <tr valign="top">
614 <td valign="top">blend</td>
615 <td valign="top">Arguments:
616 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]617 <br>Equivalent to "<code>composite</code>" <a
618 href="../www/command-line-options.html#blend">-blend</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]619 <br>Average the images together ('plus') according to the percentages
620 given and each pixels transparency. If only a single percentage value
621 is given it sets the weight of the composite or 'source' image, while
622 the background image is weighted by the exact opposite amount. That is
623 a <kbd>-blend 30</kbd> merges 30% of the 'source' image with 70% of
624 the 'destination' image. Thus it is equivalent to <kbd>-blend
625 30x70</kbd>.
626 </td>
627 </tr>
628
629 <tr valign="top">
630 <td valign="top">mathematics</td>
631 <td valign="top">Arguments: <em class="arg">A, B, C, D</em>
632 <br>Not available in "<code>composite</code>" at this time.
633 <br>Merge the source and destination images according to the formula
634 <br>&nbsp; &nbsp; &nbsp;<code>A*Sc*Dc + B*Sc + C*Dc + D</code>
635 <br>Can be used to generate a custom composition method that would
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]636 otherwise need to be implemented using the slow <a
637 href="../www/command-line-options.html#fx">-fx</a> DIY image operator. Added
638 to ImageMagick version 6.5.4-3.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]639 <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]640 if the 'Sync' flag is removed from <a
641 href="../www/command-line-options.html#channel" >-channel</a>, just like all
642 the other mathematical compostion methods above.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]643 </td>
644 </tr>
645
646 <tr valign="top">
647 <td valign="top">modulate</td>
648 <td valign="top">Arguments:
649 <em class="arg">brightness</em>[x<em class="arg">saturation</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]650 <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]651 <br>Take a grayscale image (with alpha mask) and modify the destination
652 image's brightness according to watermark image's grayscale value and
653 the <em class="arg">brightness</em> percentage. The destinations
654 color saturation attribute is just direct modified by the <em
655 class="arg">saturation</em> percentage, which defaults to 100 percent
656 (no color change).
657
658 </td>
659 </tr>
660
661 <tr valign="top">
662 <td valign="top">displace</td>
663 <td valign="top">Arguments:
664 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em>][!][%]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]665 <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]666 <br>With this option, the 'overlay' image, and optionally the 'mask'
667 image, is used as a relative displacement map, which is used to
668 displace the lookup of what part of the destination image is seen at
669 each point of the overlaid area. Much like the displacement map is a
670 'lens' that distorts the original 'background' image behind it.
671 <br><br>
672 The X-scale is modilated by the 'red' channel of the overlay image
673 while the Y-scale is modulated by the green channel, (the mask image
674 if given is rolled into green channel of the overlay image. This
675 separation allows you to modulate the X and Y lookup displacement
676 separatally allowing you to di 2 dimentional displacements, rather
677 than 1 dimentional verctored displacements (using grayscale image).
678 <br><br>
679 If the overlay image contains transparency this is used as a mask
680 of the resulting image to remove 'invalid' pixels.
681 <br><br>
682 The '%' flag makes the displacement scale relative to the size of the
683 overlay image (100% = half width/height of image). Using '!' switches
684 percentage arguments to refer to the destination image size instead.
685 <br><br>
686 Special flags were added Added to ImageMagick version 6.5.3-5.
687 </td>
688 </tr>
689
690 <tr valign="top">
691 <td valign="top">distort</td>
692 <td valign="top">Arguments:
693 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em
694 >[+<em class="arg">X-center</em>+<em class="arg">Y-center</em>]][!][%]
695 <br>Not available in "<code>composite</code>" at this time.
696 <br>Exactly as per 'Displace' (above), but using absolute coordinates,
697 relative to the center of the overlay (or that given). Basically
698 allows you to generate absolute distortion maps where 'black' will
699 look up the left/top edge, and 'white' looks up the bottom/right
700 edge of the destination image, according to the scale given.
701 <br><br>
702 The '!' flag not only switches percentage scaling, to use the
703 destination image, but also the image the center offset of the lookup.
704 This means the overlay can lookup a completely different region of the
705 destination image.
706 <br><br>
707 Added to ImageMagick version 6.5.3-5.
708 </td>
709 </tr>
710
711 <tr valign="top">
712 <td valign="top">blur</td>
713 <td valign="top">Arguments:
714 <em class="arg">Width</em>[x<em class="arg">Height</em
715 >[+<em class="arg">Angle</em>]]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]716 <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]717 <br>A Variable Blur Mapping Composition method, where each pixel in the
718 overlaid region is replaced with an Elliptical Weighted Average (EWA),
719 with an ellipse (typically a circle) of the given sigma size, scaled
720 according to overlay (source image) grayscale mapping.
721 <br><br>
722 As per 'Displace' and 'Distort', the red channel will modulate the
723 width of the ellipse, while the green channel will modulate the height
724 of the ellipse. However at this time the ellipse angle is not
725 modulated though this may be a future posibility (perhaps with a
726 special flag to enable use of blur channel for this purpose).
727 <br><br>
728 Added to ImageMagick version 6.5.4-0.
729 </td>
730 </tr>
731
732 </tbody>
733</table>
734
735<p>To print a complete list of all the available compose operators, use <a
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]736href="../www/command-line-options.html#list">-list compose</a>.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]737
738
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