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cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]178<h1>ImageMagick Image Composition</h1>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]179<p>This page descibed the Image composition methods that is used to define how
180two images should be merged together in various image operations. For the
181Command Line API it is typically set using the <A
182HREF="../www/command-line-options.html#compose" >-compose</A> setting option. </p>
183
184
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]185<p>The description of composition uses abstract terminology in order to allow
186the description to be more precise, while avoiding constant values which are
187specific to a particular build configuration. Each image pixel is represented
188by red, green, and blue levels (which are equal for a gray pixel). The
189build-dependent value <em class="QR">QuantumRange</em> is the maximum integral
190value which may be stored, per pixel, in the red, green, or blue channels of
191the image. Each image pixel may also optionally (if the image matte channel is
192enabled) have an associated level of opacity, ranging from <em>opaque</em> to
193<em>transparent</em>, which may be used to determine the influence of the pixel
194color when compositing the pixel with another image pixel. If the image matte
195channel is disabled, then all pixels in the image are treated as opaque. The
196color of an opaque pixel is fully visible while the color of a transparent
197pixel color is entirely absent (pixel color is ignored).</p>
198
199<p>By definition, raster images have a rectangular shape. All image rows are of
200equal length, as are all image columns. By treating the alpha channel as a
201visual "mask" the rectangular image may be given a "shape" by treating the
202alpha channel as a cookie-cutter for the image. This is done by setting the
203pixels within the shape to be opaque, with pixels outside the shape set as
204transparent. Pixels on the boundary of the shape may be between opaque and
205transparent in order to provide antialiasing (visually smooth edges). The
206description of the composition operators use this concept of image "shape" in
207order to make the description of the operators easier to understand. While it
208is convenient to describe the operators in terms of "shapes" they are by no
209means limited to mask-style operations since they are based on continuous
210floating-point mathematics rather than simple boolean operations.</p>
211
212<p>The following alpha blending (Duff-Porter) compose methods are available:</p>
213
214<table class="doc">
215 <tbody>
216 <tr valign="top">
217 <th align="left" style="width: 8%">Method</th>
218 <th align="left">Description</th>
219 </tr>
220
221 <tr valign="top">
222 <td valign="top">clear</td>
223 <td valign="top">Both the color and the alpha of the destination are
224 cleared. Neither the source nor the destination are used (except for
225 destinations size and other meta-data which is always preserved.</td>
226 </tr>
227
228 <tr valign="top">
229 <td valign="top">src</td>
230 <td valign="top">The source is copied to the destination. The destination
231 is not used as input, though it is cleared.</td>
232 </tr>
233
234 <tr valign="top">
235 <td valign="top">dst</td>
236 <td valign="top">The destination is left untouched. The source image is
237 completely ignored.</td>
238 </tr>
239
240 <tr valign="top">
241 <td valign="top">src-over</td>
242 <td valign="top">The source is composited over the destination. this is
243 the default alpha blending compose method, when neither the compose
244 setting is set, nor is set in the image meta-data.</td>
245 </tr>
246
247 <tr valign="top">
248 <td valign="top">dst-over</td>
249 <td valign="top">The destination is composited over the source and the
250 result replaces the destination.</td>
251 </tr>
252
253 <tr valign="top">
254 <td valign="top">src-in</td>
255 <td valign="top">The part of the source lying inside of the destination
256 replaces the destination.</td>
257 </tr>
258
259 <tr valign="top">
260 <td valign="top">dst-in</td>
261 <td valign="top">The part of the destination lying inside of the source
262 replaces the destination. Areas not overlaid are cleared.</td>
263 </tr>
264
265 <tr valign="top">
266 <td valign="top">src-out</td>
267 <td valign="top">The part of the source lying outside of the destination
268 replaces the destination.</td>
269 </tr>
270
271 <tr valign="top">
272 <td valign="top">dst-out</td>
273 <td valign="top">The part of the destination lying outside of the source
274 replaces the destination.</td>
275 </tr>
276
277 <tr valign="top">
278 <td valign="top">src-atop</td>
279 <td valign="top">The part of the source lying inside of the destination is
280 composited onto the destination.</td>
281 </tr>
282
283 <tr valign="top">
284 <td valign="top">dst-atop</td>
285 <td valign="top">The part of the destination lying inside of the source is
286 composited over the source and replaces the destination. Areas not
287 overlaid are cleared. </td>
288 </tr>
289
290 <tr valign="top">
291 <td valign="top">xor</td>
292 <td valign="top">The part of the source that lies outside of the
293 destination is combined with the part of the destination that lies
294 outside of the source. Source or Destination, but not both. </td>
295 </tr>
296
297 </tbody>
298</table>
299
300<p>Any of the 'Src-*' methods can also be specified without the 'Src-' part.
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]301For example the default compose method can be specified as just 'Over'.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]302
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]303<p>Many of these compose methods will clear the destination image which was
304not overlaid by the source image. This is to be expected as part of that
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]305specific composition methods defintion. You can disable this by setting the
306special <A HREF="../www/command-line-options.html#define"
307>-define</A> 'compose:outside-overlay' to a value of 'false' will turn off
308this behaviour. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]309
310<p>On top of the above 12 Duff-Porter Alpha Composition methods, one special
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]311related method '<kbd>Copy</kbd>' has been provided. This is equivelent to
312using the '<kbd>Src</kbd>' with the special <A HREF="../www/command-line-options.html#define"
313>-define</A> option '<kbd>compose:outside-overlay</kbd>' set to
314'<kbd>false</kbd>', so as to only modify the overlaid area, without clearing
315the rest of the image outside the overlaid area. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]316
317<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]318
319<p>The following mathemathical composition methods are also available. </p>
320
321<table class="doc">
322 <tbody>
323 <tr valign="top">
324 <th align="left" style="width: 8%">Method</th>
325 <th align="left">Description</th>
326 </tr>
327
328 <tr valign="top">
329 <td valign="top">multiply</td>
330 <td valign="top">The source is multiplied by the destination and replaces
331 the destination. The resultant color is always at least as dark as
332 either of the two constituent colors. Multiplying any color with black
333 produces black. Multiplying any color with white leaves the original
334 color unchanged.</td>
335 </tr>
336
337 <tr valign="top">
338 <td valign="top">screen</td>
339 <td valign="top">The source and destination are complemented and then
340 multiplied and then replace the destination. The resultant color is
341 always at least as light as either of the two constituent colors.
342 Screening any color with white produces white. Screening any color
343 with black leaves the original color unchanged.</td>
344 </tr>
345
346 <tr valign="top">
347 <td valign="top">plus</td>
348 <td valign="top">The source is added to the destination and replaces the
349 destination. This operator is useful for averaging or a controled
350 merger of two images, rather than a direct overlay.</td>
351 </tr>
352
353 <tr valign="top">
354 <td valign="top">add</td>
355 <td valign="top">As per 'plus' but transparency data is treated as matte
356 values. As such any transparent areas in either image remain
357 transparent. </td>
358 </tr>
359
360 <tr valign="top">
361 <td valign="top">minus</td>
362 <td valign="top">Subtract the colors in the source image from the
363 destination image. When transparency is involved, opaque areas is
364 subtracted from any destination opaque areas. </td>
365 </tr>
366
367 <tr valign="top">
368 <td valign="top">subtract</td>
369 <td valign="top">Subtract the colors in the source image from the
370 destination image. When transparency is involved transparent areas are
371 subtracted, so only the opaque areas in the source remain opaque in
372 the destination image. </td>
373 </tr>
374
375 <tr valign="top">
376 <td valign="top">difference</td>
377 <td valign="top">Subtracts the darker of the two constituent colors from
378 the lighter. Painting with white inverts the destination color.
379 Painting with black produces no change.</td>
380 </tr>
381
382 <tr valign="top">
383 <td valign="top">exclusion</td>
384 <td valign="top">Produces an effect similar to that of 'difference', but
385 appears as lower contrast. Painting with white inverts the
386 destination color. Painting with black produces no change.</td>
387 </tr>
388
389 <tr valign="top">
390 <td valign="top">darken</td>
391 <td valign="top">Selects the darker of the destination and source colors.
392 The destination is replaced with the source when the source is darker,
393 otherwise it is left unchanged.</td>
394 </tr>
395
396 <tr valign="top">
397 <td valign="top">lighten</td>
398 <td valign="top">Selects the lighter of the destination and source colors.
399 The destination is replaced with the source when the source is
400 lighter, otherwise it is left unchanged. </td>
401 </tr>
402
403 </tbody>
404</table>
405
406<p>Typically these use the default 'Over' alpha blending when transparencies
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]407are also involved, except for 'Plus' which uses a 'plus' alpha blending. This
408means the alpha channel of both images will only be used to ensure that any
409visible input remains visible even in parts not overlaid. It also means that
410any values are weighted by the alpha channel of the input and output images.
411This 'Over' alpha blending is also applied to the lighting composition methods
412below. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]413
414<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]415(enabled by default) with the <a href="../www/command-line-options.html#channel"
416>-channel</a> setting, then the above mathematical compositions will nolonger
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]417syncronise its actions with the alpha channel. Instead the math composition
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]418will be applied on an individual channel basis as defined by the <a
419href="../www/command-line-options.html#channel"
420>-channel</a>. This includes the alpha channel. This special usage
421allows you to perform true mathematics of the image channels, without alpha
422compostion effects, becomming involved. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]423
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]424<p>This special flag is not applied to the lighting composition methods (see
425below) even though they are closely related to mathematical composition
426methods.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]427
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]428<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]429
430<p>The following lighting composition methods are also available. </p>
431
432<table class="doc">
433 <tbody>
434 <tr valign="top">
435 <th align="left" style="width: 8%">Method</th>
436 <th align="left">Description</th>
437 </tr>
438
439 <tr valign="top">
440 <td valign="top">linear-dodge</td>
441 <td valign="top">This is equivelent to 'Plus' in that the color channels
442 are simply added, however it does not 'Plus' the alpha channel, but
443 uses the normal 'Over' alpha blending, which transparencies are
444 involved. Produces a sort of additive multiply-like result. Added
445 ImageMagick version 6.5.4-3. </td>
446 </tr>
447
448 <tr valign="top">
449 <td valign="top">linear-burn</td>
450 <td valign="top">As 'Linear-Dodge', but also subtract one from the result.
451 Sort of a additive 'Screen' of the images. Added ImageMagick version
452 6.5.4-3. </td>
453 </tr>
454
455 <tr valign="top">
456 <td valign="top">color-dodge</td>
457 <td valign="top">Brightens the destination color to reflect the source
458 color. Painting with black produces no change.</td>
459 </tr>
460
461 <tr valign="top">
462 <td valign="top">color-burn</td>
463 <td valign="top">Darkens the destination color to reflect the source
464 color. Painting with white produces no change. Fixed in ImageMagick
465 version 6.5.4-3. </td>
466 </tr>
467
468 <tr valign="top">
469 <td valign="top">overlay</td>
470 <td valign="top">Multiplies or screens the colors, dependent on the
471 destination color. Source colors overlay the destination whilst
472 preserving its highlights and shadows. The destination color is not
473 replaced, but is mixed with the source color to reflect the lightness
474 or darkness of the destination.</td>
475 </tr>
476
477 <tr valign="top">
478 <td valign="top">hard-light</td>
479 <td valign="top">Multiplies or screens the colors, dependent on the source
480 color value. If the source color is lighter than 0.5, the destination
481 is lightened as if it were screened. If the source color is darker
482 than 0.5, the destination is darkened, as if it were multiplied. The
483 degree of lightening or darkening is proportional to the difference
484 between the source color and 0.5. If it is equal to 0.5 the
485 destination is unchanged. Painting with pure black or white produces
486 black or white.</td>
487 </tr>
488
489
490 <tr valign="top">
491 <td valign="top">linear-light</td>
492 <td valign="top">Like 'Hard-Light' but using linear-dodge and linear-burn
493 instead. Increases contrast slightly with an impact on the
494 foreground's tonal values.</td>
495 </tr>
496
497 <tr valign="top">
498 <td valign="top">soft-light</td>
499 <td valign="top">Darkens or lightens the colors, dependent on the source
500 color value. If the source color is lighter than 0.5, the destination
501 is lightened. If the source color is darker than 0.5, the destination
502 is darkened, as if it were burned in. The degree of darkening or
503 lightening is proportional to the difference between the source color
504 and 0.5. If it is equal to 0.5, the destination is unchanged. Painting
505 with pure black or white produces a distinctly darker or lighter area,
506 but does not result in pure black or white. Fixed in ImageMagick
507 version 6.5.4-3. </td>
508 </tr>
509
510 <tr valign="top">
511 <td valign="top">pegtop-light</td>
512 <td valign="top">Almost equivelent to 'Soft-Light', but using a
513 continuious mathematical formula rather than two conditionally
514 selected formulae. Added ImageMagick version 6.5.4-3. </td>
515 </tr>
516
517 <tr valign="top">
518 <td valign="top">vivid-light</td>
519 <td valign="top">A modified 'Linear-Light' designed to preserve very stong
520 primary and secondary colors in the image. Added ImageMagick version
521 6.5.4-3. </td>
522 </tr>
523
524 <tr valign="top">
525 <td valign="top">pin-light</td>
526 <td valign="top">Similar to 'Hard-Light', but using sharp linear shadings,
527 to similate the effects of a strong 'pinhole' light source. Added
528 ImageMagick version 6.5.4-3. </td>
529 </tr>
530
531 </tbody>
532</table>
533
534
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]535<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]536
537<p>Also included are these special purpose compose methods:</p>
538
539<table class="doc">
540 <tbody>
541 <tr valign="top">
542 <th align="left" style="width: 8%">Method</th>
543 <th align="left">Description</th>
544 </tr>
545
546 <tr valign="top">
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]547 <td valign="top">copy</td>
548 <td valign="top">This is equivelent to the Duff-Porter composition method
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]549 '<kbd>Src,</kbd>' but without clearing the parts of the destination
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]550 image that is not overlaid. </td>
551 </tr>
552
553 <tr valign="top">
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]554 <td valign="top">copy-*</td>
555 <td valign="top">Copy the specified channel (Red, Green, Blue, Cyan,
556 Magenta, Yellow, Black, or Opacity) in the source image to the
557 same channel in the destination image. If the channel specified
558 does not exist in the source image, (which can only happen for methods,
559 '<kbd>copy-opacity</kbd>' or '<kbd>copy-black</kbd>') then it is
560 assumed that the source image is a special grayscale channel image
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]561 of the values that is to be copied. </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]562 </tr>
563
564 <tr valign="top">
565 <td valign="top">change-mask</td>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]566 <td valign="top">Replace any destination pixel that is the similar to the
567 source images pixel (as defined by the current <a
568 href="../www/command-line-options.html#fuzz">-fuzz</a> factor), with transparency.
569 </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]570 </tr>
571 </tbody>
572</table>
573
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]574<br><br>
575
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]576<p>On top of these composed methods are a few special ones that not only require
577the two images that are being merged or overlaid, but have some extra numerical
578arguments, which are tabled below. </p>
579
580<p>In the "<code>composite</code>" command these composition methods are
581selected using special options with the arguments needed. They are usually,
582but not always, the same name as the composte 'method' they use, and replaces
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]583the normal use of the <a href="../www/command-line-options.html#compose" >-compose</a>
584setting in the "<code>composite</code>" command. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]585
586<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>composite ... -blend 50x50 ...</span></p>
587<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]588these extra arguments to its <a href="../www/command-line-options.html#composite"
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]589>-composite</a> operator, using the special <a href="../www/command-line-options.html#define">-define</a>
590attribute of '<kbd class="arg">compose:args</kbd>'. This means you can now
591make use of these special argumented <a href="../www/command-line-options.html#compose"
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]592>-compose</a> methods, those the argument and the method both need to be set
593separatally. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]594
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]595<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]596<p>The following is a table of these special 'argumented' compose methods,
597with a brief summary of what they do. For more details see the equivalent
598"composite" command option name. </p>
599
600<table class="doc">
601 <tbody>
602 <tr valign="top">
603 <th align="left" style="width: 8%">Method</th>
604 <th align="left">Description</th>
605 </tr>
606
607 <tr valign="top">
608 <td valign="top">dissolve</td>
609 <td valign="top">Arguments:
610 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]611 <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]612 <br>Dissolve the 'source' image by the percentage given before overlaying
613 'over' the 'destination' image. If <em class="arg">src_percent</em> is
614 greater than 100, it starts dissolving the main image so it will
615 become transparent at a value of '<kbd class="arg">200</kbd>'. If
616 both percentages are given, each image are dissolved to the
617 percentages given.
618 </td>
619 </tr>
620
621 <tr valign="top">
622 <td valign="top">blend</td>
623 <td valign="top">Arguments:
624 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]625 <br>Equivalent to "<code>composite</code>" <a
626 href="../www/command-line-options.html#blend">-blend</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]627 <br>Average the images together ('plus') according to the percentages
628 given and each pixels transparency. If only a single percentage value
629 is given it sets the weight of the composite or 'source' image, while
630 the background image is weighted by the exact opposite amount. That is
631 a <kbd>-blend 30</kbd> merges 30% of the 'source' image with 70% of
632 the 'destination' image. Thus it is equivalent to <kbd>-blend
633 30x70</kbd>.
634 </td>
635 </tr>
636
637 <tr valign="top">
638 <td valign="top">mathematics</td>
639 <td valign="top">Arguments: <em class="arg">A, B, C, D</em>
640 <br>Not available in "<code>composite</code>" at this time.
641 <br>Merge the source and destination images according to the formula
642 <br>&nbsp; &nbsp; &nbsp;<code>A*Sc*Dc + B*Sc + C*Dc + D</code>
643 <br>Can be used to generate a custom composition method that would
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]644 otherwise need to be implemented using the slow <a
645 href="../www/command-line-options.html#fx">-fx</a> DIY image operator. Added
646 to ImageMagick version 6.5.4-3.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]647 <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]648 if the 'Sync' flag is removed from <a
649 href="../www/command-line-options.html#channel" >-channel</a>, just like all
650 the other mathematical compostion methods above.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]651 </td>
652 </tr>
653
654 <tr valign="top">
655 <td valign="top">modulate</td>
656 <td valign="top">Arguments:
657 <em class="arg">brightness</em>[x<em class="arg">saturation</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]658 <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]659 <br>Take a grayscale image (with alpha mask) and modify the destination
660 image's brightness according to watermark image's grayscale value and
661 the <em class="arg">brightness</em> percentage. The destinations
662 color saturation attribute is just direct modified by the <em
663 class="arg">saturation</em> percentage, which defaults to 100 percent
664 (no color change).
665
666 </td>
667 </tr>
668
669 <tr valign="top">
670 <td valign="top">displace</td>
671 <td valign="top">Arguments:
672 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em>][!][%]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]673 <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]674 <br>With this option, the 'overlay' image, and optionally the 'mask'
675 image, is used as a relative displacement map, which is used to
676 displace the lookup of what part of the destination image is seen at
677 each point of the overlaid area. Much like the displacement map is a
678 'lens' that distorts the original 'background' image behind it.
679 <br><br>
680 The X-scale is modilated by the 'red' channel of the overlay image
681 while the Y-scale is modulated by the green channel, (the mask image
682 if given is rolled into green channel of the overlay image. This
683 separation allows you to modulate the X and Y lookup displacement
684 separatally allowing you to di 2 dimentional displacements, rather
685 than 1 dimentional verctored displacements (using grayscale image).
686 <br><br>
687 If the overlay image contains transparency this is used as a mask
688 of the resulting image to remove 'invalid' pixels.
689 <br><br>
690 The '%' flag makes the displacement scale relative to the size of the
691 overlay image (100% = half width/height of image). Using '!' switches
692 percentage arguments to refer to the destination image size instead.
693 <br><br>
694 Special flags were added Added to ImageMagick version 6.5.3-5.
695 </td>
696 </tr>
697
698 <tr valign="top">
699 <td valign="top">distort</td>
700 <td valign="top">Arguments:
701 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em
702 >[+<em class="arg">X-center</em>+<em class="arg">Y-center</em>]][!][%]
703 <br>Not available in "<code>composite</code>" at this time.
704 <br>Exactly as per 'Displace' (above), but using absolute coordinates,
705 relative to the center of the overlay (or that given). Basically
706 allows you to generate absolute distortion maps where 'black' will
707 look up the left/top edge, and 'white' looks up the bottom/right
708 edge of the destination image, according to the scale given.
709 <br><br>
710 The '!' flag not only switches percentage scaling, to use the
711 destination image, but also the image the center offset of the lookup.
712 This means the overlay can lookup a completely different region of the
713 destination image.
714 <br><br>
715 Added to ImageMagick version 6.5.3-5.
716 </td>
717 </tr>
718
719 <tr valign="top">
720 <td valign="top">blur</td>
721 <td valign="top">Arguments:
722 <em class="arg">Width</em>[x<em class="arg">Height</em
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]723 >[+<em class="arg">Angle</em>][+<em class="arg">Angle2</em>]]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]724 <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]725 <br>A Variable Blur Mapping Composition method, where each pixel in the
726 overlaid region is replaced with an Elliptical Weighted Average (EWA),
727 with an ellipse (typically a circle) of the given sigma size, scaled
728 according to overlay (source image) grayscale mapping.
729 <br><br>
730 As per 'Displace' and 'Distort', the red channel will modulate the
731 width of the ellipse, while the green channel will modulate the height
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]732 of the ellipse. If a single Angle value is given in the arguments,
733 then the ellipse will then be rotated by the angle specifed.
734 <br><br>
735 Normally the blue channel of the mapping overlay image is ignored.
736 However if a second ellipse angle is given, then it is assumed that
737 the blue channel defines a variable angle for the ellipse ranging from
738 the first angle to the second angle given. This allows to generate
739 radial blurs, or a rough approximation for rotational blur. Or any mix
740 of the two.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]741 <br><br>
742 Added to ImageMagick version 6.5.4-0.
743 </td>
744 </tr>
745
746 </tbody>
747</table>
748
749<p>To print a complete list of all the available compose operators, use <a
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]750href="../www/command-line-options.html#list">-list compose</a>.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]751
752
753
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