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218
cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]219<h1>ImageMagick Image Composition</h1>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]220<p>This page descibed the Image composition methods that is used to define how
221two images should be merged together in various image operations. For the
222Command Line API it is typically set using the <A
223HREF="../www/command-line-options.html#compose" >-compose</A> setting option. </p>
224
225
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]226<p>The description of composition uses abstract terminology in order to allow
227the description to be more precise, while avoiding constant values which are
228specific to a particular build configuration. Each image pixel is represented
229by red, green, and blue levels (which are equal for a gray pixel). The
230build-dependent value <em class="QR">QuantumRange</em> is the maximum integral
231value which may be stored, per pixel, in the red, green, or blue channels of
232the image. Each image pixel may also optionally (if the image matte channel is
233enabled) have an associated level of opacity, ranging from <em>opaque</em> to
234<em>transparent</em>, which may be used to determine the influence of the pixel
235color when compositing the pixel with another image pixel. If the image matte
236channel is disabled, then all pixels in the image are treated as opaque. The
237color of an opaque pixel is fully visible while the color of a transparent
238pixel color is entirely absent (pixel color is ignored).</p>
239
240<p>By definition, raster images have a rectangular shape. All image rows are of
241equal length, as are all image columns. By treating the alpha channel as a
242visual "mask" the rectangular image may be given a "shape" by treating the
243alpha channel as a cookie-cutter for the image. This is done by setting the
244pixels within the shape to be opaque, with pixels outside the shape set as
245transparent. Pixels on the boundary of the shape may be between opaque and
246transparent in order to provide antialiasing (visually smooth edges). The
247description of the composition operators use this concept of image "shape" in
248order to make the description of the operators easier to understand. While it
249is convenient to describe the operators in terms of "shapes" they are by no
250means limited to mask-style operations since they are based on continuous
251floating-point mathematics rather than simple boolean operations.</p>
252
253<p>The following alpha blending (Duff-Porter) compose methods are available:</p>
254
255<table class="doc">
256 <tbody>
257 <tr valign="top">
258 <th align="left" style="width: 8%">Method</th>
259 <th align="left">Description</th>
260 </tr>
261
262 <tr valign="top">
263 <td valign="top">clear</td>
264 <td valign="top">Both the color and the alpha of the destination are
265 cleared. Neither the source nor the destination are used (except for
266 destinations size and other meta-data which is always preserved.</td>
267 </tr>
268
269 <tr valign="top">
270 <td valign="top">src</td>
271 <td valign="top">The source is copied to the destination. The destination
272 is not used as input, though it is cleared.</td>
273 </tr>
274
275 <tr valign="top">
276 <td valign="top">dst</td>
277 <td valign="top">The destination is left untouched. The source image is
278 completely ignored.</td>
279 </tr>
280
281 <tr valign="top">
282 <td valign="top">src-over</td>
283 <td valign="top">The source is composited over the destination. this is
284 the default alpha blending compose method, when neither the compose
285 setting is set, nor is set in the image meta-data.</td>
286 </tr>
287
288 <tr valign="top">
289 <td valign="top">dst-over</td>
290 <td valign="top">The destination is composited over the source and the
291 result replaces the destination.</td>
292 </tr>
293
294 <tr valign="top">
295 <td valign="top">src-in</td>
296 <td valign="top">The part of the source lying inside of the destination
297 replaces the destination.</td>
298 </tr>
299
300 <tr valign="top">
301 <td valign="top">dst-in</td>
302 <td valign="top">The part of the destination lying inside of the source
303 replaces the destination. Areas not overlaid are cleared.</td>
304 </tr>
305
306 <tr valign="top">
307 <td valign="top">src-out</td>
308 <td valign="top">The part of the source lying outside of the destination
309 replaces the destination.</td>
310 </tr>
311
312 <tr valign="top">
313 <td valign="top">dst-out</td>
314 <td valign="top">The part of the destination lying outside of the source
315 replaces the destination.</td>
316 </tr>
317
318 <tr valign="top">
319 <td valign="top">src-atop</td>
320 <td valign="top">The part of the source lying inside of the destination is
321 composited onto the destination.</td>
322 </tr>
323
324 <tr valign="top">
325 <td valign="top">dst-atop</td>
326 <td valign="top">The part of the destination lying inside of the source is
327 composited over the source and replaces the destination. Areas not
328 overlaid are cleared. </td>
329 </tr>
330
331 <tr valign="top">
332 <td valign="top">xor</td>
333 <td valign="top">The part of the source that lies outside of the
334 destination is combined with the part of the destination that lies
335 outside of the source. Source or Destination, but not both. </td>
336 </tr>
337
338 </tbody>
339</table>
340
341<p>Any of the 'Src-*' methods can also be specified without the 'Src-' part.
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]342For example the default compose method can be specified as just 'Over'.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]343
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]344<p>Many of these compose methods will clear the destination image which was
345not overlaid by the source image. This is to be expected as part of that
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]346specific composition methods defintion. You can disable this by setting the
347special <A HREF="../www/command-line-options.html#define"
348>-define</A> 'compose:outside-overlay' to a value of 'false' will turn off
349this behaviour. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]350
351<p>On top of the above 12 Duff-Porter Alpha Composition methods, one special
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]352related method '<kbd>Copy</kbd>' has been provided. This is equivalent to
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]353using the '<kbd>Src</kbd>' with the special <A HREF="../www/command-line-options.html#define"
354>-define</A> option '<kbd>compose:outside-overlay</kbd>' set to
355'<kbd>false</kbd>', so as to only modify the overlaid area, without clearing
356the rest of the image outside the overlaid area. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]357
358<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]359
360<p>The following mathemathical composition methods are also available. </p>
361
362<table class="doc">
363 <tbody>
364 <tr valign="top">
365 <th align="left" style="width: 8%">Method</th>
366 <th align="left">Description</th>
367 </tr>
368
369 <tr valign="top">
370 <td valign="top">multiply</td>
371 <td valign="top">The source is multiplied by the destination and replaces
372 the destination. The resultant color is always at least as dark as
373 either of the two constituent colors. Multiplying any color with black
374 produces black. Multiplying any color with white leaves the original
375 color unchanged.</td>
376 </tr>
377
378 <tr valign="top">
379 <td valign="top">screen</td>
380 <td valign="top">The source and destination are complemented and then
381 multiplied and then replace the destination. The resultant color is
382 always at least as light as either of the two constituent colors.
383 Screening any color with white produces white. Screening any color
384 with black leaves the original color unchanged.</td>
385 </tr>
386
387 <tr valign="top">
388 <td valign="top">plus</td>
389 <td valign="top">The source is added to the destination and replaces the
390 destination. This operator is useful for averaging or a controled
391 merger of two images, rather than a direct overlay.</td>
392 </tr>
393
394 <tr valign="top">
395 <td valign="top">add</td>
396 <td valign="top">As per 'plus' but transparency data is treated as matte
397 values. As such any transparent areas in either image remain
398 transparent. </td>
399 </tr>
400
401 <tr valign="top">
402 <td valign="top">minus</td>
403 <td valign="top">Subtract the colors in the source image from the
404 destination image. When transparency is involved, opaque areas is
405 subtracted from any destination opaque areas. </td>
406 </tr>
407
408 <tr valign="top">
409 <td valign="top">subtract</td>
410 <td valign="top">Subtract the colors in the source image from the
411 destination image. When transparency is involved transparent areas are
412 subtracted, so only the opaque areas in the source remain opaque in
413 the destination image. </td>
414 </tr>
415
416 <tr valign="top">
417 <td valign="top">difference</td>
418 <td valign="top">Subtracts the darker of the two constituent colors from
419 the lighter. Painting with white inverts the destination color.
420 Painting with black produces no change.</td>
421 </tr>
422
423 <tr valign="top">
424 <td valign="top">exclusion</td>
425 <td valign="top">Produces an effect similar to that of 'difference', but
426 appears as lower contrast. Painting with white inverts the
427 destination color. Painting with black produces no change.</td>
428 </tr>
429
430 <tr valign="top">
431 <td valign="top">darken</td>
432 <td valign="top">Selects the darker of the destination and source colors.
433 The destination is replaced with the source when the source is darker,
434 otherwise it is left unchanged.</td>
435 </tr>
436
437 <tr valign="top">
438 <td valign="top">lighten</td>
439 <td valign="top">Selects the lighter of the destination and source colors.
440 The destination is replaced with the source when the source is
441 lighter, otherwise it is left unchanged. </td>
442 </tr>
443
444 </tbody>
445</table>
446
447<p>Typically these use the default 'Over' alpha blending when transparencies
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]448are also involved, except for 'Plus' which uses a 'plus' alpha blending. This
449means the alpha channel of both images will only be used to ensure that any
450visible input remains visible even in parts not overlaid. It also means that
451any values are weighted by the alpha channel of the input and output images.
452This 'Over' alpha blending is also applied to the lighting composition methods
453below. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]454
455<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]456(enabled by default) with the <a href="../www/command-line-options.html#channel"
457>-channel</a> setting, then the above mathematical compositions will nolonger
cristy2dcd6822011-06-13 16:21:20 +0000[diff] [blame]458synchronise its actions with the alpha channel. Instead the math composition
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]459will be applied on an individual channel basis as defined by the <a
460href="../www/command-line-options.html#channel"
461>-channel</a>. This includes the alpha channel. This special usage
462allows you to perform true mathematics of the image channels, without alpha
463compostion effects, becomming involved. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]464
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]465<p>This special flag is not applied to the lighting composition methods (see
466below) even though they are closely related to mathematical composition
467methods.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]468
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]469<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]470
471<p>The following lighting composition methods are also available. </p>
472
473<table class="doc">
474 <tbody>
475 <tr valign="top">
476 <th align="left" style="width: 8%">Method</th>
477 <th align="left">Description</th>
478 </tr>
479
480 <tr valign="top">
481 <td valign="top">linear-dodge</td>
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]482 <td valign="top">This is equivalent to 'Plus' in that the color channels
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]483 are simply added, however it does not 'Plus' the alpha channel, but
484 uses the normal 'Over' alpha blending, which transparencies are
485 involved. Produces a sort of additive multiply-like result. Added
486 ImageMagick version 6.5.4-3. </td>
487 </tr>
488
489 <tr valign="top">
490 <td valign="top">linear-burn</td>
491 <td valign="top">As 'Linear-Dodge', but also subtract one from the result.
492 Sort of a additive 'Screen' of the images. Added ImageMagick version
493 6.5.4-3. </td>
494 </tr>
495
496 <tr valign="top">
497 <td valign="top">color-dodge</td>
498 <td valign="top">Brightens the destination color to reflect the source
499 color. Painting with black produces no change.</td>
500 </tr>
501
502 <tr valign="top">
503 <td valign="top">color-burn</td>
504 <td valign="top">Darkens the destination color to reflect the source
505 color. Painting with white produces no change. Fixed in ImageMagick
506 version 6.5.4-3. </td>
507 </tr>
508
509 <tr valign="top">
510 <td valign="top">overlay</td>
511 <td valign="top">Multiplies or screens the colors, dependent on the
512 destination color. Source colors overlay the destination whilst
513 preserving its highlights and shadows. The destination color is not
514 replaced, but is mixed with the source color to reflect the lightness
515 or darkness of the destination.</td>
516 </tr>
517
518 <tr valign="top">
519 <td valign="top">hard-light</td>
520 <td valign="top">Multiplies or screens the colors, dependent on the source
521 color value. If the source color is lighter than 0.5, the destination
522 is lightened as if it were screened. If the source color is darker
523 than 0.5, the destination is darkened, as if it were multiplied. The
524 degree of lightening or darkening is proportional to the difference
525 between the source color and 0.5. If it is equal to 0.5 the
526 destination is unchanged. Painting with pure black or white produces
527 black or white.</td>
528 </tr>
529
530
531 <tr valign="top">
532 <td valign="top">linear-light</td>
533 <td valign="top">Like 'Hard-Light' but using linear-dodge and linear-burn
534 instead. Increases contrast slightly with an impact on the
535 foreground's tonal values.</td>
536 </tr>
537
538 <tr valign="top">
539 <td valign="top">soft-light</td>
540 <td valign="top">Darkens or lightens the colors, dependent on the source
541 color value. If the source color is lighter than 0.5, the destination
542 is lightened. If the source color is darker than 0.5, the destination
543 is darkened, as if it were burned in. The degree of darkening or
544 lightening is proportional to the difference between the source color
545 and 0.5. If it is equal to 0.5, the destination is unchanged. Painting
546 with pure black or white produces a distinctly darker or lighter area,
547 but does not result in pure black or white. Fixed in ImageMagick
548 version 6.5.4-3. </td>
549 </tr>
550
551 <tr valign="top">
552 <td valign="top">pegtop-light</td>
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]553 <td valign="top">Almost equivalent to 'Soft-Light', but using a
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]554 continuious mathematical formula rather than two conditionally
555 selected formulae. Added ImageMagick version 6.5.4-3. </td>
556 </tr>
557
558 <tr valign="top">
559 <td valign="top">vivid-light</td>
560 <td valign="top">A modified 'Linear-Light' designed to preserve very stong
561 primary and secondary colors in the image. Added ImageMagick version
562 6.5.4-3. </td>
563 </tr>
564
565 <tr valign="top">
566 <td valign="top">pin-light</td>
567 <td valign="top">Similar to 'Hard-Light', but using sharp linear shadings,
568 to similate the effects of a strong 'pinhole' light source. Added
569 ImageMagick version 6.5.4-3. </td>
570 </tr>
571
572 </tbody>
573</table>
574
575
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]576<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]577
578<p>Also included are these special purpose compose methods:</p>
579
580<table class="doc">
581 <tbody>
582 <tr valign="top">
583 <th align="left" style="width: 8%">Method</th>
584 <th align="left">Description</th>
585 </tr>
586
587 <tr valign="top">
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]588 <td valign="top">copy</td>
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]589 <td valign="top">This is equivalent to the Duff-Porter composition method
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]590 '<kbd>Src,</kbd>' but without clearing the parts of the destination
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]591 image that is not overlaid. </td>
592 </tr>
593
594 <tr valign="top">
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]595 <td valign="top">copy-*</td>
596 <td valign="top">Copy the specified channel (Red, Green, Blue, Cyan,
597 Magenta, Yellow, Black, or Opacity) in the source image to the
598 same channel in the destination image. If the channel specified
599 does not exist in the source image, (which can only happen for methods,
600 '<kbd>copy-opacity</kbd>' or '<kbd>copy-black</kbd>') then it is
601 assumed that the source image is a special grayscale channel image
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]602 of the values that is to be copied. </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]603 </tr>
604
605 <tr valign="top">
606 <td valign="top">change-mask</td>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]607 <td valign="top">Replace any destination pixel that is the similar to the
608 source images pixel (as defined by the current <a
609 href="../www/command-line-options.html#fuzz">-fuzz</a> factor), with transparency.
610 </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]611 </tr>
612 </tbody>
613</table>
614
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]615<br><br>
616
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]617<p>On top of these composed methods are a few special ones that not only require
618the two images that are being merged or overlaid, but have some extra numerical
619arguments, which are tabled below. </p>
620
621<p>In the "<code>composite</code>" command these composition methods are
622selected using special options with the arguments needed. They are usually,
623but not always, the same name as the composte 'method' they use, and replaces
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]624the normal use of the <a href="../www/command-line-options.html#compose" >-compose</a>
625setting in the "<code>composite</code>" command. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]626
627<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>composite ... -blend 50x50 ...</span></p>
628<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]629these extra arguments to its <a href="../www/command-line-options.html#composite"
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]630>-composite</a> operator, using the special <a href="../www/command-line-options.html#define">-define</a>
631attribute of '<kbd class="arg">compose:args</kbd>'. This means you can now
632make use of these special argumented <a href="../www/command-line-options.html#compose"
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]633>-compose</a> methods, those the argument and the method both need to be set
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]634separately. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]635
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]636<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]637<p>The following is a table of these special 'argumented' compose methods,
638with a brief summary of what they do. For more details see the equivalent
639"composite" command option name. </p>
640
641<table class="doc">
642 <tbody>
643 <tr valign="top">
644 <th align="left" style="width: 8%">Method</th>
645 <th align="left">Description</th>
646 </tr>
647
648 <tr valign="top">
649 <td valign="top">dissolve</td>
650 <td valign="top">Arguments:
651 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]652 <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]653 <br>Dissolve the 'source' image by the percentage given before overlaying
654 'over' the 'destination' image. If <em class="arg">src_percent</em> is
655 greater than 100, it starts dissolving the main image so it will
656 become transparent at a value of '<kbd class="arg">200</kbd>'. If
657 both percentages are given, each image are dissolved to the
658 percentages given.
659 </td>
660 </tr>
661
662 <tr valign="top">
663 <td valign="top">blend</td>
664 <td valign="top">Arguments:
665 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]666 <br>Equivalent to "<code>composite</code>" <a
667 href="../www/command-line-options.html#blend">-blend</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]668 <br>Average the images together ('plus') according to the percentages
669 given and each pixels transparency. If only a single percentage value
670 is given it sets the weight of the composite or 'source' image, while
671 the background image is weighted by the exact opposite amount. That is
672 a <kbd>-blend 30</kbd> merges 30% of the 'source' image with 70% of
673 the 'destination' image. Thus it is equivalent to <kbd>-blend
674 30x70</kbd>.
675 </td>
676 </tr>
677
678 <tr valign="top">
679 <td valign="top">mathematics</td>
680 <td valign="top">Arguments: <em class="arg">A, B, C, D</em>
681 <br>Not available in "<code>composite</code>" at this time.
682 <br>Merge the source and destination images according to the formula
683 <br>&nbsp; &nbsp; &nbsp;<code>A*Sc*Dc + B*Sc + C*Dc + D</code>
684 <br>Can be used to generate a custom composition method that would
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]685 otherwise need to be implemented using the slow <a
686 href="../www/command-line-options.html#fx">-fx</a> DIY image operator. Added
687 to ImageMagick version 6.5.4-3.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]688 <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]689 if the 'Sync' flag is removed from <a
690 href="../www/command-line-options.html#channel" >-channel</a>, just like all
691 the other mathematical compostion methods above.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]692 </td>
693 </tr>
694
695 <tr valign="top">
696 <td valign="top">modulate</td>
697 <td valign="top">Arguments:
698 <em class="arg">brightness</em>[x<em class="arg">saturation</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]699 <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]700 <br>Take a grayscale image (with alpha mask) and modify the destination
701 image's brightness according to watermark image's grayscale value and
702 the <em class="arg">brightness</em> percentage. The destinations
703 color saturation attribute is just direct modified by the <em
704 class="arg">saturation</em> percentage, which defaults to 100 percent
705 (no color change).
706
707 </td>
708 </tr>
709
710 <tr valign="top">
711 <td valign="top">displace</td>
712 <td valign="top">Arguments:
713 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em>][!][%]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]714 <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]715 <br>With this option, the 'overlay' image, and optionally the 'mask'
716 image, is used as a relative displacement map, which is used to
717 displace the lookup of what part of the destination image is seen at
718 each point of the overlaid area. Much like the displacement map is a
719 'lens' that distorts the original 'background' image behind it.
720 <br><br>
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]721 The X-scale is modulated by the 'red' channel of the overlay image
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]722 while the Y-scale is modulated by the green channel, (the mask image
723 if given is rolled into green channel of the overlay image. This
724 separation allows you to modulate the X and Y lookup displacement
cristy29c5c992011-06-25 13:58:49 +0000[diff] [blame]725 separately allowing you to do 2-dimensional displacements, rather
726 than 1-dimensional verctored displacements (using grayscale image).
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]727 <br><br>
728 If the overlay image contains transparency this is used as a mask
729 of the resulting image to remove 'invalid' pixels.
730 <br><br>
731 The '%' flag makes the displacement scale relative to the size of the
732 overlay image (100% = half width/height of image). Using '!' switches
733 percentage arguments to refer to the destination image size instead.
734 <br><br>
735 Special flags were added Added to ImageMagick version 6.5.3-5.
736 </td>
737 </tr>
738
739 <tr valign="top">
740 <td valign="top">distort</td>
741 <td valign="top">Arguments:
742 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em
743 >[+<em class="arg">X-center</em>+<em class="arg">Y-center</em>]][!][%]
744 <br>Not available in "<code>composite</code>" at this time.
745 <br>Exactly as per 'Displace' (above), but using absolute coordinates,
746 relative to the center of the overlay (or that given). Basically
747 allows you to generate absolute distortion maps where 'black' will
748 look up the left/top edge, and 'white' looks up the bottom/right
749 edge of the destination image, according to the scale given.
750 <br><br>
751 The '!' flag not only switches percentage scaling, to use the
752 destination image, but also the image the center offset of the lookup.
753 This means the overlay can lookup a completely different region of the
754 destination image.
755 <br><br>
756 Added to ImageMagick version 6.5.3-5.
757 </td>
758 </tr>
759
760 <tr valign="top">
761 <td valign="top">blur</td>
762 <td valign="top">Arguments:
763 <em class="arg">Width</em>[x<em class="arg">Height</em
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]764 >[+<em class="arg">Angle</em>][+<em class="arg">Angle2</em>]]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]765 <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]766 <br>A Variable Blur Mapping Composition method, where each pixel in the
767 overlaid region is replaced with an Elliptical Weighted Average (EWA),
768 with an ellipse (typically a circle) of the given sigma size, scaled
769 according to overlay (source image) grayscale mapping.
770 <br><br>
771 As per 'Displace' and 'Distort', the red channel will modulate the
772 width of the ellipse, while the green channel will modulate the height
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]773 of the ellipse. If a single Angle value is given in the arguments,
774 then the ellipse will then be rotated by the angle specifed.
775 <br><br>
776 Normally the blue channel of the mapping overlay image is ignored.
777 However if a second ellipse angle is given, then it is assumed that
778 the blue channel defines a variable angle for the ellipse ranging from
779 the first angle to the second angle given. This allows to generate
780 radial blurs, or a rough approximation for rotational blur. Or any mix
781 of the two.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]782 <br><br>
783 Added to ImageMagick version 6.5.4-0.
784 </td>
785 </tr>
786
787 </tbody>
788</table>
789
790<p>To print a complete list of all the available compose operators, use <a
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]791href="../www/command-line-options.html#list">-list compose</a>.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]792
793
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