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cristydcca3fa2010-12-29 21:50:07 +0000[diff] [blame]200<h1>ImageMagick Image Composition</h1>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]201<p>This page descibed the Image composition methods that is used to define how
202two images should be merged together in various image operations. For the
203Command Line API it is typically set using the <A
204HREF="../www/command-line-options.html#compose" >-compose</A> setting option. </p>
205
206
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]207<p>The description of composition uses abstract terminology in order to allow
208the description to be more precise, while avoiding constant values which are
209specific to a particular build configuration. Each image pixel is represented
210by red, green, and blue levels (which are equal for a gray pixel). The
211build-dependent value <em class="QR">QuantumRange</em> is the maximum integral
212value which may be stored, per pixel, in the red, green, or blue channels of
213the image. Each image pixel may also optionally (if the image matte channel is
214enabled) have an associated level of opacity, ranging from <em>opaque</em> to
215<em>transparent</em>, which may be used to determine the influence of the pixel
216color when compositing the pixel with another image pixel. If the image matte
217channel is disabled, then all pixels in the image are treated as opaque. The
218color of an opaque pixel is fully visible while the color of a transparent
219pixel color is entirely absent (pixel color is ignored).</p>
220
221<p>By definition, raster images have a rectangular shape. All image rows are of
222equal length, as are all image columns. By treating the alpha channel as a
223visual "mask" the rectangular image may be given a "shape" by treating the
224alpha channel as a cookie-cutter for the image. This is done by setting the
225pixels within the shape to be opaque, with pixels outside the shape set as
226transparent. Pixels on the boundary of the shape may be between opaque and
227transparent in order to provide antialiasing (visually smooth edges). The
228description of the composition operators use this concept of image "shape" in
229order to make the description of the operators easier to understand. While it
230is convenient to describe the operators in terms of "shapes" they are by no
231means limited to mask-style operations since they are based on continuous
232floating-point mathematics rather than simple boolean operations.</p>
233
234<p>The following alpha blending (Duff-Porter) compose methods are available:</p>
235
236<table class="doc">
237 <tbody>
238 <tr valign="top">
239 <th align="left" style="width: 8%">Method</th>
240 <th align="left">Description</th>
241 </tr>
242
243 <tr valign="top">
244 <td valign="top">clear</td>
245 <td valign="top">Both the color and the alpha of the destination are
246 cleared. Neither the source nor the destination are used (except for
247 destinations size and other meta-data which is always preserved.</td>
248 </tr>
249
250 <tr valign="top">
251 <td valign="top">src</td>
252 <td valign="top">The source is copied to the destination. The destination
253 is not used as input, though it is cleared.</td>
254 </tr>
255
256 <tr valign="top">
257 <td valign="top">dst</td>
258 <td valign="top">The destination is left untouched. The source image is
259 completely ignored.</td>
260 </tr>
261
262 <tr valign="top">
263 <td valign="top">src-over</td>
264 <td valign="top">The source is composited over the destination. this is
265 the default alpha blending compose method, when neither the compose
266 setting is set, nor is set in the image meta-data.</td>
267 </tr>
268
269 <tr valign="top">
270 <td valign="top">dst-over</td>
271 <td valign="top">The destination is composited over the source and the
272 result replaces the destination.</td>
273 </tr>
274
275 <tr valign="top">
276 <td valign="top">src-in</td>
277 <td valign="top">The part of the source lying inside of the destination
278 replaces the destination.</td>
279 </tr>
280
281 <tr valign="top">
282 <td valign="top">dst-in</td>
283 <td valign="top">The part of the destination lying inside of the source
284 replaces the destination. Areas not overlaid are cleared.</td>
285 </tr>
286
287 <tr valign="top">
288 <td valign="top">src-out</td>
289 <td valign="top">The part of the source lying outside of the destination
290 replaces the destination.</td>
291 </tr>
292
293 <tr valign="top">
294 <td valign="top">dst-out</td>
295 <td valign="top">The part of the destination lying outside of the source
296 replaces the destination.</td>
297 </tr>
298
299 <tr valign="top">
300 <td valign="top">src-atop</td>
301 <td valign="top">The part of the source lying inside of the destination is
302 composited onto the destination.</td>
303 </tr>
304
305 <tr valign="top">
306 <td valign="top">dst-atop</td>
307 <td valign="top">The part of the destination lying inside of the source is
308 composited over the source and replaces the destination. Areas not
309 overlaid are cleared. </td>
310 </tr>
311
312 <tr valign="top">
313 <td valign="top">xor</td>
314 <td valign="top">The part of the source that lies outside of the
315 destination is combined with the part of the destination that lies
316 outside of the source. Source or Destination, but not both. </td>
317 </tr>
318
319 </tbody>
320</table>
321
322<p>Any of the 'Src-*' methods can also be specified without the 'Src-' part.
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]323For example the default compose method can be specified as just 'Over'.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]324
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]325<p>Many of these compose methods will clear the destination image which was
326not overlaid by the source image. This is to be expected as part of that
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]327specific composition methods defintion. You can disable this by setting the
328special <A HREF="../www/command-line-options.html#define"
329>-define</A> 'compose:outside-overlay' to a value of 'false' will turn off
330this behaviour. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]331
332<p>On top of the above 12 Duff-Porter Alpha Composition methods, one special
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]333related method '<kbd>Copy</kbd>' has been provided. This is equivalent to
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]334using the '<kbd>Src</kbd>' with the special <A HREF="../www/command-line-options.html#define"
335>-define</A> option '<kbd>compose:outside-overlay</kbd>' set to
336'<kbd>false</kbd>', so as to only modify the overlaid area, without clearing
337the rest of the image outside the overlaid area. </p>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]338
339<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]340
341<p>The following mathemathical composition methods are also available. </p>
342
343<table class="doc">
344 <tbody>
345 <tr valign="top">
346 <th align="left" style="width: 8%">Method</th>
347 <th align="left">Description</th>
348 </tr>
349
350 <tr valign="top">
351 <td valign="top">multiply</td>
352 <td valign="top">The source is multiplied by the destination and replaces
353 the destination. The resultant color is always at least as dark as
354 either of the two constituent colors. Multiplying any color with black
355 produces black. Multiplying any color with white leaves the original
356 color unchanged.</td>
357 </tr>
358
359 <tr valign="top">
360 <td valign="top">screen</td>
361 <td valign="top">The source and destination are complemented and then
362 multiplied and then replace the destination. The resultant color is
363 always at least as light as either of the two constituent colors.
364 Screening any color with white produces white. Screening any color
365 with black leaves the original color unchanged.</td>
366 </tr>
367
368 <tr valign="top">
369 <td valign="top">plus</td>
370 <td valign="top">The source is added to the destination and replaces the
371 destination. This operator is useful for averaging or a controled
372 merger of two images, rather than a direct overlay.</td>
373 </tr>
374
375 <tr valign="top">
376 <td valign="top">add</td>
377 <td valign="top">As per 'plus' but transparency data is treated as matte
378 values. As such any transparent areas in either image remain
379 transparent. </td>
380 </tr>
381
382 <tr valign="top">
383 <td valign="top">minus</td>
384 <td valign="top">Subtract the colors in the source image from the
385 destination image. When transparency is involved, opaque areas is
386 subtracted from any destination opaque areas. </td>
387 </tr>
388
389 <tr valign="top">
390 <td valign="top">subtract</td>
391 <td valign="top">Subtract the colors in the source image from the
392 destination image. When transparency is involved transparent areas are
393 subtracted, so only the opaque areas in the source remain opaque in
394 the destination image. </td>
395 </tr>
396
397 <tr valign="top">
398 <td valign="top">difference</td>
399 <td valign="top">Subtracts the darker of the two constituent colors from
400 the lighter. Painting with white inverts the destination color.
401 Painting with black produces no change.</td>
402 </tr>
403
404 <tr valign="top">
405 <td valign="top">exclusion</td>
406 <td valign="top">Produces an effect similar to that of 'difference', but
407 appears as lower contrast. Painting with white inverts the
408 destination color. Painting with black produces no change.</td>
409 </tr>
410
411 <tr valign="top">
412 <td valign="top">darken</td>
413 <td valign="top">Selects the darker of the destination and source colors.
414 The destination is replaced with the source when the source is darker,
415 otherwise it is left unchanged.</td>
416 </tr>
417
418 <tr valign="top">
419 <td valign="top">lighten</td>
420 <td valign="top">Selects the lighter of the destination and source colors.
421 The destination is replaced with the source when the source is
422 lighter, otherwise it is left unchanged. </td>
423 </tr>
424
425 </tbody>
426</table>
427
428<p>Typically these use the default 'Over' alpha blending when transparencies
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]429are also involved, except for 'Plus' which uses a 'plus' alpha blending. This
430means the alpha channel of both images will only be used to ensure that any
431visible input remains visible even in parts not overlaid. It also means that
432any values are weighted by the alpha channel of the input and output images.
433This 'Over' alpha blending is also applied to the lighting composition methods
434below. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]435
436<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]437(enabled by default) with the <a href="../www/command-line-options.html#channel"
438>-channel</a> setting, then the above mathematical compositions will nolonger
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]439syncronise its actions with the alpha channel. Instead the math composition
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]440will be applied on an individual channel basis as defined by the <a
441href="../www/command-line-options.html#channel"
442>-channel</a>. This includes the alpha channel. This special usage
443allows you to perform true mathematics of the image channels, without alpha
444compostion effects, becomming involved. </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]445
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]446<p>This special flag is not applied to the lighting composition methods (see
447below) even though they are closely related to mathematical composition
448methods.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]449
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]450<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]451
452<p>The following lighting composition methods are also available. </p>
453
454<table class="doc">
455 <tbody>
456 <tr valign="top">
457 <th align="left" style="width: 8%">Method</th>
458 <th align="left">Description</th>
459 </tr>
460
461 <tr valign="top">
462 <td valign="top">linear-dodge</td>
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]463 <td valign="top">This is equivalent to 'Plus' in that the color channels
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]464 are simply added, however it does not 'Plus' the alpha channel, but
465 uses the normal 'Over' alpha blending, which transparencies are
466 involved. Produces a sort of additive multiply-like result. Added
467 ImageMagick version 6.5.4-3. </td>
468 </tr>
469
470 <tr valign="top">
471 <td valign="top">linear-burn</td>
472 <td valign="top">As 'Linear-Dodge', but also subtract one from the result.
473 Sort of a additive 'Screen' of the images. Added ImageMagick version
474 6.5.4-3. </td>
475 </tr>
476
477 <tr valign="top">
478 <td valign="top">color-dodge</td>
479 <td valign="top">Brightens the destination color to reflect the source
480 color. Painting with black produces no change.</td>
481 </tr>
482
483 <tr valign="top">
484 <td valign="top">color-burn</td>
485 <td valign="top">Darkens the destination color to reflect the source
486 color. Painting with white produces no change. Fixed in ImageMagick
487 version 6.5.4-3. </td>
488 </tr>
489
490 <tr valign="top">
491 <td valign="top">overlay</td>
492 <td valign="top">Multiplies or screens the colors, dependent on the
493 destination color. Source colors overlay the destination whilst
494 preserving its highlights and shadows. The destination color is not
495 replaced, but is mixed with the source color to reflect the lightness
496 or darkness of the destination.</td>
497 </tr>
498
499 <tr valign="top">
500 <td valign="top">hard-light</td>
501 <td valign="top">Multiplies or screens the colors, dependent on the source
502 color value. If the source color is lighter than 0.5, the destination
503 is lightened as if it were screened. If the source color is darker
504 than 0.5, the destination is darkened, as if it were multiplied. The
505 degree of lightening or darkening is proportional to the difference
506 between the source color and 0.5. If it is equal to 0.5 the
507 destination is unchanged. Painting with pure black or white produces
508 black or white.</td>
509 </tr>
510
511
512 <tr valign="top">
513 <td valign="top">linear-light</td>
514 <td valign="top">Like 'Hard-Light' but using linear-dodge and linear-burn
515 instead. Increases contrast slightly with an impact on the
516 foreground's tonal values.</td>
517 </tr>
518
519 <tr valign="top">
520 <td valign="top">soft-light</td>
521 <td valign="top">Darkens or lightens the colors, dependent on the source
522 color value. If the source color is lighter than 0.5, the destination
523 is lightened. If the source color is darker than 0.5, the destination
524 is darkened, as if it were burned in. The degree of darkening or
525 lightening is proportional to the difference between the source color
526 and 0.5. If it is equal to 0.5, the destination is unchanged. Painting
527 with pure black or white produces a distinctly darker or lighter area,
528 but does not result in pure black or white. Fixed in ImageMagick
529 version 6.5.4-3. </td>
530 </tr>
531
532 <tr valign="top">
533 <td valign="top">pegtop-light</td>
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]534 <td valign="top">Almost equivalent to 'Soft-Light', but using a
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]535 continuious mathematical formula rather than two conditionally
536 selected formulae. Added ImageMagick version 6.5.4-3. </td>
537 </tr>
538
539 <tr valign="top">
540 <td valign="top">vivid-light</td>
541 <td valign="top">A modified 'Linear-Light' designed to preserve very stong
542 primary and secondary colors in the image. Added ImageMagick version
543 6.5.4-3. </td>
544 </tr>
545
546 <tr valign="top">
547 <td valign="top">pin-light</td>
548 <td valign="top">Similar to 'Hard-Light', but using sharp linear shadings,
549 to similate the effects of a strong 'pinhole' light source. Added
550 ImageMagick version 6.5.4-3. </td>
551 </tr>
552
553 </tbody>
554</table>
555
556
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]557<br><br>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]558
559<p>Also included are these special purpose compose methods:</p>
560
561<table class="doc">
562 <tbody>
563 <tr valign="top">
564 <th align="left" style="width: 8%">Method</th>
565 <th align="left">Description</th>
566 </tr>
567
568 <tr valign="top">
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]569 <td valign="top">copy</td>
cristybaacd172011-04-30 23:11:03 +0000[diff] [blame]570 <td valign="top">This is equivalent to the Duff-Porter composition method
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]571 '<kbd>Src,</kbd>' but without clearing the parts of the destination
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]572 image that is not overlaid. </td>
573 </tr>
574
575 <tr valign="top">
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]576 <td valign="top">copy-*</td>
577 <td valign="top">Copy the specified channel (Red, Green, Blue, Cyan,
578 Magenta, Yellow, Black, or Opacity) in the source image to the
579 same channel in the destination image. If the channel specified
580 does not exist in the source image, (which can only happen for methods,
581 '<kbd>copy-opacity</kbd>' or '<kbd>copy-black</kbd>') then it is
582 assumed that the source image is a special grayscale channel image
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]583 of the values that is to be copied. </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]584 </tr>
585
586 <tr valign="top">
587 <td valign="top">change-mask</td>
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]588 <td valign="top">Replace any destination pixel that is the similar to the
589 source images pixel (as defined by the current <a
590 href="../www/command-line-options.html#fuzz">-fuzz</a> factor), with transparency.
591 </td>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]592 </tr>
593 </tbody>
594</table>
595
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]596<br><br>
597
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]598<p>On top of these composed methods are a few special ones that not only require
599the two images that are being merged or overlaid, but have some extra numerical
600arguments, which are tabled below. </p>
601
602<p>In the "<code>composite</code>" command these composition methods are
603selected using special options with the arguments needed. They are usually,
604but not always, the same name as the composte 'method' they use, and replaces
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]605the normal use of the <a href="../www/command-line-options.html#compose" >-compose</a>
606setting in the "<code>composite</code>" command. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]607
608<p class='crt'><span class="crtprompt"> $magick&gt; </span><span class='crtin'>composite ... -blend 50x50 ...</span></p>
609<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]610these extra arguments to its <a href="../www/command-line-options.html#composite"
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]611>-composite</a> operator, using the special <a href="../www/command-line-options.html#define">-define</a>
612attribute of '<kbd class="arg">compose:args</kbd>'. This means you can now
613make use of these special argumented <a href="../www/command-line-options.html#compose"
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]614>-compose</a> methods, those the argument and the method both need to be set
615separatally. For example... </p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]616
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]617<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]618<p>The following is a table of these special 'argumented' compose methods,
619with a brief summary of what they do. For more details see the equivalent
620"composite" command option name. </p>
621
622<table class="doc">
623 <tbody>
624 <tr valign="top">
625 <th align="left" style="width: 8%">Method</th>
626 <th align="left">Description</th>
627 </tr>
628
629 <tr valign="top">
630 <td valign="top">dissolve</td>
631 <td valign="top">Arguments:
632 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]633 <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]634 <br>Dissolve the 'source' image by the percentage given before overlaying
635 'over' the 'destination' image. If <em class="arg">src_percent</em> is
636 greater than 100, it starts dissolving the main image so it will
637 become transparent at a value of '<kbd class="arg">200</kbd>'. If
638 both percentages are given, each image are dissolved to the
639 percentages given.
640 </td>
641 </tr>
642
643 <tr valign="top">
644 <td valign="top">blend</td>
645 <td valign="top">Arguments:
646 <em class="arg">src_percent</em>[x<em class="arg">dst_percent</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]647 <br>Equivalent to "<code>composite</code>" <a
648 href="../www/command-line-options.html#blend">-blend</a>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]649 <br>Average the images together ('plus') according to the percentages
650 given and each pixels transparency. If only a single percentage value
651 is given it sets the weight of the composite or 'source' image, while
652 the background image is weighted by the exact opposite amount. That is
653 a <kbd>-blend 30</kbd> merges 30% of the 'source' image with 70% of
654 the 'destination' image. Thus it is equivalent to <kbd>-blend
655 30x70</kbd>.
656 </td>
657 </tr>
658
659 <tr valign="top">
660 <td valign="top">mathematics</td>
661 <td valign="top">Arguments: <em class="arg">A, B, C, D</em>
662 <br>Not available in "<code>composite</code>" at this time.
663 <br>Merge the source and destination images according to the formula
664 <br>&nbsp; &nbsp; &nbsp;<code>A*Sc*Dc + B*Sc + C*Dc + D</code>
665 <br>Can be used to generate a custom composition method that would
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]666 otherwise need to be implemented using the slow <a
667 href="../www/command-line-options.html#fx">-fx</a> DIY image operator. Added
668 to ImageMagick version 6.5.4-3.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]669 <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]670 if the 'Sync' flag is removed from <a
671 href="../www/command-line-options.html#channel" >-channel</a>, just like all
672 the other mathematical compostion methods above.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]673 </td>
674 </tr>
675
676 <tr valign="top">
677 <td valign="top">modulate</td>
678 <td valign="top">Arguments:
679 <em class="arg">brightness</em>[x<em class="arg">saturation</em>]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]680 <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]681 <br>Take a grayscale image (with alpha mask) and modify the destination
682 image's brightness according to watermark image's grayscale value and
683 the <em class="arg">brightness</em> percentage. The destinations
684 color saturation attribute is just direct modified by the <em
685 class="arg">saturation</em> percentage, which defaults to 100 percent
686 (no color change).
687
688 </td>
689 </tr>
690
691 <tr valign="top">
692 <td valign="top">displace</td>
693 <td valign="top">Arguments:
694 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em>][!][%]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]695 <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]696 <br>With this option, the 'overlay' image, and optionally the 'mask'
697 image, is used as a relative displacement map, which is used to
698 displace the lookup of what part of the destination image is seen at
699 each point of the overlaid area. Much like the displacement map is a
700 'lens' that distorts the original 'background' image behind it.
701 <br><br>
702 The X-scale is modilated by the 'red' channel of the overlay image
703 while the Y-scale is modulated by the green channel, (the mask image
704 if given is rolled into green channel of the overlay image. This
705 separation allows you to modulate the X and Y lookup displacement
706 separatally allowing you to di 2 dimentional displacements, rather
707 than 1 dimentional verctored displacements (using grayscale image).
708 <br><br>
709 If the overlay image contains transparency this is used as a mask
710 of the resulting image to remove 'invalid' pixels.
711 <br><br>
712 The '%' flag makes the displacement scale relative to the size of the
713 overlay image (100% = half width/height of image). Using '!' switches
714 percentage arguments to refer to the destination image size instead.
715 <br><br>
716 Special flags were added Added to ImageMagick version 6.5.3-5.
717 </td>
718 </tr>
719
720 <tr valign="top">
721 <td valign="top">distort</td>
722 <td valign="top">Arguments:
723 <em class="arg">X-scale</em>[x<em class="arg">Y-scale</em
724 >[+<em class="arg">X-center</em>+<em class="arg">Y-center</em>]][!][%]
725 <br>Not available in "<code>composite</code>" at this time.
726 <br>Exactly as per 'Displace' (above), but using absolute coordinates,
727 relative to the center of the overlay (or that given). Basically
728 allows you to generate absolute distortion maps where 'black' will
729 look up the left/top edge, and 'white' looks up the bottom/right
730 edge of the destination image, according to the scale given.
731 <br><br>
732 The '!' flag not only switches percentage scaling, to use the
733 destination image, but also the image the center offset of the lookup.
734 This means the overlay can lookup a completely different region of the
735 destination image.
736 <br><br>
737 Added to ImageMagick version 6.5.3-5.
738 </td>
739 </tr>
740
741 <tr valign="top">
742 <td valign="top">blur</td>
743 <td valign="top">Arguments:
744 <em class="arg">Width</em>[x<em class="arg">Height</em
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]745 >[+<em class="arg">Angle</em>][+<em class="arg">Angle2</em>]]
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]746 <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]747 <br>A Variable Blur Mapping Composition method, where each pixel in the
748 overlaid region is replaced with an Elliptical Weighted Average (EWA),
749 with an ellipse (typically a circle) of the given sigma size, scaled
750 according to overlay (source image) grayscale mapping.
751 <br><br>
752 As per 'Displace' and 'Distort', the red channel will modulate the
753 width of the ellipse, while the green channel will modulate the height
cristy075ad252010-10-30 21:56:17 +0000[diff] [blame]754 of the ellipse. If a single Angle value is given in the arguments,
755 then the ellipse will then be rotated by the angle specifed.
756 <br><br>
757 Normally the blue channel of the mapping overlay image is ignored.
758 However if a second ellipse angle is given, then it is assumed that
759 the blue channel defines a variable angle for the ellipse ranging from
760 the first angle to the second angle given. This allows to generate
761 radial blurs, or a rough approximation for rotational blur. Or any mix
762 of the two.
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]763 <br><br>
764 Added to ImageMagick version 6.5.4-0.
765 </td>
766 </tr>
767
768 </tbody>
769</table>
770
771<p>To print a complete list of all the available compose operators, use <a
cristyabd337d2010-08-17 01:06:59 +0000[diff] [blame]772href="../www/command-line-options.html#list">-list compose</a>.</p>
cristybc9539a2010-08-16 18:06:20 +0000[diff] [blame]773
774
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