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