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197<div class="main">
198
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]199<h1>Module enhance Methods</h1>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]200<p class="navigation-index">[<a href="#AutoGammaImage">AutoGammaImage</a> &bull; <a href="#AutoLevelImage">AutoLevelImage</a> &bull; <a href="#Use BrightnessContrastImage">Use BrightnessContrastImage</a> &bull; <a href="#ColorDecisionListImage">ColorDecisionListImage</a> &bull; <a href="#ClutImage">ClutImage</a> &bull; <a href="#ContrastImage">ContrastImage</a> &bull; <a href="#The ContrastStretchImage">The ContrastStretchImage</a> &bull; <a href="#EnhanceImage">EnhanceImage</a> &bull; <a href="#EqualizeImage">EqualizeImage</a> &bull; <a href="#GammaImage">GammaImage</a> &bull; <a href="#HaldClutImage">HaldClutImage</a> &bull; <a href="#LevelImage">LevelImage</a> &bull; <a href="#LevelizeImage">LevelizeImage</a> &bull; <a href="#LevelizeImageChannel">LevelizeImageChannel</a> &bull; <a href="#LevelImageColor">LevelImageColor</a> &bull; <a href="#The LinearStretchImage">The LinearStretchImage</a> &bull; <a href="#ModulateImage">ModulateImage</a> &bull; <a href="#NegateImage">NegateImage</a> &bull; <a href="#The NormalizeImage">The NormalizeImage</a> &bull; <a href="#SigmoidalContrastImage">SigmoidalContrastImage</a>]</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]201
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]202<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="AutoGammaImage">AutoGammaImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]203<div class="doc-section">
204
205<p>AutoGammaImage() extract the 'mean' from the image and adjust the image to try make set its gamma appropriatally.</p>
206
207<p>The format of the AutoGammaImage method is:</p>
208
209<pre class="code">
210 MagickBooleanType AutoGammaImage(Image *image)
211 MagickBooleanType AutoGammaImageChannel(Image *image,
212 const ChannelType channel)
213</pre>
214
215<p>A description of each parameter follows:</p>
216
217<h5>image</h5>
218<p>The image to auto-level</p>
219
220<h5>channel</h5>
221<p>The channels to auto-level. If the special 'SyncChannels' flag is set all given channels is adjusted in the same way using the mean average of those channels.</p>
222
223 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]224<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="AutoLevelImage">AutoLevelImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]225<div class="doc-section">
226
227<p>AutoLevelImage() adjusts the levels of a particular image channel by scaling the minimum and maximum values to the full quantum range.</p>
228
229<p>The format of the LevelImage method is:</p>
230
231<pre class="code">
232 MagickBooleanType AutoLevelImage(Image *image)
233 MagickBooleanType AutoLevelImageChannel(Image *image,
234 const ChannelType channel)
235</pre>
236
237<p>A description of each parameter follows:</p>
238
239<h5>image</h5>
240<p>The image to auto-level</p>
241
242<h5>channel</h5>
243<p>The channels to auto-level. If the special 'SyncChannels' flag is set the min/max/mean value of all given channels is used for all given channels, to all channels in the same way.</p>
244
245 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]246<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="Use_BrightnessContrastImage">Use BrightnessContrastImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]247<div class="doc-section">
248
249<p>Use BrightnessContrastImage() to change the brightness and/or contrast of an image. It converts the brightness and contrast parameters into slope and intercept and calls a polynomical function to apply to the image.</p>
250
251<p>The format of the BrightnessContrastImage method is:</p>
252
253<pre class="code">
254 MagickBooleanType BrightnessContrastImage(Image *image,
255 const double brightness,const double contrast)
256 MagickBooleanType BrightnessContrastImageChannel(Image *image,
257 const ChannelType channel,const double brightness,
258 const double contrast)
259</pre>
260
261<p>A description of each parameter follows:</p>
262
263<h5>image</h5>
264<p>the image.</p>
265
266<h5>channel</h5>
267<p>the channel.</p>
268
269<h5>brightness</h5>
270<p>the brightness percent (-100 .. 100).</p>
271
272<h5>contrast</h5>
273<p>the contrast percent (-100 .. 100).</p>
274
275 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]276<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="ColorDecisionListImage">ColorDecisionListImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]277<div class="doc-section">
278
279<p>ColorDecisionListImage() accepts a lightweight Color Correction Collection (CCC) file which solely contains one or more color corrections and applies the correction to the image. Here is a sample CCC file:</p>
280
281<pre class="text">
282 <ColorCorrectionCollection xmlns="urn:ASC:CDL:v1.2">
283 <ColorCorrection id="cc03345">
284 <SOPNode>
285 <Slope> 0.9 1.2 0.5 </Slope>
286 <Offset> 0.4 -0.5 0.6 </Offset>
287 <Power> 1.0 0.8 1.5 </Power>
288 </SOPNode>
289 <SATNode>
290 <Saturation> 0.85 </Saturation>
291 </SATNode>
292 </ColorCorrection>
293 </ColorCorrectionCollection>
294</pre>
295
296<p>which includes the slop, offset, and power for each of the RGB channels as well as the saturation.</p>
297
298<p>The format of the ColorDecisionListImage method is:</p>
299
300<pre class="code">
301 MagickBooleanType ColorDecisionListImage(Image *image,
302 const char *color_correction_collection)
303</pre>
304
305<p>A description of each parameter follows:</p>
306
307<h5>image</h5>
308<p>the image.</p>
309
310<h5>color_correction_collection</h5>
311<p>the color correction collection in XML.</p>
312
313 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]314<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="ClutImage">ClutImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]315<div class="doc-section">
316
317<p>ClutImage() replaces each color value in the given image, by using it as an index to lookup a replacement color value in a Color Look UP Table in the form of an image. The values are extracted along a diagonal of the CLUT image so either a horizontal or vertial gradient image can be used.</p>
318
319<p>Typically this is used to either re-color a gray-scale image according to a color gradient in the CLUT image, or to perform a freeform histogram (level) adjustment according to the (typically gray-scale) gradient in the CLUT image.</p>
320
321<p>When the 'channel' mask includes the matte/alpha transparency channel but one image has no such channel it is assumed that that image is a simple gray-scale image that will effect the alpha channel values, either for gray-scale coloring (with transparent or semi-transparent colors), or a histogram adjustment of existing alpha channel values. If both images have matte channels, direct and normal indexing is applied, which is rarely used.</p>
322
323<p>The format of the ClutImage method is:</p>
324
325<pre class="code">
326 MagickBooleanType ClutImage(Image *image,Image *clut_image)
327 MagickBooleanType ClutImageChannel(Image *image,
328 const ChannelType channel,Image *clut_image)
329</pre>
330
331<p>A description of each parameter follows:</p>
332
333<h5>image</h5>
334<p>the image, which is replaced by indexed CLUT values</p>
335
336<h5>clut_image</h5>
337<p>the color lookup table image for replacement color values.</p>
338
339<h5>channel</h5>
340<p>the channel.</p>
341
342 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]343<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="ContrastImage">ContrastImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]344<div class="doc-section">
345
346<p>ContrastImage() enhances the intensity differences between the lighter and darker elements of the image. Set sharpen to a MagickTrue to increase the image contrast otherwise the contrast is reduced.</p>
347
348<p>The format of the ContrastImage method is:</p>
349
350<pre class="code">
351 MagickBooleanType ContrastImage(Image *image,
352 const MagickBooleanType sharpen)
353</pre>
354
355<p>A description of each parameter follows:</p>
356
357<h5>image</h5>
358<p>the image.</p>
359
360<h5>sharpen</h5>
361<p>Increase or decrease image contrast.</p>
362
363 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]364<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="The_ContrastStretchImage">The ContrastStretchImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]365<div class="doc-section">
366
367<p>The ContrastStretchImage() is a simple image enhancement technique that attempts to improve the contrast in an image by `stretching' the range of intensity values it contains to span a desired range of values. It differs from the more sophisticated histogram equalization in that it can only apply a linear scaling function to the image pixel values. As a result the `enhancement' is less harsh.</p>
368
369<p>The format of the ContrastStretchImage method is:</p>
370
371<pre class="code">
372 MagickBooleanType ContrastStretchImage(Image *image,
373 const char *levels)
374 MagickBooleanType ContrastStretchImageChannel(Image *image,
375 const size_t channel,const double black_point,
376 const double white_point)
377</pre>
378
379<p>A description of each parameter follows:</p>
380
381<h5>image</h5>
382<p>the image.</p>
383
384<h5>channel</h5>
385<p>the channel.</p>
386
387<h5>black_point</h5>
388<p>the black point.</p>
389
390<h5>white_point</h5>
391<p>the white point.</p>
392
393<h5>levels</h5>
394<p>Specify the levels where the black and white points have the range of 0 to number-of-pixels (e.g. 1, 10x90, etc.).</p>
395
396 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]397<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="EnhanceImage">EnhanceImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]398<div class="doc-section">
399
400<p>EnhanceImage() applies a digital filter that improves the quality of a noisy image.</p>
401
402<p>The format of the EnhanceImage method is:</p>
403
404<pre class="code">
405 Image *EnhanceImage(const Image *image,ExceptionInfo *exception)
406</pre>
407
408<p>A description of each parameter follows:</p>
409
410<h5>image</h5>
411<p>the image.</p>
412
413<h5>exception</h5>
414<p>return any errors or warnings in this structure.</p>
415
416 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]417<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="EqualizeImage">EqualizeImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]418<div class="doc-section">
419
420<p>EqualizeImage() applies a histogram equalization to the image.</p>
421
422<p>The format of the EqualizeImage method is:</p>
423
424<pre class="code">
425 MagickBooleanType EqualizeImage(Image *image)
426 MagickBooleanType EqualizeImageChannel(Image *image,
427 const ChannelType channel)
428</pre>
429
430<p>A description of each parameter follows:</p>
431
432<h5>image</h5>
433<p>the image.</p>
434
435<h5>channel</h5>
436<p>the channel.</p>
437
438 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]439<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="GammaImage">GammaImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]440<div class="doc-section">
441
442<p>GammaImage() gamma-corrects a particular image channel. The same image viewed on different devices will have perceptual differences in the way the image's intensities are represented on the screen. Specify individual gamma levels for the red, green, and blue channels, or adjust all three with the gamma parameter. Values typically range from 0.8 to 2.3.</p>
443
444<p>You can also reduce the influence of a particular channel with a gamma value of 0.</p>
445
446<p>The format of the GammaImage method is:</p>
447
448<pre class="code">
449 MagickBooleanType GammaImage(Image *image,const double gamma)
450 MagickBooleanType GammaImageChannel(Image *image,
451 const ChannelType channel,const double gamma)
452</pre>
453
454<p>A description of each parameter follows:</p>
455
456<h5>image</h5>
457<p>the image.</p>
458
459<h5>channel</h5>
460<p>the channel.</p>
461
462<h5>gamma</h5>
463<p>the image gamma.</p>
464
465 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]466<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="HaldClutImage">HaldClutImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]467<div class="doc-section">
468
469<p>HaldClutImage() applies a Hald color lookup table to the image. A Hald color lookup table is a 3-dimensional color cube mapped to 2 dimensions. Create it with the HALD coder. You can apply any color transformation to the Hald image and then use this method to apply the transform to the image.</p>
470
471<p>The format of the HaldClutImage method is:</p>
472
473<pre class="code">
474 MagickBooleanType HaldClutImage(Image *image,Image *hald_image)
475 MagickBooleanType HaldClutImageChannel(Image *image,
476 const ChannelType channel,Image *hald_image)
477</pre>
478
479<p>A description of each parameter follows:</p>
480
481<h5>image</h5>
482<p>the image, which is replaced by indexed CLUT values</p>
483
484<h5>hald_image</h5>
485<p>the color lookup table image for replacement color values.</p>
486
487<h5>channel</h5>
488<p>the channel.</p>
489
490 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]491<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="LevelImage">LevelImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]492<div class="doc-section">
493
494<p>LevelImage() adjusts the levels of a particular image channel by scaling the colors falling between specified white and black points to the full available quantum range.</p>
495
496<p>The parameters provided represent the black, and white points. The black point specifies the darkest color in the image. Colors darker than the black point are set to zero. White point specifies the lightest color in the image. Colors brighter than the white point are set to the maximum quantum value.</p>
497
498<p>If a '!' flag is given, map black and white colors to the given levels rather than mapping those levels to black and white. See LevelizeImageChannel() and LevelizeImageChannel(), below.</p>
499
500<p>Gamma specifies a gamma correction to apply to the image.</p>
501
502<p>The format of the LevelImage method is:</p>
503
504<pre class="code">
505 MagickBooleanType LevelImage(Image *image,const char *levels)
506</pre>
507
508<p>A description of each parameter follows:</p>
509
510<h5>image</h5>
511<p>the image.</p>
512
513<h5>levels</h5>
514<p>Specify the levels where the black and white points have the range of 0-QuantumRange, and gamma has the range 0-10 (e.g. 10x90+2). A '!' flag inverts the re-mapping.</p>
515
516 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]517<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="LevelizeImage">LevelizeImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]518<div class="doc-section">
519
520<p>LevelizeImage() applies the normal level operation to the image, spreading out the values between the black and white points over the entire range of values. Gamma correction is also applied after the values has been mapped.</p>
521
522<p>It is typically used to improve image contrast, or to provide a controlled linear threshold for the image. If the black and white points are set to the minimum and maximum values found in the image, the image can be normalized. or by swapping black and white values, negate the image.</p>
523
524<p>The format of the LevelizeImage method is:</p>
525
526<pre class="code">
527 MagickBooleanType LevelizeImage(Image *image,const double black_point,
528 const double white_point,const double gamma)
529 MagickBooleanType LevelizeImageChannel(Image *image,
530 const ChannelType channel,const double black_point,
531 const double white_point,const double gamma)
532</pre>
533
534<p>A description of each parameter follows:</p>
535
536<h5>image</h5>
537<p>the image.</p>
538
539<h5>channel</h5>
540<p>the channel.</p>
541
542<h5>black_point</h5>
543<p>The level which is to be mapped to zero (black)</p>
544
545<h5>white_point</h5>
546<p>The level which is to be mapped to QuantiumRange (white)</p>
547
548<h5>gamma</h5>
549<p>adjust gamma by this factor before mapping values. use 1.0 for purely linear stretching of image color values</p>
550
551 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]552<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="LevelizeImageChannel">LevelizeImageChannel</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]553<div class="doc-section">
554
555<p>LevelizeImageChannel() applies the reversed LevelImage() operation to just the specific channels specified. It compresses the full range of color values, so that they lie between the given black and white points. Gamma is applied before the values are mapped.</p>
556
557<p>LevelizeImageChannel() can be called with by using a +level command line API option, or using a '!' on a -level or LevelImage() geometry string.</p>
558
559<p>It can be used for example de-contrast a greyscale image to the exact levels specified. Or by using specific levels for each channel of an image you can convert a gray-scale image to any linear color gradient, according to those levels.</p>
560
561<p>The format of the LevelizeImageChannel method is:</p>
562
563<pre class="code">
564 MagickBooleanType LevelizeImageChannel(Image *image,
565 const ChannelType channel,const char *levels)
566</pre>
567
568<p>A description of each parameter follows:</p>
569
570<h5>image</h5>
571<p>the image.</p>
572
573<h5>channel</h5>
574<p>the channel.</p>
575
576<h5>black_point</h5>
577<p>The level to map zero (black) to.</p>
578
579<h5>white_point</h5>
580<p>The level to map QuantiumRange (white) to.</p>
581
582<h5>gamma</h5>
583<p>adjust gamma by this factor before mapping values.</p>
584
585 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]586<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="LevelImageColor">LevelImageColor</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]587<div class="doc-section">
588
cristybe3c5be2011-03-05 17:35:07 +0000[diff] [blame]589<p>LevelImageColor() maps the given color to "black" and "white" values, linearly spreading out the colors, and level values on a channel by channel bases, as per LevelImage(). The given colors allows you to specify different level ranges for each of the color channels separately.</p>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]590
591<p>If the boolean 'invert' is set true the image values will modifyed in the reverse direction. That is any existing "black" and "white" colors in the image will become the color values given, with all other values compressed appropriatally. This effectivally maps a greyscale gradient into the given color gradient.</p>
592
593<p>The format of the LevelColorsImageChannel method is:</p>
594
595<pre class="code">
596 MagickBooleanType LevelColorsImage(Image *image,
597 const MagickPixelPacket *black_color,
598 const MagickPixelPacket *white_color,const MagickBooleanType invert)
599 MagickBooleanType LevelColorsImageChannel(Image *image,
600 const ChannelType channel,const MagickPixelPacket *black_color,
601 const MagickPixelPacket *white_color,const MagickBooleanType invert)
602</pre>
603
604<p>A description of each parameter follows:</p>
605
606<h5>image</h5>
607<p>the image.</p>
608
609<h5>channel</h5>
610<p>the channel.</p>
611
612<h5>black_color</h5>
613<p>The color to map black to/from</p>
614
615<h5>white_point</h5>
616<p>The color to map white to/from</p>
617
618<h5>invert</h5>
619<p>if true map the colors (levelize), rather than from (level)</p>
620
621 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]622<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="The_LinearStretchImage">The LinearStretchImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]623<div class="doc-section">
624
625<p>The LinearStretchImage() discards any pixels below the black point and above the white point and levels the remaining pixels.</p>
626
627<p>The format of the LinearStretchImage method is:</p>
628
629<pre class="code">
630 MagickBooleanType LinearStretchImage(Image *image,
631 const double black_point,const double white_point)
632</pre>
633
634<p>A description of each parameter follows:</p>
635
636<h5>image</h5>
637<p>the image.</p>
638
639<h5>black_point</h5>
640<p>the black point.</p>
641
642<h5>white_point</h5>
643<p>the white point.</p>
644
645 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]646<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="ModulateImage">ModulateImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]647<div class="doc-section">
648
649<p>ModulateImage() lets you control the brightness, saturation, and hue of an image. Modulate represents the brightness, saturation, and hue as one parameter (e.g. 90,150,100). If the image colorspace is HSL, the modulation is lightness, saturation, and hue. And if the colorspace is HWB, use blackness, whiteness, and hue.</p>
650
651<p>The format of the ModulateImage method is:</p>
652
653<pre class="code">
654 MagickBooleanType ModulateImage(Image *image,const char *modulate)
655</pre>
656
657<p>A description of each parameter follows:</p>
658
659<h5>image</h5>
660<p>the image.</p>
661
662<h5>modulate</h5>
663<p>Define the percent change in brightness, saturation, and hue.</p>
664
665 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]666<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="NegateImage">NegateImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]667<div class="doc-section">
668
669<p>NegateImage() negates the colors in the reference image. The grayscale option means that only grayscale values within the image are negated.</p>
670
671<p>The format of the NegateImageChannel method is:</p>
672
673<pre class="code">
674 MagickBooleanType NegateImage(Image *image,
675 const MagickBooleanType grayscale)
676 MagickBooleanType NegateImageChannel(Image *image,
677 const ChannelType channel,const MagickBooleanType grayscale)
678</pre>
679
680<p>A description of each parameter follows:</p>
681
682<h5>image</h5>
683<p>the image.</p>
684
685<h5>channel</h5>
686<p>the channel.</p>
687
688<h5>grayscale</h5>
689<p>If MagickTrue, only negate grayscale pixels within the image.</p>
690
691 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]692<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="The_NormalizeImage">The NormalizeImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]693<div class="doc-section">
694
695<p>The NormalizeImage() method enhances the contrast of a color image by mapping the darkest 2 percent of all pixel to black and the brightest 1 percent to white.</p>
696
697<p>The format of the NormalizeImage method is:</p>
698
699<pre class="code">
700 MagickBooleanType NormalizeImage(Image *image)
701 MagickBooleanType NormalizeImageChannel(Image *image,
702 const ChannelType channel)
703</pre>
704
705<p>A description of each parameter follows:</p>
706
707<h5>image</h5>
708<p>the image.</p>
709
710<h5>channel</h5>
711<p>the channel.</p>
712
713 </div>
cristy350dea42011-02-15 17:31:04 +0000[diff] [blame]714<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance_8c.html" id="SigmoidalContrastImage">SigmoidalContrastImage</a></h2>
cristy6f77f692011-02-15 15:31:39 +0000[diff] [blame]715<div class="doc-section">
716
717<p>SigmoidalContrastImage() adjusts the contrast of an image with a non-linear sigmoidal contrast algorithm. Increase the contrast of the image using a sigmoidal transfer function without saturating highlights or shadows. Contrast indicates how much to increase the contrast (0 is none; 3 is typical; 20 is pushing it); mid-point indicates where midtones fall in the resultant image (0 is white; 50 is middle-gray; 100 is black). Set sharpen to MagickTrue to increase the image contrast otherwise the contrast is reduced.</p>
718
719<p>The format of the SigmoidalContrastImage method is:</p>
720
721<pre class="code">
722 MagickBooleanType SigmoidalContrastImage(Image *image,
723 const MagickBooleanType sharpen,const char *levels)
724 MagickBooleanType SigmoidalContrastImageChannel(Image *image,
725 const ChannelType channel,const MagickBooleanType sharpen,
726 const double contrast,const double midpoint)
727</pre>
728
729<p>A description of each parameter follows:</p>
730
731<h5>image</h5>
732<p>the image.</p>
733
734<h5>channel</h5>
735<p>the channel.</p>
736
737<h5>sharpen</h5>
738<p>Increase or decrease image contrast.</p>
739
740<h5>alpha</h5>
741<p>strength of the contrast, the larger the number the more 'threshold-like' it becomes.</p>
742
743<h5>beta</h5>
744<p>midpoint of the function as a color value 0 to QuantumRange.</p>
745
746 </div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]747
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