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12 <title>ImageMagick: MagickCore, C API for ImageMagick: Enhance an Image</title>
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147
148</div>
149
150<div class="main">
151
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]152<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]153
154<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
155_8c.html" target="source" name="AutoGammaImage">AutoGammaImage</a></h2>
156<div class="doc-section">
157
158<p>AutoGammaImage() extract the 'mean' from the image and adjust the image to try make set its gamma appropriatally.</p></ol>
159
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]160<p>The format of the AutoGammaImage method is:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]161
162<pre class="code">
163 MagickBooleanType AutoGammaImage(Image *image)
164 MagickBooleanType AutoGammaImageChannel(Image *image,
165 const ChannelType channel)
166</pre>
167
168<p>A description of each parameter follows:</p></ol>
169
170<h5>image</h5>
171<ol><p>The image to auto-level</p></ol>
172
173<h5>channel</h5>
174<ol><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></ol>
175
176 </div>
177<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
178_8c.html" target="source" name="AutoLevelImage">AutoLevelImage</a></h2>
179<div class="doc-section">
180
181<p>AutoLevelImage() adjusts the levels of a particular image channel by scaling the minimum and maximum values to the full quantum range.</p></ol>
182
183<p>The format of the LevelImage method is:</p>
184
185<pre class="code">
186 MagickBooleanType AutoLevelImage(Image *image)
187 MagickBooleanType AutoLevelImageChannel(Image *image,
188 const ChannelType channel)
189</pre>
190
191<p>A description of each parameter follows:</p></ol>
192
193<h5>image</h5>
194<ol><p>The image to auto-level</p></ol>
195
196<h5>channel</h5>
197<ol><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></ol>
198
199 </div>
200<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
cristy16ff93c2010-01-13 23:18:07 +0000[diff] [blame]201_8c.html" target="source" name="Use BrightnessContrastImage">Use BrightnessContrastImage</a></h2>
202<div class="doc-section">
203
204<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></ol>
205
206<p>The format of the BrightnessContrastImage method is:</p>
207
208<pre class="code">
209 MagickBooleanType BrightnessContrastImage(Image *image,
210 const double brightness,const double contrast)
211 MagickBooleanType BrightnessContrastImageChannel(Image *image,
212 const ChannelType channel,const double brightness,
213 const double contrast)
214</pre>
215
216<p>A description of each parameter follows:</p></ol>
217
218<h5>image</h5>
219<ol><p>the image.</p></ol>
220
221<h5>channel</h5>
222<ol><p>the channel.</p></ol>
223
224<h5>brightness</h5>
225<ol><p>the brightness percent (-100 .. 100).</p></ol>
226
227<h5>contrast</h5>
228<ol><p>the contrast percent (-100 .. 100).</p></ol>
229
230 </div>
231<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]232_8c.html" target="source" name="ColorDecisionListImage">ColorDecisionListImage</a></h2>
233<div class="doc-section">
234
235<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>
236
237<pre class="text">
238 <ColorCorrectionCollection xmlns="urn:ASC:CDL:v1.2">
239 <ColorCorrection id="cc03345">
240 <SOPNode>
241 <Slope> 0.9 1.2 0.5 </Slope>
242 <Offset> 0.4 -0.5 0.6 </Offset>
243 <Power> 1.0 0.8 1.5 </Power>
244 </SOPNode>
245 <SATNode>
246 <Saturation> 0.85 </Saturation>
247 </SATNode>
248 </ColorCorrection>
249 </ColorCorrectionCollection>
250</pre>
251
252<p>which includes the slop, offset, and power for each of the RGB channels as well as the saturation.</p></ol>
253
254<p>The format of the ColorDecisionListImage method is:</p>
255
256<pre class="code">
257 MagickBooleanType ColorDecisionListImage(Image *image,
258 const char *color_correction_collection)
259</pre>
260
261<p>A description of each parameter follows:</p></ol>
262
263<h5>image</h5>
264<ol><p>the image.</p></ol>
265
266<h5>color_correction_collection</h5>
267<ol><p>the color correction collection in XML.</p></ol>
268
269 </div>
270<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
271_8c.html" target="source" name="ClutImage">ClutImage</a></h2>
272<div class="doc-section">
273
cristyeaedf062010-05-29 22:36:02 +0000[diff] [blame^]274<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></ol>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]275
276<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></ol>
277
278<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></ol>
279
280<p>The format of the ClutImage method is:</p>
281
282<pre class="code">
283 MagickBooleanType ClutImage(Image *image,Image *clut_image)
284 MagickBooleanType ClutImageChannel(Image *image,
285 const ChannelType channel,Image *clut_image)
286</pre>
287
288<p>A description of each parameter follows:</p></ol>
289
290<h5>image</h5>
291<ol><p>the image, which is replaced by indexed CLUT values</p></ol>
292
293<h5>clut_image</h5>
294<ol><p>the color lookup table image for replacement color values.</p></ol>
295
296<h5>channel</h5>
297<ol><p>the channel.</p></ol>
298
299 </div>
300<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
301_8c.html" target="source" name="ContrastImage">ContrastImage</a></h2>
302<div class="doc-section">
303
304<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></ol>
305
306<p>The format of the ContrastImage method is:</p>
307
308<pre class="code">
309 MagickBooleanType ContrastImage(Image *image,
310 const MagickBooleanType sharpen)
311</pre>
312
313<p>A description of each parameter follows:</p></ol>
314
315<h5>image</h5>
316<ol><p>the image.</p></ol>
317
318<h5>sharpen</h5>
319<ol><p>Increase or decrease image contrast.</p></ol>
320
321 </div>
322<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
323_8c.html" target="source" name="The ContrastStretchImage">The ContrastStretchImage</a></h2>
324<div class="doc-section">
325
326<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></ol>
327
328<p>The format of the ContrastStretchImage method is:</p>
329
330<pre class="code">
331 MagickBooleanType ContrastStretchImage(Image *image,
332 const char *levels)
333 MagickBooleanType ContrastStretchImageChannel(Image *image,
cristybb503372010-05-27 20:51:26 +0000[diff] [blame]334 const size_t channel,const double black_point,
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]335 const double white_point)
336</pre>
337
338<p>A description of each parameter follows:</p></ol>
339
340<h5>image</h5>
341<ol><p>the image.</p></ol>
342
343<h5>channel</h5>
344<ol><p>the channel.</p></ol>
345
346<h5>black_point</h5>
347<ol><p>the black point.</p></ol>
348
349<h5>white_point</h5>
350<ol><p>the white point.</p></ol>
351
352<h5>levels</h5>
353<ol><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></ol>
354
355 </div>
356<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
357_8c.html" target="source" name="EnhanceImage">EnhanceImage</a></h2>
358<div class="doc-section">
359
360<p>EnhanceImage() applies a digital filter that improves the quality of a noisy image.</p></ol>
361
362<p>The format of the EnhanceImage method is:</p>
363
364<pre class="code">
365 Image *EnhanceImage(const Image *image,ExceptionInfo *exception)
366</pre>
367
368<p>A description of each parameter follows:</p></ol>
369
370<h5>image</h5>
371<ol><p>the image.</p></ol>
372
373<h5>exception</h5>
374<ol><p>return any errors or warnings in this structure.</p></ol>
375
376 </div>
377<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
378_8c.html" target="source" name="EqualizeImage">EqualizeImage</a></h2>
379<div class="doc-section">
380
381<p>EqualizeImage() applies a histogram equalization to the image.</p></ol>
382
383<p>The format of the EqualizeImage method is:</p>
384
385<pre class="code">
386 MagickBooleanType EqualizeImage(Image *image)
387 MagickBooleanType EqualizeImageChannel(Image *image,
388 const ChannelType channel)
389</pre>
390
391<p>A description of each parameter follows:</p></ol>
392
393<h5>image</h5>
394<ol><p>the image.</p></ol>
395
396<h5>channel</h5>
397<ol><p>the channel.</p></ol>
398
399 </div>
400<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
401_8c.html" target="source" name="GammaImage">GammaImage</a></h2>
402<div class="doc-section">
403
404<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></ol>
405
406<p>You can also reduce the influence of a particular channel with a gamma value of 0.</p></ol>
407
408<p>The format of the GammaImage method is:</p>
409
410<pre class="code">
411 MagickBooleanType GammaImage(Image *image,const double gamma)
412 MagickBooleanType GammaImageChannel(Image *image,
413 const ChannelType channel,const double gamma)
414</pre>
415
416<p>A description of each parameter follows:</p></ol>
417
418<h5>image</h5>
419<ol><p>the image.</p></ol>
420
421<h5>channel</h5>
422<ol><p>the channel.</p></ol>
423
424<h5>gamma</h5>
425<ol><p>the image gamma.</p></ol>
426
427 </div>
428<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
429_8c.html" target="source" name="HaldClutImage">HaldClutImage</a></h2>
430<div class="doc-section">
431
432<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></ol>
433
434<p>The format of the HaldClutImage method is:</p>
435
436<pre class="code">
437 MagickBooleanType HaldClutImage(Image *image,Image *hald_image)
438 MagickBooleanType HaldClutImageChannel(Image *image,
439 const ChannelType channel,Image *hald_image)
440</pre>
441
442<p>A description of each parameter follows:</p></ol>
443
444<h5>image</h5>
445<ol><p>the image, which is replaced by indexed CLUT values</p></ol>
446
447<h5>hald_image</h5>
448<ol><p>the color lookup table image for replacement color values.</p></ol>
449
450<h5>channel</h5>
451<ol><p>the channel.</p></ol>
452
453 </div>
454<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
455_8c.html" target="source" name="LevelImage">LevelImage</a></h2>
456<div class="doc-section">
457
458<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></ol>
459
460<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></ol>
461
462<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></ol>
463
464<p>Gamma specifies a gamma correction to apply to the image.</p></ol>
465
466<p>The format of the LevelImage method is:</p>
467
468<pre class="code">
469 MagickBooleanType LevelImage(Image *image,const char *levels)
470</pre>
471
472<p>A description of each parameter follows:</p></ol>
473
474<h5>image</h5>
475<ol><p>the image.</p></ol>
476
477<h5>levels</h5>
478<ol><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></ol>
479
480 </div>
481<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]482_8c.html" target="source" name="LevelizeImage">LevelizeImage</a></h2>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]483<div class="doc-section">
484
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]485<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></ol>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]486
487<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></ol>
488
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]489<p>The format of the LevelizeImage method is:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]490
491<pre class="code">
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]492 MagickBooleanType LevelizeImage(Image *image,const double black_point,
493 const double white_point,const double gamma)
494 MagickBooleanType LevelizeImageChannel(Image *image,
495 const ChannelType channel,const double black_point,
496 const double white_point,const double gamma)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]497</pre>
498
499<p>A description of each parameter follows:</p></ol>
500
501<h5>image</h5>
502<ol><p>the image.</p></ol>
503
504<h5>channel</h5>
505<ol><p>the channel.</p></ol>
506
507<h5>black_point</h5>
508<ol><p>The level which is to be mapped to zero (black)</p></ol>
509
510<h5>white_point</h5>
511<ol><p>The level which is to be mapped to QuantiumRange (white)</p></ol>
512
513<h5>gamma</h5>
514<ol><p>adjust gamma by this factor before mapping values. use 1.0 for purely linear stretching of image color values</p></ol>
515
516 </div>
517<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
518_8c.html" target="source" name="LevelizeImageChannel">LevelizeImageChannel</a></h2>
519<div class="doc-section">
520
521<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></ol>
522
523<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></ol>
524
525<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></ol>
526
527<p>The format of the LevelizeImageChannel method is:</p>
528
529<pre class="code">
530 MagickBooleanType LevelizeImageChannel(Image *image,
531 const ChannelType channel,const char *levels)
532</pre>
533
534<p>A description of each parameter follows:</p></ol>
535
536<h5>image</h5>
537<ol><p>the image.</p></ol>
538
539<h5>channel</h5>
540<ol><p>the channel.</p></ol>
541
542<h5>black_point</h5>
543<ol><p>The level to map zero (black) to.</p></ol>
544
545<h5>white_point</h5>
546<ol><p>The level to map QuantiumRange (white) to.</p></ol>
547
548<h5>gamma</h5>
549<ol><p>adjust gamma by this factor before mapping values.</p></ol>
550
551 </div>
552<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
553_8c.html" target="source" name="LevelImageColor">LevelImageColor</a></h2>
554<div class="doc-section">
555
cristye7f8fdd2009-09-20 14:43:12 +0000[diff] [blame]556<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 seperatally.</p></ol>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]557
558<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></ol>
559
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]560<p>The format of the LevelColorsImageChannel method is:</p>
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]561
562<pre class="code">
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]563 MagickBooleanType LevelColorsImage(Image *image,
cristye7f8fdd2009-09-20 14:43:12 +0000[diff] [blame]564 const MagickPixelPacket *black_color,
565 const MagickPixelPacket *white_color,const MagickBooleanType invert)
cristy5cadd612009-09-21 19:33:41 +0000[diff] [blame]566 MagickBooleanType LevelColorsImageChannel(Image *image,
567 const ChannelType channel,const MagickPixelPacket *black_color,
568 const MagickPixelPacket *white_color,const MagickBooleanType invert)
cristy3ed852e2009-09-05 21:47:34 +0000[diff] [blame]569</pre>
570
571<p>A description of each parameter follows:</p></ol>
572
573<h5>image</h5>
574<ol><p>the image.</p></ol>
575
576<h5>channel</h5>
577<ol><p>the channel.</p></ol>
578
579<h5>black_color</h5>
580<ol><p>The color to map black to/from</p></ol>
581
582<h5>white_point</h5>
583<ol><p>The color to map white to/from</p></ol>
584
585<h5>invert</h5>
586<ol><p>if true map the colors (levelize), rather than from (level)</p></ol>
587
588 </div>
589<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
590_8c.html" target="source" name="The LinearStretchImage">The LinearStretchImage</a></h2>
591<div class="doc-section">
592
593<p>The LinearStretchImage() discards any pixels below the black point and above the white point and levels the remaining pixels.</p></ol>
594
595<p>The format of the LinearStretchImage method is:</p>
596
597<pre class="code">
598 MagickBooleanType LinearStretchImage(Image *image,
599 const double black_point,const double white_point)
600</pre>
601
602<p>A description of each parameter follows:</p></ol>
603
604<h5>image</h5>
605<ol><p>the image.</p></ol>
606
607<h5>black_point</h5>
608<ol><p>the black point.</p></ol>
609
610<h5>white_point</h5>
611<ol><p>the white point.</p></ol>
612
613 </div>
614<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
615_8c.html" target="source" name="ModulateImage">ModulateImage</a></h2>
616<div class="doc-section">
617
618<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></ol>
619
620<p>The format of the ModulateImage method is:</p>
621
622<pre class="code">
623 MagickBooleanType ModulateImage(Image *image,const char *modulate)
624</pre>
625
626<p>A description of each parameter follows:</p></ol>
627
628<h5>image</h5>
629<ol><p>the image.</p></ol>
630
631<h5>modulate</h5>
632<ol><p>Define the percent change in brightness, saturation, and hue.</p></ol>
633
634 </div>
635<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
636_8c.html" target="source" name="NegateImage">NegateImage</a></h2>
637<div class="doc-section">
638
639<p>NegateImage() negates the colors in the reference image. The grayscale option means that only grayscale values within the image are negated.</p></ol>
640
641<p>The format of the NegateImageChannel method is:</p>
642
643<pre class="code">
644 MagickBooleanType NegateImage(Image *image,
645 const MagickBooleanType grayscale)
646 MagickBooleanType NegateImageChannel(Image *image,
647 const ChannelType channel,const MagickBooleanType grayscale)
648</pre>
649
650<p>A description of each parameter follows:</p></ol>
651
652<h5>image</h5>
653<ol><p>the image.</p></ol>
654
655<h5>channel</h5>
656<ol><p>the channel.</p></ol>
657
658<h5>grayscale</h5>
659<ol><p>If MagickTrue, only negate grayscale pixels within the image.</p></ol>
660
661 </div>
662<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
663_8c.html" target="source" name="The NormalizeImage">The NormalizeImage</a></h2>
664<div class="doc-section">
665
666<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></ol>
667
668<p>The format of the NormalizeImage method is:</p>
669
670<pre class="code">
671 MagickBooleanType NormalizeImage(Image *image)
672 MagickBooleanType NormalizeImageChannel(Image *image,
673 const ChannelType channel)
674</pre>
675
676<p>A description of each parameter follows:</p></ol>
677
678<h5>image</h5>
679<ol><p>the image.</p></ol>
680
681<h5>channel</h5>
682<ol><p>the channel.</p></ol>
683
684 </div>
685<h2><a href="http://www.imagemagick.org/api/MagickCore/enhance
686_8c.html" target="source" name="SigmoidalContrastImage">SigmoidalContrastImage</a></h2>
687<div class="doc-section">
688
689<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></ol>
690
691<p>The format of the SigmoidalContrastImage method is:</p>
692
693<pre class="code">
694 MagickBooleanType SigmoidalContrastImage(Image *image,
695 const MagickBooleanType sharpen,const char *levels)
696 MagickBooleanType SigmoidalContrastImageChannel(Image *image,
697 const ChannelType channel,const MagickBooleanType sharpen,
698 const double contrast,const double midpoint)
699</pre>
700
701<p>A description of each parameter follows:</p></ol>
702
703<h5>image</h5>
704<ol><p>the image.</p></ol>
705
706<h5>channel</h5>
707<ol><p>the channel.</p></ol>
708
709<h5>sharpen</h5>
710<ol><p>Increase or decrease image contrast.</p></ol>
711
712<h5>contrast</h5>
713<ol><p>control the "shoulder" of the contast curve.</p></ol>
714
715<h5>midpoint</h5>
716<ol><p>control the "toe" of the contast curve.</p></ol>
717
718 </div>
cristy3eaa0ef2010-03-06 20:35:26 +0000[diff] [blame]719
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