ImageMagick: MagickCore, C API for ImageMagick: Enhance an Image
Author: ImageMagick Studio LLC
Description: ImageMagick® is a software suite to create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (about 100) including GIF, JPEG, JPEG-2000, PNG, PDF, PhotoCD, TIFF, and DPX. Use ImageMagick to translate, flip, mirror, rotate, scale, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves. ImageMagick is free software delivered as a ready-to-run binary distribution or as source code that you can freely use, copy, modify, and distribute. Its license is compatible with the GPL. It runs on all major operating systems. The functionality of ImageMagick is typically utilized from the command line or you can use the features from programs written in your favorite programming language. Choose from these interfaces: MagickCore (C), MagickWand (C), ChMagick (Ch), Magick++ (C++), JMagick (Java), L-Magick (Lisp), PascalMagick (Pascal), PerlMagick (Perl), MagickWand for PHP (P [cell cut: 1167 characters, first 1000 kept]
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## ContrastImage 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. The format of the ContrastImage method is:
      MagickBooleanType ContrastImage(Image *image,
        const MagickBooleanType sharpen)
A description of each parameter follows: ##### image The image. ##### sharpen Increase or decrease image contrast. ## The ContrastStretchImage 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. The format of the ContrastStretchImage method is:
      MagickBooleanType ContrastStretchImage(Image *image,
        const char *levels)
      MagickBooleanType ContrastStretchImageChannel(Image *image,
        const unsigned long channel,const double black_point,
        const double white_point)
A description of each parameter follows: ##### image The image. ##### channel The channel. ##### black_point The black point. ##### white_point The white point. ##### levels Specify the levels where the black and white points have the range of 0 to number-of-pixels (e.g. 1, 10x90, etc.). ## EnhanceImage EnhanceImage() applies a digital filter that improves the quality of a noisy image. The format of the EnhanceImage method is:
      Image *EnhanceImage(const Image *image,ExceptionInfo *exception)
A description of each parameter follows: ##### image The image. ##### exception Return any errors or warnings in this structure. ## EqualizeImage EqualizeImage() applies a histogram equalization to the image. The format of the EqualizeImage method is:
      MagickBooleanType EqualizeImage(Image *image)
A description of each parameter follows: ##### image The image. ## GammaImage 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. You can also reduce the influence of a particular channel with a gamma value of 0. The format of the GammaImage method is:
      MagickBooleanType GammaImage(Image *image,const double gamma)
      MagickBooleanType GammaImageChannel(Image *image,
        const ChannelType channel,const double gamma)
A description of each parameter follows: ##### image The image. ##### channel The channel. ##### gamma The image gamma. ## LevelImage 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. The parameters provided represent the black, mid, and white points. The black point specifies the darkest color in the image. Colors darker than the black point are set to zero. Gamma specifies a gamma correction to apply to the image. White point specifies the lightest color in the image. Colors brighter than the white point are set to the maximum quantum value. The format of the LevelImage method is:
      MagickBooleanType LevelImage(Image *image,const char *levels)
      MagickBooleanType LevelImageChannel(Image *image,
        const ChannelType channel,const char *levels)
A description of each parameter follows: ##### image The image. ##### channel The channel. ##### levels 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). ## The LinearStretchImage The LinearStretchImage() discards any pixels below the black point and above the white point and levels the remaining pixels. The format of the LinearStretchImage method is:
      MagickBooleanType LinearStretchImage(Image *image,
        const double black_point,const double white_point)
A description of each parameter follows: ##### image The image. ##### black_point The black point. ##### white_point The white point. ## ModulateImage 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 luminosity, saturation, and hue. And if the colorspace is HWB, use blackness, whiteness, and hue. The format of the ModulateImage method is:
      MagickBooleanType ModulateImage(Image *image,const char *modulate)
A description of each parameter follows: ##### image The image. ##### modulate Define the percent change in brightness, saturation, and hue. ## NegateImage NegateImage() negates the colors in the reference image. The grayscale option means that only grayscale values within the image are negated. The format of the NegateImageChannel method is:
      MagickBooleanType NegateImage(Image *image,
        const MagickBooleanType grayscale)
      MagickBooleanType NegateImageChannel(Image *image,
        const ChannelType channel,const MagickBooleanType grayscale)
A description of each parameter follows: ##### image The image. ##### channel The channel. ##### grayscale If MagickTrue, only negate grayscale pixels within the image. ## The NormalizeImage 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. The format of the NormalizeImage method is:
      MagickBooleanType NormalizeImage(Image *image,
        const unsigned long channel)
A description of each parameter follows: ##### image The image. ##### channel The channel. ## SigmoidalContrastImage 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. The format of the SigmoidalContrastImage method is:
      MagickBooleanType SigmoidalContrastImage(Image *image,
        const MagickBooleanType sharpen,const char *levels)
      MagickBooleanType SigmoidalContrastImageChannel(Image *image,
        const ChannelType channel,const MagickBooleanType sharpen,
        const double contrast,const double midpoint)
A description of each parameter follows: ##### image The image. ##### channel The channel. ##### sharpen Increase or decrease image contrast. ##### contrast control the "shoulder" of the contast curve. ##### midpoint control the "toe" of the contast curve. |

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