ImageMagick: MagickCore, C API for ImageMagick: Count the Colors in an Image
Author: ImageMagick Studio LLC
Description: ImageMagick® is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats (over 200) including PNG, JPEG, JPEG-2000, GIF, WebP, Postscript, PDF, and SVG. Use ImageMagick to resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves.
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AcquireColorCache • GetColorInfoList • GetColorList • ListColorInfo • QueryColorname

## AcquireColorCache

AcquireColorCache() caches one or more color configurations which provides a mapping between color attributes and a color name.

The format of the AcquireColorCache method is:

    LinkedListInfo *AcquireColorCache(const char *filename,
      ExceptionInfo *exception)

A description of each parameter follows:

filename
  the font file name.
exception
  return any errors or warnings in this structure.

## GetColorInfoList

GetColorInfoList() returns any colors that match the specified pattern.

The format of the GetColorInfoList function is:

    const ColorInfo **GetColorInfoList(const char *pattern,
      size_t *number_colors,ExceptionInfo *exception)

A description of each parameter follows:

pattern
  Specifies a pointer to a text string containing a pattern.
number_colors
  This integer returns the number of colors in the list.
exception
  return any errors or warnings in this structure.

## GetColorList

GetColorList() returns any colors that match the specified pattern.

The format of the GetColorList function is:

    char **GetColorList(const char *pattern,size_t *number_colors,
      ExceptionInfo *exception)

A description of each parameter follows:

pattern
  Specifies a pointer to a text string containing a pattern.
number_colors
  This integer returns the number of colors in the list.
exception
  return any errors or warnings in this structure.

## ListColorInfo

ListColorInfo() lists color names to the specified file. Color names are a convenience. Rather than defining a color by its red, green, and blue intensities just use a color name such as white, blue, or yellow.

The format of the ListColorInfo method is:

    MagickBooleanType ListColorInfo(FILE *file,ExceptionInfo *exception)

A description of each parameter follows.

file

List color names to this file handle.

exception

return any errors or warnings in this structure.

## QueryColorname

QueryColorname() returns a named color for the given color intensity. If an exact match is not found, a hex value is returned instead. For example an intensity of rgb:(0,0,0) returns black whereas rgb:(223,223,223) returns #dfdfdf.

UPDATE: the 'image' argument is no longer needed as all information should have been preset using GetPixelInfo().

The format of the QueryColorname method is:

    MagickBooleanType QueryColorname(const Image *image,
      const PixelInfo *color,const ComplianceType compliance,char *name,
      ExceptionInfo *exception)

A description of each parameter follows.

image

the image. (not used! - color gets settings from GetPixelInfo()

color

the color intensities.

Compliance

Adhere to this color standard: SVG, X11, or XPM.

name

Return the color name or hex value.

exception

return any errors or warnings in this structure.