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      SECTION 4.5                                                             Color Spaces



4.5.2 Color Space Families

      Color spaces can be classified into color space families. Spaces within a family
      share the same general characteristics; they are distinguished by parameter values
      supplied at the time the space is specified. The families fall into three broad cate-
      gories:

      • Device color spaces directly specify colors or shades of gray that the output
        device is to produce. They provide a variety of color specification methods,
        including grayscale, RGB (red-green-blue), and CMYK (cyan-magenta-yellow-
        black), corresponding to the color space families DeviceGray, DeviceRGB, and
        DeviceCMYK. Since each of these families consists of just a single color space
        with no parameters, they are often loosely referred to as the DeviceGray,
        DeviceRGB, and DeviceCMYK color spaces.
      • CIE-based color spaces are based on an international standard for color specifi-
        cation created by the Commission Internationale de l’Éclairage (International
        Commission on Illumination). These spaces specify colors in a way that is in-
        dependent of the characteristics of any particular output device. Color space
        families in this category include CalGray, CalRGB, Lab, and ICCBased. Individu-
        al color spaces within these families are specified by means of dictionaries con-
        taining the parameter values needed to define the space.
      • Special color spaces add features or properties to an underlying color space.
        They include facilities for patterns, color mapping, separations, and high-
        fidelity and multitone color. The corresponding color space families are
        Pattern, Indexed, Separation, and DeviceN. Individual color spaces within
        these families are specified by means of additional parameters.

      Table 4.12 summarizes the color space families supported by PDF. (See imple-
      mentation note 47 in Appendix H.)

                                TABLE 4.12 Color space families
      DEVICE                         CIE-BASED                     SPECIAL

      DeviceGray (PDF 1.1)           CalGray (PDF 1.1)             Indexed (PDF 1.1)

      DeviceRGB (PDF 1.1)            CalRGB (PDF 1.1)              Pattern (PDF 1.2)

      DeviceCMYK (PDF 1.1)           Lab (PDF 1.1)                 Separation (PDF 1.2)

                                     ICCBased (PDF 1.3)            DeviceN (PDF 1.3)

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