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   CHAPTER 4                                                                  Graphics



   should not reference the PostScript definitions corresponding to PDF procedure
   sets (see Section 10.1, “Procedure Sets”), which are subject to change.


4.8 Images

   PDF’s painting operators include general facilities for dealing with sampled im-
   ages. A sampled image (or just image for short) is a rectangular array of sample
   values, each representing a color. The image may approximate the appearance of
   some natural scene obtained through an input scanner or a video camera, or it
   may be generated synthetically.




                            FIGURE 4.25 Typical sampled image


   An image is defined by a sequence of samples obtained by scanning the image
   array in row or column order. Each sample in the array consists of as many color
   components as are needed for the color space in which they are specified—for
   example, one component for DeviceGray, three for DeviceRGB, four for
   DeviceCMYK, or whatever number is required by a particular DeviceN space.
   Each component is a 1-, 2-, 4-, 8-, or (in PDF 1.5) 16-bit integer, permitting the
   representation of 2, 4, 16, 256, or (in PDF 1.5) 65536 distinct values for each com-
   ponent. (Other component sizes can be accommodated when a JPXDecode filter
   is used; see Section 3.3.8, “JPXDecode Filter.)

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