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                                  CHAPTER 4


                              4Graphics

The graphics operators used in PDF content streams describe the appearance of
pages that are to be reproduced on a raster output device. The facilities described
in this chapter are intended for both printer and display applications.

The graphics operators form six main groups:

• Graphics state operators manipulate the data structure called the graphics state,
  the global framework within which the other graphics operators execute. The
  graphics state includes the current transformation matrix (CTM), which maps
  user space coordinates used within a PDF content stream into output device
  coordinates. It also includes the current color, the current clipping path, and
  many other parameters that are implicit operands of the painting operators.
• Path construction operators specify paths, which define shapes, line trajectories,
  and regions of various sorts. They include operators for beginning a new path,
  adding line segments and curves to it, and closing it.
• Path-painting operators fill a path with a color, paint a stroke along it, or use it
  as a clipping boundary.
• Other painting operators paint certain self-describing graphics objects. These
  include sampled images, geometrically defined shadings, and entire content
  streams that in turn contain sequences of graphics operators.
• Text operators select and show character glyphs from fonts (descriptions of type-
  faces for representing text characters). Because PDF treats glyphs as general
  graphical shapes, many of the text operators could be grouped with the graph-
  ics state or painting operators. However, the data structures and mechanisms
  for dealing with glyph and font descriptions are sufficiently specialized that
  Chapter 5 focuses on them.




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