Rectangles of color, depth, and certain other values may be converted to fragments using the DrawPixels command. Some of the parameters and operations governing the operation of DrawPixels are shared by ReadPixels (used to obtain pixel values from the framebuffer) and CopyPixels (used to copy pixels from one framebuffer location to another); the discussion of ReadPixels and CopyPixels , however, is deferred until Chapter 4 after the framebuffer has been discussed in detail. Nevertheless, we note in this section when parameters and state pertaining to DrawPixels also pertain to ReadPixels or CopyPixels .
A number of parameters control the encoding of pixels in client memory (for reading and writing) and how pixels are processed before being placed in or after being read from the framebuffer (for reading, writing, and copying). These parameters are set with three commands: PixelStore , PixelTransfer , and PixelMap .