OpenGL Programming Guide

Chapter 8Drawing Pixels, Bitmaps, Fonts, and Images

Images

An image is similar to a bitmap, but instead of containing only a single bit for each pixel in a rectangular region of the screen, an image can contain much more information. For example, an image can contain the complete (R, G, B, A) quadruple stored at each pixel. Images can come from several sources, such as:

• A photograph that's digitized with a scanner
  
  

• An image that was first generated on the screen by a graphics program using the graphics hardware and then read back, pixel by pixel
  
  

• A software program that generated the image in memory pixel by pixel

The images you normally think of as pictures come from the color buffers. However, you can read or write rectangular regions of pixel data from or to the depth buffer or the stencil buffer. See Chapter 10 for an explanation of these other buffers.

In addition to simply being displayed on the screen, images can be used for texture maps, in which case they're essentially pasted onto polygons that are rendered on the screen in the normal way. See Chapter 9 for more information about this technique.

Reading, Writing, and Copying Pixel Data
Magnifying or Reducing an Image

OpenGL Programming Guide