Why are glDrawPixels() and glReadPixels() so slow?
While performance of the OpenGL 2D path (as its called) is acceptable on many higher-end UNIX workstation-class devices, some implementations (especially low-end inexpensive consumer-level graphics cards) never have had good 2D path performance. One can only expect that corners were cut on these devices or in the device driver to bring their cost down and decrease their time to market. When this was written (early 2000), if you purchase a graphics device for under $500, chances are the OpenGL 2D path performance will be unacceptably slow. If your graphics system should have decent performance but doesn t, there are some steps you can take to boost the performance. First, all glPixelTransfer() state should be set to their default values. Also, glPixelStore() should be set to its default value, with the exception of GL_PACK_ALIGNMENT and GL_UNPACK_ALIGNMENT (whichever is relevant), which should be set to 8. Your data pointer will need to be correspondingly double- word aligned. Second, e
