Color and Images

Conclusions

We discuss the Xlib facilities for creating and using colormaps and for displaying raster images, including the XImage structure. Full-color or gray-scale images are large consumers of memory, and these usually demand their own colormaps. Displaying full pictures in color (as opposed to using a gray scale) on 8-bit displays is a challenge, but it can be done with color halftoning.

Handling colormaps with the X Window System is more complicated than with many earlier graphics systems because X tries to preserve the proper appearance for all windows in a display, so it imposes various restrictions on using colormaps. This approach is reasonable for GUIs, but it creates complications for graphics- and image-processing applications where user attention may be focused only on one or two windows. The simple design of the X server causes additional difficulties. If a display with 24 or more bits per pixel is available, displaying full pictures in color at the same time as other applications presents no problem.