These were just a few of the questions that ran through my mind when I first read the book's title. The core X specification's ability to display or enhance images is limited to three uncompromising formats. By design, core X ships images uncompressed across a network. It does not support imaging industry standard formats or standard image compression algorithms. Each image must be matched to a given display type.
Image work has to be done at a very low level of abstraction.
Unfortunately for X, the real world of imaging includes many other file formats, encoding, and compression techniques. In response to these library limitations the XIELib API was created. Based on X11R6, XIE was released three years ago along with X11R6. Descriptions and release notes for each client are provided in CD readme files. By the way, the author took time to point out that the sample client code was written and compiled using GNU tools on a Linux-powered box.