One of the strengths of OpenGL is that it provides tools for both image processing and 3D rendering. Unlike some libraries that contain only one or the other, OpenGL was designed with the understanding that many image processing tools are useful for 3D graphics. For example, convolution may be used to implement depth-of-field effects. Conversely, many operations typically thought of as image processing operations may be cast as geometric rendering and texture mapping operations. Electronic light tables (ELT's) used for defense imaging require image transformations which can be implemented using OpenGL's textured drawing capabilities. In this section, we will explore image processing applications of OpenGL, beginning with color manipulation, moving on to convolution, and finally discussing image warping. To solve these problems, we have three major parts of OpenGL at our disposal: the pixel transfer pipeline, geometric drawing and texturing, and fragment operations.