OpenGL provides support for handling both 3D (and 2D) geometry and 2D images. An API for use with geometry should also provide support for writing, reading, and copying images, because geometry and images are often combined, as when a 3D scene is laid over a background image. Many of the per-fragment operations that are applied to fragments arising from geometric primitives apply equally well to fragments corresponding to pixels in an image, making it easy to mix images with geometry. For example, a triangle may be blended with an image using alpha blending. OpenGL supports a number of image formats and operations on image components (such as lookup tables) to provide flexibility in image handling.