One useful tool for color modification is the look-up table. Generally speaking, a look-up table maps an input value to a location in a table, and replaces that value with the table entry. Two look-up tables in OpenGL, pixel maps and color tables, map components independently in one-dimensional tables. These mechanisms provide efficient mapping for applications requiring no correspondence between the channels of the image. A third mechanism, pixel texturing, uses the OpenGL texturing capability to perform multi-dimensional look-ups.