1. A graphical user interface for performing color correction, comprising: an interface that displays, on a background image, a user modifiable function curve that maps input values for a color component of a pixel on a first axis to output values for the color component for the pixel on a second axis, wherein pixels of the background image are the colors of output pixels having output values for the color component corresponding to an input value for the color component from an input pixel of a selected color; and means for processing modifications made to the function curve to define a color correction operation.