The invention pertains to a method and apparatus for performing dynamic purity correction to insure that color purity is maintained across the face of a color monitor. The monitor displays a plurality of pixels, each having a particular luminescence value. Each luminescence value has several color components (E.g. red (R), green (G) and blue (B)). A grid of luminance measurements is made across the face of the monitor for each color component. From these luminance value grids, smoothly varying correction values are computed for each color component of each pixel by the interpolation of cubic splines, such as a Catmull-Rom spline. Incoming digital video signals are multiplied by corresponding correction values to insure color accuracy of the monitor. In a preferred embodiment, the calculation of correction values is repeatedly performed in real time (at the display dot clock rate) in a single monolithic RAMDAC integrated circuit to increase speed, improve fidelity, and minimize use of memory space.