IMPLEMENTING THE GAMMA CORRECTION ALGORITHM USING THE TMS320C2XX DSP

A nonlinear effect of signal transfer exists between an electrical and an optical device. For example, the transfer function of a cathode-ray picture tube (CRT) produces an output intensity proportional to some power (usually about 2.2 and referred to as the gamma factor) of the signal voltage. The nonlinear effect distorts the color displayed by the CRT. To compensate for the nonlinear effect, a gamma correction is applied to the video signal before the CRT displays it to make the intensity output of the CRT linear.

The gamma correction is an image-processing algorithm that compensates for the nonlinear effect of signal transfer between electrical and optical devices. The image processing performed by video applications, such as CRTs, digital cameras, color printers, and scanners, includes a gamma correction for the output. Although a PC may implement image-processing algorithms for its peripheral equipment, digital signal processors (DSPs), such as the Texas Instruments (TI(TM)) TMS320C2xx ('C2xx) DSP, are essential in implementing the image-processing algorithms for stand-alone systems.

This application note describes how to implement the gamma correction algorithm included with the 'C2xx DSP software. The document includes two main parts: the basic gamma correction theory and formula, and the 'C2xx gamma correction software description. Appendixes A through D present the assembly source code.

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