Reversible integer color transform with bit-constraint

In color image processing, the RGB color coordinate is usually transformed into another one (e.g., YIQ or KLA) for system fitting or other purposes. Most of the color transforms are done by 3×3 matrices. However, these matrices are always not fixed-point. In this paper, we use a systematic algorithm to convert every 3×3 color transform into a reversible integer-to-integer transform. The resulted transform can be implemented with only fixed-point processor and no floating-point processor is required. Moreover, with the use of ladder-truncation technique, we can make least bit of the output the same as that of the input, and the long bit-length problem that always occurs for other integer transforms can be avoided. We derive the integer color transforms of RGB-to-KLA, IV₁V₂, YCrCb, DCT, and YIQ successfully.