Improved reversible integer-to-integer color transforms

The integer color transform is a reversible operation that can transform one color coordinate into another one and both the inputs and the outputs are of integer forms. In this paper, we improve the integer color transforms derived in previous works. First, we relax the constraint that the scaling for each row should be the same. From this, the method of deriving the integer color transform becomes more flexible and we can derive the integer color transform with less implementation time and higher accuracy. Moreover, we use the new criterion, bit extension, to measure the performance of the integer color transform and propose a new way for accuracy analysis. With the proposed method, we derive the reversible integer RGB-to-YCbCr, KLA, XYZ, UVW, RcGcBc, and YUV transforms with even higher accuracy successfully.