Lossless integer color transform for four color components

This report proposes an integer color transform for lossless coding of four color components of images. An existing color transform has a fixed set of coefficients and therefore it can't be adaptive to each image. We utilize eigen-vector of the covariance of the four components to increase data compaction performance. We also utilize fixed relation between two green components to simplify computational cost of the transform. It was confirmed that the proposed method reduces entropy rate by 0.4 bit comparing to the existing method.