Lossless image compression method using reversible low contrast mapping (RLCM)

This research introduces a new lossless image compression method by a transform function named a Reversible Low Contrast Mapping (RLCM). This function was successful to be implemented as a reversible watermarking method. This proposed method divides an image into fixed-size blocks and groups the blocks into watermark blocks and host blocks. Furthermore, the watermark blocks are embedded in the host blocks. The proposed method does not use any other lossless compression method in its algorithm. Nevertheless, the proposed method can still be combined with other methods. On all the testing images, the compression ratio of the proposed method achieves 1.19 on average. As a comparison, the Huffman compression ratio is 1.08. By combining the method using the Differential coding and the Golomb encoding, the compression ratio of the proposed method increases to 1.32 on average.