Incorporating human visual system (HVS) models into the fractal image compression

According to the collage theorem, the encoding distortion for fractal image compression is directly related to the metric used in the encoding process. In this paper, we introduce a perceptually meaningful distortion measure based on the human visual system´s nonlinear response to luminance and the visual masking effects. Blackwell´s (1946) psychophysical raw data on contrast threshold are first interpolated as a function of background luminance and visual angle, and is then used as an error upper bound for perceptually lossless image compression. For a variety of images, experimental results show that the algorithm produces a compression ratio of 8:1 to 10:1 without introducing visual artifacts