How color profile affects image and video compression efficiency

Abstract

The color values of pixels in images and videos are always stored in a specific color profile. The light intensity captured by the camera sensor is transformed to a digital color vector according to a color transfer function of the given profile. This paper presents the results of an experimental comparison of the compression efficiency with different color profiles. State-of-the-art video and image codecs are used to compress 10 and 12-bit image sequences in different color profiles. The compression ratio and visual quality are measured after decompression and comparison with the original images. The results of this study suggest that the quality/size ratio depends on the selected profile and better results can be achieved, for example, with the AgX-Log profile. AgX-Log was identified as Pareto-optimal in 79% of the measurements and was second best in quality/size ratio in the rest. Its quality/size ratio is 1.63 higher compared to the standard sRGB profile (52.10 dB PSNR at 3.12 MB vs. 48.76 dB at 5.03 MB). The optimal transfer function exhibits a high-base logarithmic curve with gradual rise toward high intensities and range cropping. These findings were validated on three external datasets.