On performance of lossless compression for HDR image quantized in color space

High dynamic range (HDR) image requires a higher number of bits per color channel than traditional images. This brings about problems to storage and transmission. Color space quantization has been extensively studied to achieve bit encodings for each pixel and still yields prohibitively large files. This paper explores the possibility of further compressing HDR images quantized in color space. The compression schemes presented in this paper extends existing lossless image compression standards to encode HDR images. They separate HDR images in their bit encoding formats into images in grayscale or RGB domain, which can be directly compressed by existing lossless compression standards such as JPEG, JPEG 2000 and JPEG-LS. The efficacy of the compression schemes is illustrated by presenting extensive results of encoding a series of synthetic and natural HDR images. Significant bit savings of up to 53% are observed when comparing with original HDR formats and HD Photo compressed version. This is beneficial to the storage and transmission of HDR images.