Effective Compression of High Dynamic Range Images

There's a plenty of file formats designed for storing high dynamic range (HDR) images. But none of them provide satisfactory compression ratio and backward compatibility with existing file formats. In this paper we propose an approach to lossy compressing HDR data in a standard JPEG/JFIF file. An original HDR file is decomposed into a tone mapped version of it LDR (low dynamic range) 24bpp and additional information needed to restore the original HDR image from LDR. The LDR image is compressed using standard JPEG encoder and forms a foreground image. Extra data is carried wavelet-compressed as a subband in the file. Naive (not HDR-enabled) applications will see the image as a normal JPEG/JFIF file and will extract only the LDR data giving user a preview of the original HDR image. HDR-enabled applications will extract additional information from the subband channel and restore the HDR image. The results of compressing a series of natural and synthetic HDR images using various tone mapping operators and lossy compression settings are presented and discussed in the paper.