Coding of high dynamic range images in JPEG XR / HD Photo

High Dynamic Range (HDR) imaging support is one of the major features for the emerging draft JPEG XR standard. JPEG XR is being standardized within the JPEG committee based on Microsoft technology known as HD Photo. JPEG XR / HD Photo is primarily an integer-based coding technology design, accepting integer valued samples at the encoder and producing integer valued samples at the decoder, with internal processing entirely in the integer space. Yet, it can support compression of multiple HDR formats, including 16- and 32-bit float, 16-bit and 32-bit signed and unsigned integer, and RGBE. Further, JPEG XR can enable lossless compression of some HDR formats such as 16-bit signed and unsigned, 16-bit float and RGBE. This paper describes how HDR formats are handled in JPEG XR. It examines in depth how these various HDR formats are converted to and from integer valued samples within the JPEG XR codec, and the internal processing of these HDR formats. This paper describes how JPEG XR provides flexible ways to compress HDR formats within the same codec framework as integer-valued formats, while maintaining from the high compression efficiency and low computational complexity.