Apparatus and methods for encoding, decoding and representing high dynamic range images

摘要

A data structure defining a high dynamic range image comprises a tone map having a reduced dynamic range and HDR information. The high dynamic range image can be reconstructed from the tone map and the HDR information. The data structure can be backwards compatible with legacy hardware or software viewers. The data structure may comprise a JFIF file having the tone map encoded as a JPEG image with the HDR information in an application extension or comment field of the JFIF file, or a MPEG file having the tone map encoded as a MPEG image with the HDR information in a video or audio channel of the MPEG file. Apparatus and methods for encoding or decoding the data structure may apply pre- or post correction to compensate for lossy encoding of the high dynamic range information.

主权项

1. A method for decoding a high dynamic range (HDR) image, comprising:
receiving a representation of the high dynamic range image in a compressed data structure, the representation of the high dynamic range image including a low dynamic range image and HDR image data, wherein the HDR image data include output data of a nonlinear function applied to ratios between values of a parameter as determined from the high dynamic range image and the low dynamic range image, wherein the low dynamic range image has a dynamic range that is lower than the high dynamic range image; decompressing the compressed data structure to retrieve the low dynamic range image and the HDR image data, wherein the decompressing comprises dequantizing the compressed data structure; after decompressing the compressed data structure, applying an inverse nonlinear function to the HDR image data to generate reconstructed HDR image data, wherein the reconstructed HDR image data include ratio data representing the ratios between the values of the parameter as determined from the high dynamic range image and the low dynamic range image; and after applying the inverse nonlinear function to the HDR image data to generate the reconstructed HDR image data, computing, as a multiplicative product of the low dynamic range image and corresponding ratio data of the reconstructed HDR image data, a reconstructed high dynamic range image.