Apparatus and methods for encoding, decoding and representing high dynamic range images
First Claim
1. A decoding method comprising:
- receiving a JPEG compressed file, the JPEG compressed file includes a low dynamic range (LDR) image and a transformed ratio image, the transformed ratio image separated as an application extension from the LDR image;
decompressing the compressed JPEG file to retrieve the LDR image and the transformed ratio image, wherein the decompressing comprises dequantizing a quantized transformed ratio image to generate a transformed ratio image;
applying an inverse non-linear function to the transformed ratio image to generate a decoded ratio image;
reconstructing a reconstructed HDR image, the reconstructed HDR image determined by the LDR image and the decoded ratio image; and
providing the reconstructed HDR image for display,wherein the LDR image has a lower dynamic range than the reconstructed HDR image, andwherein each pixel value of the decoded ratio image is from a ratio of a luminance of a pixel of an HDR image and a luminance of a corresponding pixel of the LDR image.
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Abstract
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.
22 Citations
18 Claims
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1. A decoding method comprising:
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receiving a JPEG compressed file, the JPEG compressed file includes a low dynamic range (LDR) image and a transformed ratio image, the transformed ratio image separated as an application extension from the LDR image; decompressing the compressed JPEG file to retrieve the LDR image and the transformed ratio image, wherein the decompressing comprises dequantizing a quantized transformed ratio image to generate a transformed ratio image; applying an inverse non-linear function to the transformed ratio image to generate a decoded ratio image; reconstructing a reconstructed HDR image, the reconstructed HDR image determined by the LDR image and the decoded ratio image; and providing the reconstructed HDR image for display, wherein the LDR image has a lower dynamic range than the reconstructed HDR image, and wherein each pixel value of the decoded ratio image is from a ratio of a luminance of a pixel of an HDR image and a luminance of a corresponding pixel of the LDR image. - View Dependent Claims (2, 3, 4, 5, 6, 14, 18)
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7. A method for decoding a high dynamic range (HDR) image, the method comprising:
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receiving a compressed file, the compressed file includes a low dynamic range (LDR) image, wherein the LDR image has a lower dynamic range than the HDR image; decompressing the compressed file to retrieve the LDR image, wherein the decompressing comprises dequantizing a quantized trasformed ratio image to generate a transformed ratio image; receiving a transformed ratio image; applying an inverse non-linear function to the transformed ratio image to generate a decoded ratio image, wherein each pixel value of the decoded ratio image is a ratio of a luminance of a pixel of the HDR image and a luminance of a corresponding pixel of the LDR image; reconstructing a reconstructed HDR image, the reconstructed HDR image determined by the LDR image and the decoded ratio image, and providing the reconstructed HDR image for display. - View Dependent Claims (8, 9, 10, 11, 12, 13, 15, 16, 17)
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Specification