Apparatus and methods for encoding, decoding and representing high dynamic range images
First Claim
1. A method for encoding a high dynamic range (HDR) image, the method comprising:
- generating a lower dynamic range (LDR) image by tone mapping the HDR image, the LDR image having a lower dynamic range than the HDR image;
computing an original ratio image, wherein each pixel value of the original ratio image comprises a ratio of a luminance of a pixel of the HDR image and a luminance of a corresponding pixel of the LDR image; and
computing a transformed ratio image by applying a non-linear invertible function to the original ratio image;
generating a compressed transformed ratio image by compressing the transformed ratio image; and
generating a compressed file that includes both the LDR image and the compressed transformed ratio 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.
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Citations
22 Claims
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1. A method for encoding a high dynamic range (HDR) image, the method comprising:
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generating a lower dynamic range (LDR) image by tone mapping the HDR image, the LDR image having a lower dynamic range than the HDR image; computing an original ratio image, wherein each pixel value of the original ratio image comprises a ratio of a luminance of a pixel of the HDR image and a luminance of a corresponding pixel of the LDR image; and computing a transformed ratio image by applying a non-linear invertible function to the original ratio image; generating a compressed transformed ratio image by compressing the transformed ratio image; and generating a compressed file that includes both the LDR image and the compressed transformed ratio image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 18, 19)
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10. A method for decoding a high dynamic range (HDR) image, the method comprising:
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receiving a compressed file, the compressed file including a lower dynamic range (LDR) image, wherein the LDR image has a lower dynamic range than a HDR image; receiving a compressed transformed ratio image; generating a transformed ratio image by decompressing the compressed transformed ratio image; applying an inverse function of a non-linear invertible 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; and reconstructing a reconstructed HDR image, the reconstructed HDR image determined by the LDR image and the decoded ratio image. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 20, 21, 22)
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Specification