Method and apparatus for processing image data
AssigneeInterDigital VC Holdings, Inc.
InventorsPatrick Lopez, Fabrice Leleannec, Yannick Olivier, David Touze
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Abstract
The invention concerns scaling color difference components prior to encoding in order to extend the dynamic range. In one embodiment the color difference components are encoded prior to quantization. In another embodiment the color difference components are encoded after quantization. A decoder is configured to process data representative of the gain factor for a decoding process.
Claims28
A method of encoding image data including first, second and third color components defining color characteristics of image portions in a color space, the method comprising for at least a portion of an image:
- scaling a first color difference component and a second color difference component obtained from the first, second and third color components of the image portion, by applying a gain factor to extend a respective dynamic range of the first color difference component and the second color difference component, the first color difference component being defined as a weighted difference between the third color component and the first color component and the second color difference component being defined as a weighted difference between the second color component and the first color component, wherein the gain factor applied to a color difference component is dependent upon the color gamut of the color space;
- and
- encoding the scaled first and second color difference components.
A method for decoding image data including first, second and third color components defining color characteristics of image portions in a color space, the method comprising for at least a portion of an image:
- decoding a received data bitstream;
- obtaining, from the decoded bitstream, a first color difference component and a second color difference component;
- rescaling the first color difference component and the second color difference component by applying a rescaling factor corresponding to a gain factor applied to the first and second color difference components prior to encoding, wherein the gain factor is dependent upon the color gamut of the color space, the first color difference component being defined as a weighted difference between the third color component and the first color component and the second color difference component being defined as a weighted difference between the second color component and the first color component;
- and
- processing the rescaled first and second color difference components to obtain corresponding color components of the image portion.
An encoder for encoding image data including first, second and third color components defining color characteristics of image portions in a color space, the encoder comprising a processor configured for:
- scaling a first color difference component and a second color difference component, obtained from the first, second and third color components of an image portion, by applying a gain factor to extend their a respective dynamic range of the first color difference component and the second color difference component, the first color difference component being defined as a weighted difference between the third color component and the first color component and the second color difference component being defined as a weighted difference between the second color component and the first color component, wherein the gain factor applied to a color difference component is dependent upon the color gamut of the color space;
- and
- encoding the scaled first and second color difference components.
A decoder for decoding image data including first, second and third color components defining color characteristics of image portions in a color space, the decoder comprising a processor configured for:
- decoding a received bitstream;
- obtaining, from the decoded bitstream, a first color difference component and a second color difference component;
- rescaling the first color difference component and the second color difference component by applying a rescaling factor corresponding to a gain factor applied to the first and second color difference components prior to encoding, wherein the gain factor is dependent upon the color gamut of the color space, the first color difference component being defined as a weighted difference between the third color component and the first color component and the second color difference component being defined as a weighted difference between the second color component and the first color component;
- and
- processing the rescaled first and second color difference components to obtain corresponding color components of an image portion.
A non-transitory computer-readable medium including instructions for causing one or more processors to perform encoding image data including first, second and third color components defining color characteristics of image portions in a color space, the encoding comprising for at least a portion of an image:
- scaling a first color difference component and a second color difference component obtained from the first, second and third color components of the image portion, by applying a gain factor to extend a respective dynamic range of the first color difference component and the second color difference component, the first color difference component being defined as a weighted difference between the third color component and the first color component and the second color difference component being defined as a weighted difference between the second color component and the first color component, wherein the gain factor applied to a color difference component is dependent upon the color gamut of the color space;
- and
- encoding the scaled first and second color difference components.
Dependencies are inferred from the claim text.