Interpolation of reshaping functions
AssigneeDolby Laboratories Licensing Corporation
InventorsHarshad Kadu, Qing Song, Guan-Ming Su
Life of this patent
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Abstract
Methods and systems for generating an interpolated reshaping function for the efficient coding of high-dynamic range images are provided. The interpolated reshaping function is constructed based on a set of pre-computed basis reshaping functions. Interpolation schemes are derived for pre-computed basis reshaping functions represented as look-up tables, multi-segment polynomials, or matrices of coefficients in a multivariate, multi-regression representation. Encoders and decoders using asymmetric reshaping and interpolated reshaping functions for mobile applications are also presented.
Claims19
A method for generating in a computer apparatus a reshaping function for reshaping an input image in a first codewords representation to a reshaped image in a second codewords representation, the method comprising:
- accessing a first set of pre-computed reshaping functions, wherein a pre-computed reshaping function of the first set maps pixel codewords from the first codeword representation to the second codeword representation and each reshaping function is identified by a value of a parameter, wherein the value of the parameter corresponds to a device setting of a device for capturing or displaying the input image or the reshaped image;
- receiving an input image in the first codeword representation and a parameter identifying the reshaping function to be generated, wherein the first set of pre-computed reshaping functions does not comprise the reshaping function to be generated;
- identifying within the first set of pre-computed reshaping functions a first pre-computed reshaping function identified by a first parameter having a first value lower than a value of the received parameter and a second pre-computed reshaping function identified by a second parameter having a second value higher than the value of the received parameter, the value of the received parameter being different from any values of the parameters identifying the pre-computed reshaping functions of the first set;
- generating the reshaping function by interpolating the first pre-computed reshaping function and the second pre-computed reshaping function based on an interpolation factor computed using the received parameter, the first parameter, and the second parameter;
- applying the generated reshaping function to the input image to generate the reshaped image in the second codeword representation;
- and
- coding the reshaped image to generate a coded reshaped image.
A method to decode a coded image, the method comprising:
- receiving a coded reshaped image in a first codeword representation and a received parameter;
- decoding the coded reshaped image to generate a first decoded image in the first codeword representation;
- accessing a set of pre-computed reshaping functions, wherein a reshaping function maps pixel codewords from the first codeword representation to a second codeword representation and each reshaping function is identified by a value of a parameter identifying the reshaping function, wherein the value of the parameter comprises a device setting of a device for capturing or displaying the input image or the reshaped image;
- identifying within the set of pre-computed reshaping functions a first pre-computed reshaping function identified by a first parameter having a first value lower than a value of the received parameter and a second pre-computed reshaping function identified by a second parameter having a second value higher than the value of the received parameter, the value of the received parameter being different from any values of the parameters identifying the pre-computed reshaping functions of the first set;
- generating an output reshaping function by interpolating the first pre-computed reshaping function and the second pre-computed reshaping function using the received parameter, wherein the accessed set of pre-computed reshaping functions does not comprise the output reshaping function;
- and
- applying the output reshaping function to the first decoded image to generate an output image in the second codeword representation.
Dependencies are inferred from the claim text.