Chroma Reshaping for High Dynamic Range Images

A method for adaptive chroma reshaping of a high dynamic range (HDR) image with a processor, the method comprising:

• accessing with the processor an HDR input image comprising pixel values in a luma component and one or more chroma components;
• for a chroma component of the input image:
• partitioning the pixel values of either the luma component of the HDR input image or a reshaped luma component of the HDR input image into two or more bins;
• generating for each bin a maximal scale factor based on the chroma pixel values corresponding to the respective luma or reshaped luma pixel values in each bin;
• generating a forward reshaping function based on a reference reshaping function and the maximal scale factors, the forward reshaping function mapping either luma pixel values or reshaped luma pixel values to forward chroma scale factors and correspondingly the reference reshaping function mapping luma pixel values or reshaped luma pixel values to reference chroma scale factors;
• and
• generating reshaped chroma pixel values for the chroma component based on the chroma pixel values, the forward reshaping function, and the corresponding luma pixel values or reshaped luma pixel values of the HDR input image.