Signal reshaping and coding in the IPT-PQ color space

In a decoder, a method to reconstruct an input image coded in a reshaped perceptually-quantized IPT (IPT-PQ) color space, the method comprising:

• accessing metadata characterizing the color transformation of the input image in an encoder from a first color space to the reshaped IPT-PQ color space;
• and
• transforming by a processor the input image from the reshaped IPT-PQ color space to an output image in an output color space, wherein the transforming step comprises one or more of the following steps:
• swapping the chroma components of the input image;
• reversing the sign of pixel values of the T color component of the input image;
• multiplying pixel values of the chroma components of the input image by a factor of two;
• applying an IPT to non-linear LMS color transformation matrix to the input image, wherein the color transformation may incorporate one or more of the chroma swapping, the chroma sign reversing, or the chroma multiplying by a factor of two.