Methods to improve the quality of coding high-dynamic range (HDR) signals in the ICtCp color space are presented. Techniques are described to a) generate optimum chroma Offset and scaling parameters, b) compute chroma mode decisions by optimizing mode selection distortion metrics based on chroma saturation and hue angle values, and c) preserving iso-luminance by maintaining in-gamut values during chroma down-sampling and chroma up-sampling operations.