User:Smoro100/sandbox

IC_TC_P, ICtCp, or ITP is a color space used as a part of the color image pipeline in video and digital photography systems for High-Dynamic-Range and Wide-Color-Gamut imagery and is specified in ITU-R BT.2100. I is the intensity luma component encoded using the PQ SMPTE ST 2084 or Hybrid Log-Gamma non-linearity and C_T and C_P are the blue-yellow (named from tritanopia) and red-green (named from protanopia) chroma components.

ICtCp is defined from BT.2100 RGB as follows:

Calculate LMS from BT.2100:

${\begin{aligned}L&=(1688\cdot R+2146\cdot G+262\cdot B)/4096\\M&=(683\cdot R+2951\cdot G+462\cdot B)/4096\\S&=(99\cdot R+309\cdot G+3688\cdot B)/4096\\\end{aligned}}$

Calculate L'M'S' using the PQ inverse EOTF (the HLG OETF may also be used):

${\begin{aligned}L'&=EOTF_{PQ}^{-1}(L)\\M'&=EOTF_{PQ}^{-1}(M)\\S'&=EOTF_{PQ}^{-1}(S)\\\end{aligned}}$

Calculate ICtCp:

${\begin{aligned}I&=(0.5\cdot L'+0.5\cdot M')\\C_{T}&=(6610\cdot L'-13613\cdot M'+7003\cdot S')/4096\\C_{P}&=(17933\cdot L'-17390\cdot M'-543\cdot S')/4096\\\end{aligned}}$

IC_TC_P is near constant luminance, which improves chroma subsampling versus YCbCr. IC_TC_P also improves hue linearity compared with YCbCr which helps with compression performance and color volume mapping . With reshaping, IC_TC_P can improve compression performance by 10%.