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ICTCP, 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[1]. I is the intensity luma component encoded using the PQ SMPTE ST 2084[2] or Hybrid Log-Gamma non-linearity and CT and CP are the blue-yellow (named from tritanopia) and red-green (named from protanopia) chroma components[3].


ICtCp is defined from BT.2100 RGB[1] as follows:


Calculate LMS from BT.2100:


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


Calculate ICtCp:


ICTCP is near constant luminance, which improves chroma subsampling versus YCbCr[4]. ICTCP also improves hue linearity compared with YCbCr which helps with compression performance and color volume mapping [5]. With reshaping, ICTCP can improve compression performance by 10%[6].

References

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  1. ^ a b "BT.2100-0 : Image parameter values for high dynamic range television for use in production and international programme exchange". International Telecommunication Union.
  2. ^ "ST 2084:2014". Society of Motion Picture and Television Engineers.
  3. ^ "ICtCp White Paper" (PDF). Dolby Laboratories, Inc.
  4. ^ "Subsampling in ICtCp vs YCbCr" (PDF). Dolby Laboratories, Inc.
  5. ^ "ITP Colour Space and Its Compression Performance for High Dynamic Range and Wide Colour Gamut Video Distribution" (PDF). ZTE.
  6. ^ "Evaluation of ICtCp color space and an Adaptive Reshaper for HDR and WCG". IEEE url=https://infoscience.epfl.ch/record/222897/files/IEEEpaper.pdf. {{cite web}}: Missing or empty |url= (help); Missing pipe in: |publisher= (help)