ICtCp

ICTCP, ICtCp, or ITP is a color representation format specified in the Rec. ITU-R BT.2100 standard that is used as a part of the color image pipeline in video and digital photography systems for high dynamic range (HDR) and wide color gamut (WCG) imagery.[1] It was developed by Dolby Laboratories[2] from the IPT color space by Ebner and Fairchild.[3][4] The format is derived from an associated RGB color space by a coordinate transformation that includes two matrix transformations and an intermediate nonlinear transfer function that is informally known as gamma pre-correction. The transformation produces three signals called I, CT, and CP. The ICTCP transformation can be used with RGB signals derived from either the perceptual quantizer (PQ) or hybrid log–gamma (HLG) nonlinearity functions, but is most commonly associated with the PQ function (which was also developed by Dolby).

The I ("intensity") component is a luma component that represents the brightness of the video, and CT and CP are blue-yellow (named from tritanopia) and red-green (named from protanopia) chroma components.[2] Ebner also used IPT as short for "Image Processing Transform".[3]

The ICTCP color representation scheme is conceptually related to the LMS color space, as the color transformation from RGB to ICTCP is defined by first converting RGB to LMS with a 3×3 matrix transformation, then applying the nonlinearity function, and then converting the nonlinear signals to ICTCP using another 3×3 matrix transformation.[5] ICTCP was defined as a YCC digital format with support for 4:4:4, 4:2:2 and 4:2:0 chroma subsampling in CTA-861-H (that means that in limited range 10 bit mode 0, 1, 2, 3, 1020, 1021, 1022, 1023 values are reserved).[6]

  1. ^ "BT.2100-2: Image parameter values for high dynamic range television for use in production and international programme exchange". ITU-R. July 2018.
  2. ^ a b "What Is ICtCp – Introduction?" (PDF). Dolby. Retrieved 2016-04-20.
  3. ^ a b Ebner, Fritz (1998-07-01). "Derivation and modelling hue uniformity and development of the IPT color space". Theses.
  4. ^ F.Ebner, M.D.Fairchild, Development and testing of a color space (IPT) with improved hue uniformity. In: Proceedings of The Sixth Color Imaging Conference, 8-13, 1998
  5. ^ "ST 2084:2014". Society of Motion Picture and Television Engineers.
  6. ^ "A DTV Profile for Uncompressed High Speed Digital Interfaces (ANSI/CTA-861-H)". Consumer Technology Association®. Retrieved 2021-03-11.