YCgCo color model
The YCgCo color model (also YCoCg ) describes the color space which is formed by the luminance Y, chrominance green Cg and chrominance orange Co. It is used, for example, in the video compression methods H.264 / MPEG-4 AVC and Dirac , as it leads to a stronger decorrelation of the color planes compared to other color models .
Comparison with other color models
RGB color model
The three values of the YCgCo color model can be calculated from the three color values of the RGB color model as follows:
The values of the luminance Y are in the range from 0 to 1, chrominance green Cg and chrominance orange Co in the range from −0.5 to 0.5. A pure red corresponds, for example, in the RGB system (1,0,0) and in the YCgCo system (1/4, -1 / 4.1 / 2).
The conversion from the YCgCo color model to the RGB color model results from the inverted matrix to:
In order to realize this conversion, only 2 additions and 2 subtractions are necessary. Furthermore, no real coefficients are necessary, which means that the transformation can be implemented efficiently as integer additions and subtractions:
tmp := Y − Cg;
R := tmp + Co;
G := Y + Cg;
B := tmp − Co;
YCbCr color model
Compared to the YCbCr color model, the YCgCo color model has the advantage of a simpler and faster calculation as well as a stronger decorrelation of the color planes.
literature
- Tilo Strutz: Image data compression. Basics, coding, wavelets, JPEG, MPEG, H.264 4th edition, Vieweg + Teubner 2009, ISBN 978-3-8348-0472-3 (print), ISBN 978-3-8348-9986-6 (online)
Research on the YCgCo color model:
- H. Malvar, G. Sullivan: YCoCg-R: A color space with RGB reversibility and low dynamic range. ISO / IEC JTC1 / SC29 / WG11 and ITU-T SG16 Q.6, Document JVT-I014, 2003.
- S. Sun: Residual Color Transform Using YCoCg-R. ISO / IEC JTC1 / SC29 / WG11 and ITU-T Q6 / SG16, Document JVT-L014, March 2004.
- Woo-Shik Kim, Dmitry Birinov, Dae-Sung Cho, Hyun Mun Kim (Multimedia Lab, Samsung AIT); Video Coding Experts Group (VCEG): Enhancements to RGB coding in H.264 / MPEG-4 AVC FRExt . Proposal, 26th Meeting: Busan, KR, 16–22. April 2005, ITU Document VCEG-Z16 ( MS Word )
- P. Agawane, KR Rao (Multimedia Processing Lab, University of Arlington): Implementation and evaluation of residual color transform for 4: 4: 4 lossless RGB coding. International Conference on Recent Advances in Communication Engineering, Hyderabad, India. December 20-23, 2008, uta.edu ( ppt )
Individual evidence
- ^ Dirac Specification. (PDF; 891 kB) (No longer available online.) P. 136 , archived from the original on May 3, 2015 ; accessed on May 4, 2010 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b YCoCg: A Color Space with RGB Reversibility. ( ppt ; 583 kB) University of Texas at Arlington, accessed on May 2, 2010 (English).
- ↑ a b Yair Moshe: H.264 Amendment: Fidelity Range Extensions. (PDF) (No longer available online.) Signal and Image processing Lab (SIPL), p. 15 , archived from the original on October 6, 2014 ; accessed on May 2, 2010 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.