YDbDr, sometimes written <math>YD_BD_R</math>, is the colour space<ref>Template:Cite book</ref> used in the SECAM (adopted in France and some countries of the former Eastern Bloc) analog colour television broadcasting standard.<ref name=":0">Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref> It is very close to YUV (used on the PAL system) and its related colour spaces such as YIQ (used on the NTSC system), YPbPr and YCbCr.<ref>Template:Cite book</ref><ref>Template:Cite book</ref>
<math>YD_BD_R</math> is composed of three components: <math>Y</math>, <math>D_B</math> and <math>D_R</math>. <math>Y</math> is the luminance, <math>D_B</math> and <math>D_R</math> are the chrominance components, representing the red and blue colour differences.<ref>Template:Cite book</ref>
FormulasEdit
The three component signals are created from an original <math>RGB</math> (red, green and blue) source. The weighted values of <math>R</math>, <math>G</math> and <math>B</math> are added together to produce a single <math>Y</math> signal, representing the overall brightness, or luminance, of that spot. The <math>D_B</math> signal is then created by subtracting the <math>Y</math> from the blue signal of the original <math>RGB</math>, and then scaling; and <math>D_R</math> by subtracting the <math>Y</math> from the red, and then scaling by a different factor.
These formulae approximate the conversion between the RGB colour space and <math>YD_BD_R</math>.
- <math>\begin{align}
R, G, B, Y &\in \left[ 0, 1 \right]\\ D_B, D_R &\in \left[ -1.333, 1.333 \right]\end{align}</math>
From RGB to YDbDr:
- <math>\begin{align}
Y &= +0.299 R +0.587 G +0.114 B\\ D_B &= -0.450 R -0.883 G +1.333 B\\ D_R &= -1.333 R +1.116 G +0.217B\\ \begin{bmatrix} Y \\ D_B \\ D_R \end{bmatrix} &= \begin{bmatrix} 0.299 & 0.587 & 0.114 \\ -0.450 & -0.883 & 1.333 \\ -1.333 & 1.116 & 0.217 \end{bmatrix} \begin{bmatrix} R \\ G \\ B \end{bmatrix}\end{align}</math>
From YDbDr to RGB:
- <math>\begin{align}
R &= Y +0.000092303716148 D_B -0.525912630661865 D_R\\ G &= Y -0.129132898890509 D_B +0.267899328207599 D_R\\ B &= Y +0.664679059978955 D_B -0.000079202543533 D_R\\ \begin{bmatrix} R \\ G \\ B \end{bmatrix} &= \begin{bmatrix} 1 & 0.000092303716148 & -0.525912630661865 \\ 1 & -0.129132898890509 & 0.267899328207599 \\ 1 & 0.664679059978955 & -0.000079202543533 \end{bmatrix} \begin{bmatrix} Y \\ D_B \\ D_R \end{bmatrix}\end{align}</math>
You may note that the <math>Y</math> component of <math>YD_BD_R</math> is the same as the <math>Y</math> component of <math>Y</math><math>U</math><math>V</math>. <math>D_B</math> and <math>D_R</math> are related to the <math>U</math> and <math>V</math> components of the YUV colour space as follows:
- <math>\begin{align}
D_B &= + 3.059 U\\ D_R &= - 2.169 V\end{align}</math>
See alsoEdit
- YUV - related colour system
ReferencesEdit
- Shi, Yun Q. and Sun, Huifang Image and Video Compression for Multimedia Engineering, CRC Press, 2000 Template:ISBN