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1.4.1 The RGB Color Model

The red-green-blue model is formed by a color cube $ \{(R,G,B):0\leq R,G,B\leq 1\}$.

Figure: The RGB-cube
\begin{figure}\begin{picture}(5,5)(-1,-1) \put(0,0){\makebox(0,0){$\bullet$}\lin... ...kebox(0,0){Black}} \put(1.5,2.2){\makebox(0,0){White}} \end{picture}\end{figure}

Conversion from $ (R,G,B)$ to $ (X,Y,Z)$ is given via the chromaticities $ (X_r,Y_r,Z_r)$, $ (X_g,Y_g,Z_g)$ and $ (X_b,Y_b,Z_b)$ of the CRTs phosphors by matrix multiplication via:

$\displaystyle \begin{pmatrix} X \\ Y \\ Z \end{pmatrix}= \begin{pmatrix} Xr & X... ...Zr & Z_g & Z_b \\ \end{pmatrix}\cdot \begin{pmatrix} R \\ G \\ B \end{pmatrix}$

Let $ C_r:=X_r+Y_r+Z_r$. Then $ X_r=x_r\cdot C_r$, $ Y_r=y_r\cdot C_r$ and $ Z_r=z_r\cdot C_r=(1-x_r-y_r)\cdot C_r$.

This can be calculated from $ X=\frac{x}{y}Y$, $ Y=Y$, $ Z=\frac{1-x-y}{y}Y$.

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Next: 1.4.2 The CMY Color Up: 1.4 Color models for Previous: 1.4 Color models for
Andreas Kriegl 2003-07-23