[pstricks] Real transparency hack

[MLuque5130 at aol.com]

The problem of the transparency seems to arouse some interest and if 
according to the message of Jan Steffan, the problem seems to be solved in the new 
versions of GhostScript, it is a good news.
However, if you want to arrange it by yourself, it is possible.
This problem can be dealt with by the use of coding CMYK. When two surfaces 
of different colors are superimposed, the resulting color has as components the 
addition of the respective colors as in the example below.
It is the result of the superposition, on an overhead projector, of three 
transparencies.
Each transparency contains only diagram.
Is it possible to build something of more general?  I subject this problem to 
you...

%%%%%%%%%%%%%%%%%%%%%%%%%
% 14 juillet 2005
\documentclass{article}
\usepackage{pstricks}
\SpecialCoor
\newcommand{\CyanA}{0.5}
\newcommand{\MagentaA}{0}
\newcommand{\YellowA}{0.1}
\newcommand{\CyanB}{0.05}
\newcommand{\MagentaB}{0.4}
\newcommand{\YellowB}{0.1}
\newcommand{\CyanC}{0.2}
\newcommand{\MagentaC}{0.1}
\newcommand{\YellowC}{0.5}
\newcommand{\VeenA}{%
    \psccurve(4;30)(4.2;90)(4.1;150)(4.2;210)(3.9;270)(4.2;330)}
\newcommand{\VeenB}{%
    \psccurve(4.5;30)(4.3;90)(4.1;150)(4;210)(4.2;270)(4;330)}
\newcommand{\VeenC}{%
    \psccurve(4;30)(4.1;90)(4.2;150)(4.3;210)(4.2;270)(4.1;330)}
% Denis Girou
\makeatletter
\newcommand{\NewColorCMYK}[2]{\@newcolor{#1}{#2 setcmykcolor}}
\makeatother
%
\newcommand{\VeenDiagramTransparency}{%
\NewColorCMYK{A}{\CyanA\space \MagentaA\space \YellowA\space 0}
\NewColorCMYK{B}{\CyanB\space \MagentaB\space \YellowB\space 0}
\NewColorCMYK{C}{\CyanC\space \MagentaC\space \YellowC\space 0}
\NewColorCMYK{AB}{\CyanA\space \CyanB\space add
                  \MagentaA\space \MagentaB\space add
                  \YellowA\space \YellowB\space add 0}
\NewColorCMYK{BC}{\CyanB\space \CyanC\space add
                  \MagentaB\space \MagentaC\space add
                  \YellowB\space \YellowC\space add 0}
\NewColorCMYK{AC}{\CyanA\space \CyanC\space add
                  \MagentaA\space \MagentaC\space add
                  \YellowA\space \YellowC\space add 0}
\NewColorCMYK{ABC}{\CyanA\space \CyanB\space add \CyanC\space add
                   \MagentaA\space \MagentaB\space add \MagentaC\space add
                   \YellowA\space \YellowB\space add \YellowC\space add 0}
\rput(1,-1){\psset{fillstyle=solid,fillcolor=B}\VeenB}
\rput(-2,0){\psset{fillstyle=solid,fillcolor=A}\VeenA}
\rput(2,2){\psset{fillstyle=solid,fillcolor=C}\VeenC}
% A inter B
\psclip{\rput(-2,0){\VeenA}}
\rput(1,-1){\psset{fillstyle=solid,fillcolor=AB}\VeenB}
\endpsclip%
% B inter C
\psclip{\rput(1,-1){\VeenB}}
\rput(2,2){\psset{fillstyle=solid,fillcolor=BC}\VeenC}
\endpsclip%
% A inter C
\psclip{%
\rput(-2,0){\VeenA}}
\rput(2,2){\psset{fillstyle=solid,fillcolor=AC}\VeenC}
\endpsclip%
% A inter B inter C
\psclip{\rput(-2,0){\VeenA}}
    \psclip{\rput(1,-1){\VeenB}}
        \rput(2,2){\psset{fillstyle=solid,fillcolor=ABC}\VeenC}
\endpsclip%
\endpsclip%
\rput(1,-1){\VeenB}
\rput(-2,0){\VeenA}
\rput(2,2){\VeenC}}
\begin{document}
\begin{center}
\begin{pspicture}(-4,-5)(4,4)
\VeenDiagramTransparency
\end{pspicture}
\renewcommand{\CyanA}{0.3}
\renewcommand{\MagentaA}{0.2}
\renewcommand{\YellowA}{0.1}
\renewcommand{\CyanB}{0.1}
\renewcommand{\MagentaB}{0.3}
\renewcommand{\YellowB}{0.3}
\renewcommand{\CyanC}{0.1}
\renewcommand{\MagentaC}{0}
\renewcommand{\YellowC}{0.6}
\renewcommand{\VeenA}{%
    \psccurve(4;30)(4.2;90)(4.3;150)(3.9;210)(4.1;270)(3.7;330)}
\renewcommand{\VeenB}{%
    \psccurve(4.2;30)(3.9;90)(4;150)(4.1;210)(4.2;270)(4;330)}
\renewcommand{\VeenC}{%
    \psccurve(4.1;30)(3.8;90)(4.2;150)(3.9;210)(3.7;270)(4.1;330)}
\begin{pspicture}(-4,-4)(4,6)
\VeenDiagramTransparency
\end{pspicture}
\end{center}
\end{document}


Manuel Luque
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