manual/color.tex

   1 \chapter{Module color}
   2 \label{color}
   3 \section{Color models}
   4 PostScript provides different color models. They are available to
   5 \PyX{} by different color classes, which just pass the colors down to
   6 the PostScript level. This implies, that there are no conversion
   7 routines between different color models available. However, some color
   8 model conversion routines are included in Python's standard library in
   9 the module \texttt{colorsym}. Furthermore also the comparison of
  10 colors within a color model is not supported, but might be added in
  11 future versions at least for checking color identity and for ordering
  12 gray colors.
  13
  14 There is a class for each of the supported color models, namely
  15 \verb|gray|, \verb|rgb|, \verb|cmyk|, and \verb|hsb|. The constructors
  16 take variables appropriate for the color model. Additionally, a list of
  17 named colors is given in appendix~\ref{colorname}.
  18
  19 \section{Example}
  20 \begin{quote}
  21 \begin{verbatim}
  22 from pyx import *
  23
  24 c = canvas.canvas()
  25
  26 c.fill(path.rect(0, 0, 7, 3), [color.gray(0.8)])
  27 c.fill(path.rect(1, 1, 1, 1), [color.rgb.red])
  28 c.fill(path.rect(3, 1, 1, 1), [color.rgb.green])
  29 c.fill(path.rect(5, 1, 1, 1), [color.rgb.blue])
  30
  31 c.writeEPSfile("color")
  32 \end{verbatim}
  33 \end{quote}
  34
  35 The file \verb|color.eps| is created and looks like:
  36 \begin{quote}
  37 \includegraphics{color}
  38 \end{quote}
  39
  40 \section{Color palettes}
  41
  42 The color module provides a class \verb|palette|. The constructor of
  43 that class receives two colors from the same color model and two
  44 named parameters \verb|min| and \verb|max|, which are set to \verb|0|
  45 and \verb|1| by default. Between those colors a linear interpolation
  46 takes place by the method \verb|getcolor| depending on a value between
  47 \verb|min| and \verb|max|.
  48
  49 A list of named palettes is available in appendix~\ref{palettename}.
  50