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
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}.
26
c.fill(path.rect(0, 0, 7, 3), [color.gray(0.8)])
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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])
31
c.writeEPSfile("color")
35
The file \verb|color.eps| is created and looks like:
37
\includegraphics{color}
40
\section{Color gradients}
42
The color module provides a class \verb|gradient| for continous transitions between
43
colors. A list of named gradients is available in appendix~\ref{gradientname}.
45
\begin{classdesc}{gradient}{min=0, max=1}
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This class provides the methods for the \verb|gradient|. Different
47
initializations can be found in \verb|lineargradient| and
48
\verb|functiongradient|.
50
\var{min} and \var{max} provide the valid range of the arguments for
53
\begin{funcdesc}{getcolor}{parameter}
54
Returns the color that corresponds to \var{parameter} (must be between
55
\var{min} and \var{max}).
58
\begin{funcdesc}{select}{index, n\_indices}
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When a total number of \var{n\_indices} different colors is needed from the
60
gradient, this method returns the \var{index}-th color.
66
\begin{classdesc}{lineargradient}{startcolor, endcolor, min=0, max=1}
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This class provides a linear transition between two given colors. The linear
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interpolation is performed on the color components of the specific color
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\var{startcolor} and \var{endcolor} must be colors of the same color model.
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\begin{classdesc}{functiongradient}{functions, type, min=0, max=1}
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This class provides an arbitray transition between colors of the same
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\var{type} is a string indicating the color model (one of \code{"cmyk"},
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\code{"rgb"}, \code{"hsb"}, \code{"grey"})
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\var{functions} is a dictionary that maps the color components onto given
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functions. E.g. for \code{type="rgb"} this dictionary must have the keys
83
\code{"r"}, \code{"g"}, and \code{"b"}.
87
\section{Transparency}
89
\begin{classdesc}{transparency}{value}
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Instances of this class will make drawing operations (stroking,
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filling) to become partially transparent. \var{value} defines the
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transparency factor in the range \code{0} (opaque) to \code{1}
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Transparency is available in PDF output only since it is not
96
supported by PostScript. However, for certain ghostscript devices
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(for example the pdf backend as used by ps2pdf) proprietary
98
PostScript extension allows for transparency in PostScript code too.
99
\PyX{} creates such PostScript proprietary code, but issues a
100
warning when doing so.