PostScript provides different color models. They are available to PyX by
different color classes, which just pass the colors down to the PostScript
level. This implies, that there are no conversion routines between different
color models available. However, some color model conversion routines are
included in Python’s standard library in the module
also the comparison of colors within a color model is not supported, but might
be added in future versions at least for checking color identity and for
ordering gray colors.
There is a class for each of the supported color models, namely
hsb. The constructors take variables appropriate for
the color model. Additionally, a list of named colors is given in appendix
Appendix: Named colors.
from pyx import * c = canvas.canvas() c.fill(path.rect(0, 0, 7, 3), [color.gray(0.8)]) c.fill(path.rect(1, 1, 1, 1), [color.rgb.red]) c.fill(path.rect(3, 1, 1, 1), [color.rgb.green]) c.fill(path.rect(5, 1, 1, 1), [color.rgb.blue]) c.writeEPSfile("color")
color.eps is created and looks like:
Note that all predefined non-gray gradients are defined in the RGB color space, except for gradient.Rainbow, gradient.ReverseRainbow, gradient.Hue, and gradient.ReverseHue, which are naturally defined in the HSB color space. Converted RGB and CMYK versions of these latter gradients are also defined under the names rgbgradient.Rainbow and cmykgradient.Rainbow, etc.
This class defines the methods for the
Returns the color that corresponds to parameter (must be between min and max).
When a total number of n_indices different colors is needed from the gradient, this method returns the index-th color.
functiongradient_cmyk(f_c, f_m, f_y, f_k)¶
functiongradient_hsb(f_g, f_s, f_b)¶
functiongradient_rgb(f_r, f_g, f_b)¶
This class provides an arbitray transition between colors of the same color model.
The functions f_c, etc. map the values [0, 1] to the respective components of the color model.
These factory functors for the corresponding functiongradient_ classes provide a linear transition between two given instances of the same color class. The linear interpolation is performed on the color components of the specific color model.
mincolor and maxcolor must be colors of the corresponding color class.
This class takes an arbitrary gradient and converts it into one in the RGB color model. This is useful for instance in bitmap output, where only certain color models are supported in Postscript/PDF.
This class takes an arbitrary gradient and converts it into one in the CMYK color mode. This is useful for instance in bitmap output, where only certain color models are supported in Postscript/PDF.
Instances of this class will make drawing operations (stroking, filling) to
become partially transparent. value defines the transparency factor in the
0 (opaque) to
Transparency is available in PDF output only since it is not supported by PostScript. However, for certain ghostscript devices (for example the pdf backend as used by ps2pdf) proprietary PostScript extension allows for transparency in PostScript code too. PyX creates such PostScript proprietary code, but issues a warning when doing so.