Re: [PyX-user] use of functionpalette?

[Michael S. <mic...@ph...>]

Hello Alan,

On 26.05.06, Alan G Isaac wrote:
> On Fri, 26 May 2006, Michael Schindler apparently wrote: 
> > The BlackYellow palette is optimized to yield good results 
> > print out in grayscales (this is especially important when 
> > publishing in color-online scientific journals) 
> 
> Is this theory based or trial and error.
> If the former, can you post a reference.

sorry for the late answer, I was busy the last few days...

The conversion of colors into grayscales is not quite straightforward.
On any reasonable Postscript device, however, the conversion rule
defined in the Postscript standard should be applied. This means

  RGB -> GRAY:
    GRAY = 0.3*R + 0.59*G + 0.11*B

Similar things can be defined for CMYK -> GRAY. A good reference on
these things is the documentation for the LaTeX package xcolor.sty.

A good color palette has a linear dependence of the such defined gray
value on the parameter. This is not exactly the case with BlackYellow,
but nearly. You can play with differently defined palettes in the file

 <PYX-SVN>/design/palettetest.py


Michael.

-- 
"A mathematician is a device for turning coffee into theorems"
  Paul Erdös.