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MathGroup Archive 1991

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gray levels

  • To: mathgroup at yoda.ncsa.uiuc.edu
  • Subject: gray levels
  • From: karl at park.bu.edu (Karl Frederick Arrington)
  • Date: Mon, 25 Feb 91 12:00:31 -0500

I am running: Sun-4 (SunOS) 1.2 (November 6, 1989).  I would like to
draw an image with at least 256 gray levels, but I only seem to get 32
levels, which looks like luminance steps rather than a smooth ramp.  I
remeber being able to change (increase the gray range of) the color
map for Mma on the Mac, but haven't figured out how on the Sun-4.  I
tried it w/ and w/o (1) $AlwaysUsePrivateColorMap = True; and (2)
{PlotColor -> False}, but this still only provides 32 levels, even
though I'm specifying many more levels:

$AlwaysUsePrivateColorMap = True;

tg = Flatten[ Table[    { GrayLevel[n/10.0], Line[{{n,-1},{n,1}}] },
                        {n,0,10,0.025} ] ];

Show[ Graphics[ tg ], {PlotColor -> False} ];

------------------------------------------------------------------------------
Karl Frederick Arrington                 Private: 617-353-6181
Center for Adaptive Systems               Office: 617-353-7857
Cognitive and Neural Systems Program       email: karl at park.bu.edu  (ARPANET)
Boston University
111 Cummington Street, Second Floor
Boston, Massachusetts  02215  USA
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