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From: scott@sage.uchicago.edu (Scott Deerwester)
Newsgroups: comp.sys.next,comp.lang.postscript
Subject: A little PostScript hacking for NeXT screens
Message-ID: <3338@tank.uchicago.edu>
Date: 19 May 89 14:38:47 GMT
Sender: news@tank.uchicago.edu
Reply-To: scott@sage.uchicago.edu (Scott Deerwester)
Organization: TIRA / UofC
Lines: 62

I've been enjoying Scene in both 0.8 and 0.9.  As I write this, my
screen background is a photograph of a beach with palm trees... if I
could only get the DSP to do steel drums...  I've done a bit of
hacking in PostScript to diddle with the brightness and contrast of
images (in the sense of PostScript's "image" operator), and thought
that others might be interested in similar diddling.  To use this,
change x and y to the dimensions of your image, and bits to the number
of bits of grey scale (probably either 1 or 8).  Brightness ranges
from -1 to 1, with lower numbers being darker, and 0 applying no
transformation at all to the image.  Contrast is similar.  Small
positive values (ranging from 0.1 to 0.3) for both have given me the
best results, especially for images that began life as color photos.

Insert your bitmap (a Whole Big Bunch of hex numbers) at the
appropriate place.  Only caveat that I'm aware of is that if your
bitmap doesn't have as many elements as you said it did, you may
expect garbage to follow.

%!PS-Adobe-1.0
%%BoundingBox: 0.000 0.000 512.000 480.000
%
%	Author:
%		Scott Deerwester, University of Chicago
%	Copyright:
%		You may freely copy this code, provided that a copy
%		of this notice is included with all copies.
%
/x 512 def		% Number of columns
/y 480 def		% Number of rows
/bits 8 def		% Number of bits of grey scale
/brightness 0.3 def
/contrast 0.2 def
/picstr x string def
gsave
x y scale
{
%	Uncomment the following line if your image looks like a negative
%	1 exch sub
	brightness 0 ne
	{
		dup
		brightness 0 gt
		{
			1 exch sub
		} if
		9 mul 1 add log brightness mul
		1 brightness sub mul add
	} if
	contrast 0 ne
	{
		dup 360 mul sin contrast mul sub
	} if
}
settransfer
x y bits
[x 0 0 y neg 0 y]
{currentfile picstr readhexstring pop}
image

% Insert your bitmap here

grestore