Black dots in PostScript print outs

[Chris L. Fouts 754-3298]

In message <9008272215.AA25131 at max>; from "Harmon J. Zuccola" on Aug 27, 90
6:15 pm, Harmon writes:
> 
> 	3) How do you get rid of those little grey dots, when you know
> you should have a white background [on PostScript plots]?
> 			
I assume you are using the tops program.  The source for this program is
included in /usr/people/4Dgifts/iristools/imgtools.  The problem is in the
rgbrowtobw routine at the bottom of the file.  Change the following line

            *obuf++ = (77*(*rbuf++) + 150*(*gbuf++) + 28*(*bbuf++))>>8;

to

            *obuf++ = (77*(*rbuf++) + 150*(*gbuf++) + 29*(*bbuf++))>>8;
						      ^^
and re-compile it.

As it is, any white pixels (rbuf=gbuf=bbuf=255) cause obuf to be loaded
with the value of 254 instead of 255.  The printer prints out this
"almost-white" color using a very light dither pattern, resulting in the
black dots.

--------------------------------------------------------------------------------
Chris L. Fouts				Email: fouts at inetg1.arco.com
Systems Engineer			Phone: 214-754-3850
Silicon Graphics Computer Systems
--------------------------------------------------------------------------------
"I have never seen anything fill up a vacuum so fast and still suck."
							- Rob Pike on X
--------------------------------------------------------------------------------