ASCII art

From: John Wilson <wilson_at_dbit.dbit.com>
Date: Thu May 25 12:19:16 2000

On Thu, May 25, 2000 at 12:12:58AM -0700, Doug Coward wrote:
> A couple of years ago, after reading the chapter on ASCII art
> in "The New RTTY Handbook", I wrote a quick and dirty program
> to to convert .BMP files into non-overstrike ASCII pictures
> I could send in emails. From the book, I created my levels of
> "gray" in 8 levels with this character array:
> M H I : " , . [SP] (from dark to light)

Do any of the line printer art programs attempt to distribute the error to
neighboring pixels? I always assumed those systems (the commercial ones
anyway, like the outfits that used to make line-printer T-shirts from photos)
used something like Floyd-Steinberg halftoning, where you use the value of
the current pixel to choose a level of gray, then figure out by how much
that level differs from the value you *really* wanted, and distribute that
error to neighboring pixels which you'll visit later on in the sequence.
Having a cumulative error of only one level of gray per line lets you get
really nice pictures from lousy output devices, all with integer math...

John Wilson
D Bit
Received on Thu May 25 2000 - 12:19:16 BST