🚀 go-pugleaf

The difference between the difference between printing white
and not printing anything.

PostScript does the best it can with the device resolution it's
got: in particular, very thin lines will get slightly thicker
if they are down at the sub-pixel size. This applies whichever
coolur is being used, and so if you want a "picture frame"
effect with a thick black line, a thin white line and a thin
black line. e.g.

        BBBBBBBBBBB
        BBBBBBBBBBB
        wwwwwwwwwww
        BBBBBBBBBBB

then the most "size independent" way of doing it is to print a
width 4 black line, with a width 1 white line on top. When this
is drawn small, the white line is the one which gets the
benefit of rounding up to pixel size. If this is drawn realy
small, the white line will eventually completely obscure the
black line.

With the bitmap, all of the black and white pixels are draw
simultaneously, so they all get an equal chance of affecting
any given pixel (plus there might be some special purpose
handling since bitmaps are so well defined) and you get a
balance between the black and white.

What you do about this difference is another matter - even
doing some scaling inside Illustrator won't actually fix the
problem of rendering things successively. This is intriguing
because it is a further extension of the separation of
description from rendering: the notion of path allows you to
describe a single path and then render it in one colour, but
the bitmap allows you to describe in lots of colours and then
render as one operation.
-- 

William Roberts         ARPA: liam@cs.qmc.ac.uk  (gw: cs.ucl.edu)
Queen Mary College      UUCP: liam@qmc-cs.UUCP
LONDON, UK              Tel:  01-975 5250