Re: Printing MAC bitmaps on GS

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <3hc7la$ckk@gap.cco.caltech.edu>,
Nathan Mates <nathan@cco.caltech.edu> wrote:
> 
> >In general no paint program stores bitmap files at 300 dpi, and
> >further, 300 dpi bitmaps are never chugged over an AppleTalk line to
> >a LaserWriter.  
> 
>    Heck yes they do and are. Superpaint 3.x (and probably earlier
> versions) naturally does stuff at 300 dpi. And things are sent at 300
> dpi to a Laserwriter: pictures and non-native fonts. (Fonts that the
> LW has in ROM can be sent as ascii, but everything else is downloaded
> as a 300dpi bitmap). 
> 
>    Ever print a 300dpi postscript file to any printer? It takes a
> while.  That's because you're shoving 17x the info at the printer, and
> the printer has to deal with 17x the info.

Wrong.  If you are printing a Postscript file, Postscript commands are
sent to the printer.  The printer is responsible for rendering the
graphical data in the appropriate resolution.  The higher the
resolution, the more data the printer has to generate, and the longer
it takes.

If you are printing to a Postscript printer with Apple's LaserWriter
driver (IIgs or Mac), QuickDraw calls are transformed into Postscript
commands.  The only data which is sent to the printer as a raw bitmap
is a pixel map or a font which is only available in bitmap form.

>    If the Mac host program can only handle 72dpi, it prints to the
> printer driver at 72 dpi. If it's got a 300dpi printout, it feeds
> the driver a 300dpi image, which is then sent to the LW at that
> resolution. If the driver gets a 72 dpi image, then either it or
> the LW (not sure which) converts it to 300dpi before printing.

Probably the driver.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand