Re: Printing MAC bitmaps on GS

[lstrand@clyde.ics.uci.edu (Leif Strand)]

In article <3h34gd$6u3@gap.cco.caltech.edu>,
Nathan Mates <nathan@cco.caltech.edu> wrote:
>   Bitmaps are naturally chunky; that's why people would much prefer
>to stay away from most of them. But, especially on Macs, bitmaps can
>be provided at 300dpi, or printer resolution. If you display that to
>the screen, the quality remains 300dpi internally, but is displayed at
>only 72dpi because that's all the screen can handle. By clipping that
>screen, and converting it to the GS, the quality remains at 72dpi.
>
>   If you were to print it at this point, the Mac still has the 300dpi 
>info to print it nicely, but the GS has 1/16 the data (1/4 in both
>horizontal and vertical) to work with. 

Bitmaps on the Mac are always 72 dpi -- "internally", on screen, and when
printed.  We are talking about MacPaint, right?  Who ever heard of 300 dpi
MacPaint files?  Ask Bill Atkinson -- his program ran on the original 128K Mac;
somehow I doubt that there was enough free memory available to store a full-
page, 300 dpi bitmap "internally" -- but then he _was_ a wizard; I could be
wrong.

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.  The
high resolution of a laser printer is internal to the printer and is produced
in response to geometric PostScript commands issued from a shape-oriented
"draw" program such as MacDraw.  But bitmaps from a "paint" program such as
MacPaint are still printed at 72 dpi, even on laser printer.

The reason why the print resolution of the GS is so low is because the screen
resolution is so low, and any WYSIWYG printout has to display a chunkyness
that resembles the screen somewhat.  Also a printer such as the ImageWriter II
can only print 8 colors so you need larger pixels to simulate all the colors/
halftones possible on the screen, using dithering.

If you abandon WYSIWYG, by selecting "Condensed" in the "Page Setup" dialog
when printing a 640 mode graphic, the printout will only comically resemble
what is displayed on the screen, but the print resolution will be 72 dpi, like
the Mac.  The trick to printing a MacPaint file nicely is getting a conversion
of it that is stretched vertically just like fonts are on-screen, and then
print it in condensed mode -- or, alternatively, getting a gigantic 320 mode
conversion that isn't stretched and printing it at 50% reduction (but not
condensed).

--Leif Strand