Newsgroups: comp.sys.mac.programmer
Path: utzoo!utgpu!watserv1!maytag!daemon
From: cgh@csg.UWaterloo.CA (Christopher G. Healey)
Subject: PICT file format
Message-ID: <1990Jul23.153137.12877@maytag.waterloo.edu>
Sender: daemon@maytag.waterloo.edu (Admin)
Organization: Computer Systems Group, U of Waterloo
Date: Mon, 23 Jul 90 15:31:37 GMT
Lines: 28


   We're trying to get information on the format of PICT files, specifically
how bitmap images are saved in a PICT file.

   We have to convert a number of PC screen image files into Macintosh PICT
files on a PC. We need to write a conversion utility which will generate
a PICT file. Unfortunately, for a number of reasons, we cannot move the PC
image files to the Mac and create the PICT file there, it must be done on
the PC.

   TechNotes #21 gives a brief explination of the PICT format, and states
that CopyBits is used to represent bitmap images. However, there are still
a number of unanswered questions, namely:

 - When a CopyBits command is stored in a PICT file, how is the bitmap
   data itself stored? It seems that simple byte stuffing (8 pixels per
   byte) is used up to a certain image size, but that PackBits is used
   for larger images. If this is true, at what image size is PackBits used?

 - How large can a single CopyBits image be? IM says it should be no
   larger than 3K (this means we would have to use a number of CopyBits
   commands to represent the whole image). Does this limit also apply
   to PICT files?

   Any information or references would be greatly appreciated.

Christopher G. Healey
(cgh@csg.uwaterloo.ca)