Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!pacbell.com!ucsd!nic.cerf.net!happy.sdsc.edu!moreland
From: moreland@happy.sdsc.edu (John Moreland)
Newsgroups: comp.sys.mac.programmer
Subject: PICT BitMap/PixMap overlap
Summary: PICT BitMap/PixMap overlap
Keywords: PICT BitMap/PixMap overlap
Message-ID: <474@nic.cerf.net>
Date: 26 Jun 91 17:13:34 GMT
Sender: news@nic.cerf.net
Followup-To: moreland@sdsc.edu
Distribution: usa
Organization: San Diego Supercomputer Center @ UCSD
Lines: 31

Hello Knows-PICTers,

I need to know how to draw the bits of an "overlaping" PixMap/BitMap for
a PICT image.  I'm developing code to parse PICT images on a UNIX platform
and I need to know what to do with pixels from a PackPixRect or PackBitsRect
opcode that are the same as color as the "background" color.

If I draw a PixMap on top of some preveously drawn graphics and the PixMap
has "blank" areas (white), should all white pixels in the image be ignored
(in which case you could "see through" the white areas of the PixMap)
or should they be DRAWN as white (in which case the white pixels
overwrite any previously drawn graphics) ?

Does the PixMap's "penmode" (copybits transfer mode) tell me this ?  HOW ?
Does the current QuickDraw background color effect whether or not you can
"see through" a PixMap/BitMap ?  HOW ?

Please Help,
John

-- 
 _____                                                                   _____
( ___ )-----------------------------------------------------------------( ___ )
 |   |                                      ||    moreland@sdsc.edu      |   |
 |   |          />                          |+===========================|   |
 |   |         /<                  Kcah Cam || John L. Moreland          |   |
 |   | [\\\\\\(O):::<=====================- || San Diego Supercomputer   |   |
 |   |         \<       Fighter/Ma(gi)cUser ||    Center (SDSC)          |   |
 |   |          \>                          || AppleLink:  D6812         |   |
 |___|                                      || Phone: (619) 534-5170     |___|
(_____)-----------------------------------------------------------------(_____)