From: Nate Eldredge Newsgroups: comp.os.msdos.djgpp Subject: Re: Allegro - masked_blit(); Date: 20 Jan 2000 12:48:55 -0800 Organization: InterWorld Communications Lines: 28 Message-ID: <83r9fcv58o.fsf@mercury.st.hmc.edu> References: <867egt$dpf$1 AT barcode DOT tesco DOT net> NNTP-Posting-Host: mercury.st.hmc.edu X-Trace: nntp1.interworld.net 948401442 7489 134.173.45.219 (20 Jan 2000 20:50:42 GMT) X-Complaints-To: usenet AT nntp1 DOT interworld DOT net NNTP-Posting-Date: 20 Jan 2000 20:50:42 GMT X-Newsreader: Gnus v5.7/Emacs 20.4 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Reply-To: djgpp AT delorie DOT com "Paul Bibbings" writes: > Please could someone give me a few pointers in the use of this function. I'm > new to Allegro and I'm not getting very far with the available docs. > What I'm trying to do is simple enough, but I'm stuck with how to set > transparent pixels. My program simply draws a chessboard to the screen, then > accesses a single bitmap showing the chess pieces (black on a white > background). The question is, what do I need to do so that the masked_blit() > interprets the background as transparent, hence allowing the board to be > seen behind the pieces. > I've tried everything I can think of. Allegro.txt under masked_blit() > that transparent pixels are marked by a zero in 256 color modes, or bright > pink for truecolor data. Hi do I set the background color of the bitmap so > that the program will interpret it as zero and skip the background pixels? > (I've tried changing the background color to bright pink out of desperation, > but since the function set_palette() uses the palette derived from the > bitmap, then ALL the colours are changed from what I set them. You need to create your bitmap such that the "background" is actually in color 0 (whatever that corresponds to in your pallete). Your paint program (or whatever you use) should have a way to do this. If not, you probably want to find one that does. -- Nate Eldredge neldredge AT hmc DOT edu