From: Shawn Hargreaves Newsgroups: comp.os.msdos.djgpp Subject: Re: Please Help: Allegro 3.0 beta Date: Mon, 24 Nov 1997 23:47:42 +0000 Organization: None Distribution: world Message-ID: References: <347A03FB DOT 4A0B AT voyageur DOT ca> NNTP-Posting-Host: talula.demon.co.uk MIME-Version: 1.0 Lines: 42 To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Precedence: bulk J.E. writes: >1. AFAIK, the docs say that true color images don't use palettes, but >the RGB values are stored directly in the pixels (video mem, I guess). >So how many R, G, or B values are there (63? 255?)? That depends on the color depth. In 24 or 32 bit modes there are 8 bits each of red, green, and blue, so you have 256 levels of each color component (the 32 bit modes are the same as 24 bits, but with an added pad byte to keep things aligned and make them go faster). In a 15 bit mode there are 5 bits of each color (32 shades), and the 16 bit modes use a 5.6.5 layout (5 bits or 32 shades of red and blue and 6 bits or 64 shades of green). >Also, how to I specify a color to use during drawing primitives (like >putpixel) if there is no palette? Use the makecol() function. See ex29.c... >2. Now for my next question: How do I create a reasonably fast double >buffering system in true color (24-bit)? I tried using the usual >method (scan under sprites, draw to buffer, blit buffer to screen, >erase sprites), but it's *extremely* slow on my Cyrix 5x86 75mhz Get a faster PC :-) A 640x480x24 image is nearly a megabyte of data: that is a huge amount to be copying on every frame! Using a 15 or 16 bit mode will help (those are usually much faster to draw than the 24 bit resolutions as well, due to better pixel alignment), and if possible you should try to use some kind of double buffer system and only blit the regions that have changed from one frame to the next... >And now my final question: How do I use a transparent color to draw >24-bit sprites? Allegro uses bright magenta (maximum red and blue, zero green) as a special marker color, in exactly the same way as color #0 in the 256 color modes. -- Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/ "Pigs use it for a tambourine" - Frank Zappa