Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!farrier
From: farrier@Apple.COM (Cary Farrier)
Newsgroups: comp.sys.apple
Subject: Re: Apple IIgs SHR fade
Keywords: fade, IIgs, SHR
Message-ID: <30927@apple.Apple.COM>
Date: 17 May 89 15:33:50 GMT
References: <11472@bloom-beacon.MIT.EDU>
Distribution: usa
Organization: Apple Computer Inc, Cupertino, CA
Lines: 34

In article <11472@bloom-beacon.MIT.EDU> mhamaoka@athena.mit.edu (Michael T Hamaoka) writes:
> [stuff about fading a SHR screen deleted]

	You should probably get access to the Apple IIGS Hardware Reference 
	(This one *is* published by Addison Wesley, ISBN 0-201-17743-9), and
	start reading on page 84, Super Hi-Res graphics.  It will tell you
	all you need to know about how SHR mode operates.

	About the fading, try this algorithm to fade to black:

	for(loop = 0 to 15)
	{
		for (each color entry in the palette)
		{
			if(red_value - 1 > 0 )
				decrement the red value;
			if(green_value - 1 > 0 )
				decrement the green value;
			if(blue_value - 1 > 0 )
				decrement the blue value;
		}		
	}

	This loop will decrement the RGB values of each color register
	to zero, thus fading to black.  This is not the best algorithm,
	a better one would be one that would examine all the entries
	in the color palette and then figure out the amount to decrement
	each to produce an even fade simultaneously.

	To fade in, simply reverse the process, incrementing each
	RGB gun until it reaches it's maximum value for the color
	desired.

Cary Farrier