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Re: Preserving alpha channel in BMP to GWorld?

Subject: Re: Preserving alpha channel in BMP to GWorld?
From: Andreas Wittenstein <email@hidden>
Date: Sat, 18 Dec 2004 08:37:42 -0800
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Jim,

Try setting the 'cmpCount' of the GWorld to 4. Apple's BMP encoder doesn't support alpha, but if the decoder does, that should do the trick.

Andreas Wittenstein
BitJazz Inc.
http://www.bitjazz.com/sheervideo/

I have some BMP format data which contains an alpha channel. I am trying to load this image into a 32-bit GWorld (created with NewGWorld), and preserve the alpha channel in the upper byte of each pixel. At some later point I would then draw this GWorld using the alpha channel using DecompressImage() with one of the alpha transfer graphics modes. I've got the BMP graphics importer set up and drawing the image into the GWorld using GraphicsImportDraw(), but it doesn't preserve the alpha channel. Is there something special I need to do to get it to copy the alpha channel as well as the RGB data into the GWorld?
Thanks,
Jim


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