I've used libpng directly with very little pain. I imagine you could
also use DevIL or some OSS library too.
That being said, it's appalling to me that CG offers
kCGImageAlphaFirst but doesn't actually implement it.
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On May 14, 2007, at 5:05 PM, Andy O'Meara wrote:
As OGLers here know, one regularly needs to upload textures that
have an alpha channel (with non-multiplied RGB). Meanwhile,
CGBitmapContextCreate() doesn't support kCGImageAlphaFirst (see
Apple QA 1037), which makes CGBitmapContextCreate() utterly useless
for getting true image RGBA data from a CGImage (see QA1509). Am I
going nuts or is this kind of ridiculous for anyone loading images
in to be used as textures (with alpha) in OpenGL?
Given this, what's the best-performance way to upload images from
arbitrary image files? High performance and low overhead is
critical since we can't keep all the textures that we use memory
resident.
I don't appear to be the only one running into this...
I got into this mess because I wanted to move away from all the
deprecated (GWorld) stuff. Now it looks GraphicsImportSetGWorld()
is the only way to get the non-premultiplied image data. So much
for leaving QuickDraw...
Any recommendations would be kindly appreciated.
Thanks,
Andy
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