I m trying to take my gl buffer and turn it into a UIImage while retaining the per-pixel alpha within that gl buffer. It doesn t seem to work, as the result I m getting is the buffer w/o alpha. Can anyone help? I feel like I must be missing a few key steps somewhere. I would really love any advice on this.

Basically I do:

//Read Pixels from OpenGL
glReadPixels(0, 0, miDrawBufferWidth, miDrawBufferHeight, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

//Make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, len, NULL);

//Configure image
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGImageRef iref = CGImageCreate(miDrawBufferWidth, miDrawBufferHeight, 8, 32, (4 * miDrawBufferWidth), colorSpaceRef, kCGBitmapByteOrderDefault, provider, NULL, NO, kCGRenderingIntentDefault);

// use device s orientation s width/height to determine context dimensions (and consequently resulting image s dimensions)
uint32* pixels = (uint32 *) IQ_NEW(kHeapGfx, "snapshot_pixels") GLubyte[len];

// use kCGImageAlphaLast? :-/
CGContextRef context = CGBitmapContextCreate(pixels, iRotatedWidth, iRotatedHeight, 8, (4 * iRotatedWidth), CGImageGetColorSpace(iref), kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);


CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, miDrawBufferWidth, miDrawBufferHeight), iref);
UIImage *outputImage = [[UIImage alloc] initWithCGImage:CGBitmapContextCreateImage(context)];

//cleanup
CGDataProviderRelease(provider);
CGImageRelease(iref);
CGContextRelease(context);

return outputImage;