Hi, 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;