ios basic image processing extract red channel

Question

straight forward I need to extract color components from an image, usually in Matlab this is done choosing the first matrix for Red.

In the realm of accelerate framework, which documentation is reference-based I can't find an easy way of doing this without resolving to graphics context.

Thanks in advance!!

Answer 1

UIImage* image = // An image
CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage));
const UInt8* pixelBytes = CFDataGetBytePtr(pixelData);

//32-bit RGBA
for(int i = 0; i < CFDataGetLength(pixelData); i += 4) {
    pixelBytes[i]   // red
    pixelBytes[i+1] // green
    pixelBytes[i+2] // blue
    pixelBytes[i+3] // alpha
}