pixelsFromImage.m

-(void) pixelsFromImage:(NSImage*)image
         withCompletion:(void(^)(UInt32 *pixels, NSUInteger pixelCount))completion {
    
    //Extract pixels from the image in a 1D array
    CFDataRef inputData = (__bridge CFDataRef)[image TIFFRepresentation];
    CGImageSourceRef inputSource = CGImageSourceCreateWithData(inputData, NULL);
    CGImageRef inputCGImage = CGImageSourceCreateImageAtIndex(inputSource, 0, NULL);
    NSUInteger width = CGImageGetWidth(inputCGImage);
    NSUInteger height = CGImageGetHeight(inputCGImage);
    NSUInteger numberOfPixels = height * width;
    
    NSUInteger bytesPerPixel = 4;
    NSUInteger bytesPerRow = bytesPerPixel * width;
    NSUInteger bitsPerComponent = 8;
    
    //Store all pixels in this array
    UInt32 * pixels;
    pixels = (UInt32 *) calloc(numberOfPixels, sizeof(UInt32));
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pixels, width, height,
                                                 bitsPerComponent, bytesPerRow,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    
    //Fill in the pixels array
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), inputCGImage);
    
    //Cleanup
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    
    if (completion) {
        completion(pixels, numberOfPixels);
    }
}