iOS Setting individual pixel values in a UIImageView

[neuronrev]

Recently I needed to figure out how to set individual pixel color values in a UIImageView. I couldn't find any example on how to do this, so I thought I'd post how I eventually did it.

The following code snippet takes a UIImageView and sets each pixel in the image to a random color. Not very exciting but it shows one approach to setting individual pixel values.

If anyone knows a better way to do this, or how to improve my code, please post.

- (void)RandomizePixelColors:(UIImageView *)imageView
{	
    size_t w = imageView.image.size.width;
    size_t h = imageView.image.size.height;
	
    // 4 bytes per pixel
    int numBytes = 4 * w * h;
	
    unsigned char* pixelData = (unsigned char*)malloc(numBytes * sizeof(unsigned char));

    // This loop sets each pixel as a set of 4 bytes
    for(int i = 0; i < numBytes; i += 4)
    {
        int red = i;
        int green = i+1;
        int blue = i+2;
        int alpha = i+3;
		
        pixelData[red] = (arc4random() % 255);
        pixelData[green] = (arc4random() % 255);
        pixelData[blue] = (arc4random() % 255);
        pixelData[alpha] = 255;
    }

	
    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, pixelData, numBytes, NULL);
	
    CGImageRef newImageRef = CGImageCreate (
                                             w,
                                             h,
                                             8,
                                             8*4,
                                             4*w,
                                             colorspace,
                                             kCGBitmapByteOrderDefault,
                                             provider,
                                             NULL,
                                             false,
                                             kCGRenderingIntentDefault
                                             );
	
    imageView.image = [UIImage imageWithCGImage:newImageRef];
	
    CGColorSpaceRelease(colorspace);
    CGDataProviderRelease(provider);
    CGImageRelease(newImageRef);	
}