iOS UIImage Masking!

UIImage+DBMaskedImageAdditions.h

#import <UIKit/UIKit.h>

@interface UIImage (DBMaskedImageAdditions)

- (UIImage *)maskedImageWithMask:(UIImage *)maskImage;

@end

UIImage+DBMaskedImageAdditions.m

#import "UIImage+DBMaskedImageAdditions.h"

@implementation UIImage (DBMaskedImageAdditions)

- (UIImage *)maskedImageWithMask:(UIImage *)maskImage
{
    CGImageRef maskImageRef = maskImage.CGImage; 
    
    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskImageRef),
                                        CGImageGetHeight(maskImageRef),
                                        CGImageGetBitsPerComponent(maskImageRef),
                                        CGImageGetBitsPerPixel(maskImageRef),
                                        CGImageGetBytesPerRow(maskImageRef),
                                        CGImageGetDataProvider(maskImageRef), NULL, false);
    
    CGImageRef sourceImage = self.CGImage;
    CGImageRef maskedImage;
    
    CGImageAlphaInfo alpha = CGImageGetAlphaInfo(sourceImage);
    
    if (alpha != kCGImageAlphaFirst && alpha != kCGImageAlphaLast && alpha != kCGImageAlphaPremultipliedFirst && alpha != kCGImageAlphaPremultipliedLast) {
        size_t width = CGImageGetWidth(sourceImage);
        size_t height = CGImageGetHeight(sourceImage);
        
        CGContextRef offscreenContext = CGBitmapContextCreate(NULL, width, height,
                                                              8, 0, CGImageGetColorSpace(sourceImage),
                                                              kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
        
        CGContextDrawImage(offscreenContext, CGRectMake(0, 0, width, height), sourceImage);
        
        CGImageRef imageRefWithAlpha = CGBitmapContextCreateImage(offscreenContext);
        maskedImage = CGImageCreateWithMask(imageRefWithAlpha, mask);
        CGImageRelease(imageRefWithAlpha);
        
        CGContextRelease(offscreenContext);
    } else {
        maskedImage = CGImageCreateWithMask(sourceImage, mask);
    }
    
    UIImage *returnImage = [UIImage imageWithCGImage:maskedImage];
    
    CGImageRelease(maskedImage);
    CGImageRelease(mask);
    
    return returnImage;
}

@end