masking

@synthesize croppedImage;


- (void)viewDidLoad {
    [super viewDidLoad];

    NSString *inputPath = [[NSBundle mainBundle] pathForResource:@"images" ofType:@"png"];
    NSString *maskPath = [[NSBundle mainBundle] pathForResource:@"Unknown" ofType:@"png"];
    UIImage *inputImage = [[UIImage alloc] initWithContentsOfFile:inputPath];
    UIImage *mask = [[UIImage alloc] initWithContentsOfFile:maskPath];
    UIImage *cutOut = [self maskImage:inputImage withMask:mask];
    croppedImage.image = cutOut;
}

- (UIImage*) maskImage:(UIImage *) image withMask:(UIImage *) mask
{
    CGImageRef imageReference = image.CGImage;
    CGImageRef maskReference = mask.CGImage;

    CGImageRef imageMask = CGImageMaskCreate(CGImageGetWidth(maskReference),
                                             CGImageGetHeight(maskReference),
                                             CGImageGetBitsPerComponent(maskReference),
                                             CGImageGetBitsPerPixel(maskReference),
                                             CGImageGetBytesPerRow(maskReference),
                                             CGImageGetDataProvider(maskReference),
                                             NULL, // Decode is null
                                             YES // Should interpolate
                                             );

    CGImageRef maskedReference = CGImageCreateWithMask(imageReference, imageMask);
    CGImageRelease(imageMask);

    UIImage *maskedImage = [UIImage imageWithCGImage:maskedReference];
    CGImageRelease(maskedReference);

    return maskedImage;
}