The method below will take your original image and the mask image (the black shape) and return a UIImage
that includes only the content of the image covered by the mask:
+ (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;
}
The areas outside the mask will be transparent. You can then combine the resulting UIImage
with a background color.