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Masking of Image on another image

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Here is a small core graphics method for masking of images:


– (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

CGContextRef mainViewContentContext;
CGColorSpaceRef colorSpace;

colorSpace = CGColorSpaceCreateDeviceRGB();

// create a bitmap graphics context the size of the image
mainViewContentContext = CGBitmapContextCreate (NULL, image.size.width, image.size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);

// free the rgb colorspace

CGImageRef maskingImage = [maskImage CGImage];
CGContextClipToMask(mainViewContentContext, CGRectMake(0, 0, maskImage.size.width, maskImage.size.height), maskingImage);
CGContextDrawImage(mainViewContentContext, CGRectMake(0, 0, image.size.width, image.size.height), self.CGImage);

// Create CGImageRef of the main view bitmap content, and then
// release that bitmap context
CGImageRef mainViewContentBitmapContext = CGBitmapContextCreateImage(mainViewContentContext);

// convert the finished resized image to a UIImage
UIImage *theImage = [UIImage imageWithCGImage:mainViewContentBitmapContext];
// image is retained by the property setting above, so we can
// release the original

maskingImage = nil;
// return the image
return theImage;


For more detail about masking please checkout Quartz 2D developer guide:


!! Enjoy !!