How to show in UIImage just a part of image?

Question

I have UIImageView in which I\'m showing 50x100 image.

I want to show only a part of image 50x50 (top part)?

How can I do that?

Answer 1

You can crop the image by using CGImageCreateWithImageInRect, which is Quartz primitive working on CGImageRef, so you would have something like:

CGImageRef imageRef = CGImageCreateWithImageInRect(originalImage.CGImage, cropRect);
UIImage* outImage = [UIImage imageWithCGImage:imageRef scale:originalImage.scale orientation:originalImage.imageOrientation]]; 
CGImageRelease(imageRef);

When calculation cropRect, keep in mind that it should be given in pixels, not in points, i.e.:

float scale = originalImage.scale;
CGRect cropRect = CGRectMake(0, 0,
                         originalImage.size.width * scale, originalImage.size.height * 0.5 * scale);

where the 0.5 factor accounts for the fact that you want the top half only.

If you do not want to go low-level, you could add your image to a UIView as a background color and use the clipToBounds CALayer property to make the clipping:

myView.backgroundColor = [UIColor colorWithBackgroundPattern:myImage];
myView.layer.clipToBounds = YES;

also, set myView bounds accordingly.