Mask a view in Objective-C

Question

In ActionScript 3 we can apply a mask of to a visual object like this:

SomeVisualObject.mask = maskShapeObject;

How can I achieve similar result in Objective-C? Assume I have two UIImageView objects, I want something like this:

imageView1.mask = imageView2;

How can I use one UIImageView to mask, or clip the shape of, another?

Read up on the compositing operations available when drawing UIImage objects. Sounds like you want the "source over" mode. — NSResponder, Jul 16 '12 at 11:31
possible duplicate of [How to mask UIViews in iOS](http://stackoverflow.com/questions/4559743/how-to-mask-uiviews-in-ios) — Monolo, Jul 16 '12 at 13:54

score 6 · Accepted Answer · answered Jul 16 '12 at 10:45

6

CALayer *maskLayer = [CALayer layer];
 UIImage *maskImage = [UIImage imageNamed:@"maskImage.png"];
maskLayer.contents = (id)maskImage.CGImage;
maskLayer.bounds = (CGRect){CGPointZero, maskImage.size};

UIImageView *imageViewToMask = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 1024, 768)];
imageViewToMask.image = [UIImage imageNamed:@"image2.png"];
imageViewToMask.layer.mask = maskLayer;

answered Jul 16 '12 at 10:45

msk

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It nearly works, but it seems like the mask has been positioned to the top left of the image, at location (-halfmaskwidth, -halfmaskheight). – Danyal Aytekin Jul 20 '13 at 23:24
... turns out it works for me with `frame`, not with `bounds`. – Danyal Aytekin Jul 21 '13 at 12:46
@DanyalAytekin =) HTH – msk Jul 21 '13 at 16:50

Mask a view in Objective-C

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