How to render a CALayer with a different blending mode, like screen or multiply?

Question

I have a UIImageView and want it to be displayed with a specific blend mode. I know the iPhone has different blend modes, and it's probably possible to do it with a lot of CG code… but maybe there's a nice way with the CALayer of UIImageView?

score 7 · Answer 1 · answered Mar 22 '17 at 20:39

7

Set the compositingFilter of a view's layer to a supported blend mode string. From the docs, a layer's compositingFilter is

A CoreImage filter used to composite the layer and the content behind it.

To obtain a list of Core Image filters, print out the filter names defined by a kCICategoryCompositeOperation

[CIFilter filterNamesInCategory:kCICategoryCompositeOperation]

or directly as

[CIFilter filterNamesInCategory:@"CICategoryCompositeOperation"]

The array will include Core Image filters in the form

{
   CIColorBlendMode,
   CIColorBurnBlendMode,
   CIColorDodgeBlendMode,
   CIMultiplyBlendMode,
   ...
}

To use the CIMultiplyBlendMode, set "multiplyBlendMode" as the compositingFilter on the layer

self.layer.compositingFilter = @"multiplyBlendMode";

answered Mar 22 '17 at 20:39

bdev

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Complete list of filters is [here](https://developer.apple.com/library/content/documentation/GraphicsImaging/Reference/CoreImageFilterReference/index.html#//apple_ref/doc/uid/TP30000136-SW71). – bfx Feb 19 '18 at 13:27
6

Since the question is about iOS, beware, though, that Apple states in the documentation for `compositingFilter`: "This property is not supported on layers in iOS." – bfx Feb 19 '18 at 13:33
4

Strange that the documentation says that it's not supported on iOS, but it does appear to work as shown by this sample project: https://github.com/arthurschiller/CompositingFilters – Luke Rogers May 21 '18 at 09:54
This definitely works. I was able to recreate this from the github project listed above. I think the key factor that make this work is the hierarchy of the views: the subview is the one that needs the `compositingFilter`, not the parent view. – Merricat Sep 23 '20 at 19:28
Did you set the imageView layer? – João Nunes Aug 31 '23 at 13:44

score 1 · Accepted Answer · edited May 23 '17 at 10:30

1

see here: composite colors: CALayer and blend mode on iPhone

edited May 23 '17 at 10:30

Community

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answered Jul 13 '10 at 20:37

humasect

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5
9

How to render a CALayer with a different blending mode, like screen or multiply?

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