Applying a CIFilter to a CALayer

问题

CI Filters are now available in iOS 5, and I'm trying to apply one to a CALayer, the way you'd do it on Mac. Here's my code:

CALayer *myCircle = [CALayer layer];
myCircle.bounds = CGRectMake(0,0,30,30);
myCircle.position = CGPointMake(100,100);
myCircle.cornerRadius = 15;
myCircle.borderColor = [UIColor whiteColor].CGColor;
myCircle.borderWidth = 2;
myCircle.backgroundColor = [UIColor whiteColor].CGColor;

CIFilter *blurFilter = [CIFilter filterWithName:@"CIDiscBlur"];
[blurFilter setDefaults];
[blurFilter setValue:[NSNumber numberWithFloat:5.0f] forKey:@"inputRadius"];
[myCircle setFilters:[NSArray arrayWithObjects:blurFilter, nil]];

[self.view.layer addSublayer:myCircle];

My white circle draws fine, but the filter isn't applied.

回答1:

Aside from the fact that CIDiskBlur is not available (as of iOS SDK 5.1) and that setFilters: seems to be not available either you could do the following:

Create the input CIImage from the contents of your layer:

CIImage *inputImage = [CIImage imageWithCGImage:(CGImageRef)(myCircle.contents)];`

Apply your filters and get the result in an CGImageRef:

CIFilter *filter = [CIFilter filterWith...];// A filter that is available in iOS or a custom one :)
...
CIImage *outputImage = [filter outputImage];
CIContext *context = [CIContext contextWithOptions:nil];
CGImageRef cgimg = [context createCGImage:outputImage fromRect:[outputImage extent]];

Finally set the CGImageRef to the layer:

[myCircle setContents:(id)cgimg];

This should work :)

来源：https://stackoverflow.com/questions/9701358/applying-a-cifilter-to-a-calayer