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CoreImage snippet for UIImage blurring
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| // | |
| // CoreImage filter chain to blur an arbitrary UIImage | |
| // Input: blur radius and target size | |
| // This is assumed to be called on a background queue, it takes a response block to process the completed, blurred image | |
| // <C> 2013/2014 Joerg Schwieder, use at will; I'd love to see an attribution, of course but don't demand it. | |
| // Contains some pseudo code, see comments. | |
| // | |
| + (CGFloat)blurRadius { | |
| static CGFloat _blurRadius = 20.0; | |
| static dispatch_once_t onceToken; | |
| // I use different blur radius on iPad and iPhone | |
| dispatch_once(&onceToken, ^{ | |
| if (IS_ON_PAD) | |
| _blurRadius *= 2.0; | |
| }); | |
| return _blurRadius; | |
| } | |
| + (CGFloat)filteredSize { | |
| static CGFloat _filteredSize = 320.0; | |
| static dispatch_once_t onceToken; | |
| // I use different image sizes on iPad and iPhone. | |
| // This can, of course, be variable, too, it's being set dynamically on the filter for each run but that filter change takes some time | |
| // I also use non-retina resolution because I felt that the lower resolution goes unnoticed (for the blurred image) on retina screens and it cuts the processing by 75% | |
| dispatch_once(&onceToken, ^{ | |
| if (IS_ON_PAD) | |
| _filteredSize = 768.0; | |
| }); | |
| return _filteredSize; | |
| } | |
| + (void)createBlurredImage:(UIImage *)art | |
| withTintColor:(UIColor *)blendColor | |
| desaturationFactor:(CGFloat)desaturationFactor | |
| completion:(void(^)(UIImage * source, UIImage * result))completionHandler; | |
| { | |
| static CIFilter * ciBlurFilter; | |
| static CIFilter * ciColorControlFilter; | |
| static CIContext * ciContext; | |
| static CIFilter * ciColorGenerator; | |
| static CIFilter * ciCompositor; | |
| static dispatch_queue_t filterQueue; | |
| // this initializatuon code needs to be run on the main thread. | |
| // I use a macro to determine which thread I'm on (I use specific queues I can identify at runtime). | |
| // If you don't have that you could add the whole code to a custom class and simply initialize it before use | |
| dispatch_sync_safe(dispatch_get_main_queue(), ^{ | |
| static dispatch_once_t onceToken; | |
| dispatch_once(&onceToken, ^{ | |
| ciContext = [CIContext contextWithOptions:nil]; | |
| ciBlurFilter = [CIFilter filterWithName:@"CIGaussianBlur"]; | |
| ciColorControlFilter = [CIFilter filterWithName:@"CIColorControls"]; | |
| //[ciColorControlFilter setValue:@(desaturationFactor) forKey:@"inputSaturation"]; | |
| ciColorGenerator = [CIFilter filterWithName:@"CIConstantColorGenerator"]; | |
| ciCompositor = [CIFilter filterWithName:@"CISourceOverCompositing"]; | |
| filterQueue = dispatch_queue_create("ickBlurFilterQueue", NULL); | |
| }); | |
| }); | |
| if (!art) | |
| return; | |
| if ([UIApplication sharedApplication].applicationState == UIApplicationStateBackground) { | |
| completionHandler(art, nil); | |
| return; | |
| } | |
| dispatch_async(filterQueue, ^{ | |
| CIImage * ciImage = [CIImage imageWithCGImage:art.CGImage]; | |
| CIImage * result; | |
| CGFloat scale = (art.size.width / [self filteredSize]); | |
| CGFloat blurRadius = [self blurRadius]; | |
| CGRect rect = CGRectMake(-(2.0 * blurRadius) * scale, | |
| -(2.0 * blurRadius) * scale, | |
| scale * (4.0 * blurRadius) + art.size.width, | |
| scale * (4.0 * blurRadius) + art.size.height); | |
| UIColor * bgClear = [blendColor colorWithAlphaComponent:1.0]; | |
| CIColor * ciColor = [CIColor colorWithCGColor:bgClear.CGColor]; | |
| if (!ciImage || !bgClear || !ciColor) { | |
| completionHandler(art, nil); | |
| return; | |
| } | |
| [ciColorGenerator setValue:ciColor forKey:@"inputColor"]; | |
| [ciColorControlFilter setValue:@(desaturationFactor) forKey:@"inputSaturation"]; | |
| [ciColorControlFilter setValue:ciImage forKey:kCIInputImageKey]; | |
| blurRadius = blurRadius * scale; | |
| [ciBlurFilter setValue:@(blurRadius) forKey:@"inputRadius"]; | |
| //NSLog(@"Image Size: %f %f, Blur Radius: %f", _coverImage.size.width, _coverImage.size.height, blurRadius); | |
| // the compositor filter combines the generated color background and the desaturated image | |
| [ciCompositor setValue:ciColorGenerator.outputImage forKey:@"inputBackgroundImage"]; | |
| [ciCompositor setValue:ciColorControlFilter.outputImage forKey:@"inputImage"]; | |
| // the blur filter takes the compositor output as input | |
| [ciBlurFilter setValue:ciCompositor.outputImage forKey:kCIInputImageKey]; | |
| result = ciBlurFilter.outputImage; | |
| if (!result) { | |
| completionHandler(art, nil); | |
| return; | |
| } | |
| CGImageRef cgImage = [ciContext createCGImage:result fromRect:rect]; | |
| UIImage * modImage = [UIImage imageWithCGImage:cgImage]; | |
| completionHandler(art, modImage); | |
| CGImageRelease(cgImage); | |
| }); | |
| } |
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