Gaussian Blur over Image - iOS 8
I have a moving background image and I want to blur the bottom of it. I would do it with just photoshop, but since the image is moving, it won't work very well.
Here's what I mean (look at the bottom of the image):
So basically, like the docking effect on the iPhone. I am using iOS 8 but not Swift.
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I made a small example based on the photo you got there. My algorithm looks like this:
- Extract part of the image below.
- Apply a Gaussian filter to it and lubricate it.
- Then create a new image context, draw the original image on it.
- Then paint the blurred part of the image to position it exactly in comparison to the original image.
- Take the new image out of context.
Here is the source code for that,
@implementation ViewController
- (void)viewDidLoad{
[super viewDidLoad];
UIImageView *imageView = [[UIImageView alloc] init];
imageView.frame = self.view.bounds;
[self.view addSubview:imageView];
imageView.contentMode = UIViewContentModeScaleAspectFit;
UIImage *image = [UIImage imageNamed:@"monogram.jpg"];
imageView.image = [self imageWithBlurredImageWithImage: image andBlurInsetFromBottom: 200 withBlurRadius:3];
}
- (UIImage*)imageWithBlurredImageWithImage:(UIImage*)image andBlurInsetFromBottom:(CGFloat)bottom withBlurRadius:(CGFloat)blurRadius{
UIGraphicsBeginImageContext(image.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextScaleCTM(context, 1, -1);
CGContextTranslateCTM(context, 0, -image.size.height);
CGContextDrawImage(context, CGRectMake(0, 0, image.size.width, image.size.height), image.CGImage);
CGContextDrawImage(context, CGRectMake(0, 0, image.size.width, bottom), [self blurImage: image withBottomInset: bottom blurRadius: blurRadius].CGImage);
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
- (UIImage*)blurImage:(UIImage*)image withBottomInset:(CGFloat)inset blurRadius:(CGFloat)radius{
image = [UIImage imageWithCGImage: CGImageCreateWithImageInRect(image.CGImage, CGRectMake(0, image.size.height - inset, image.size.width,inset))];
CIImage *ciImage = [CIImage imageWithCGImage:image.CGImage];
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
[filter setValue:ciImage forKey:kCIInputImageKey];
[filter setValue:@(radius) forKey:kCIInputRadiusKey];
CIImage *outputCIImage = filter.outputImage;
CIContext *context = [CIContext contextWithOptions:nil];
return [UIImage imageWithCGImage: [context createCGImage:outputCIImage fromRect:ciImage.extent]];
}
@end
And here's a screenshot of the result.
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