高斯模糊图像 - iOS 8 - 网页学习体会

问题描述：

我有一个移动的背景图像，我想模糊它的底部。我会只用photoshop来做，但是由于图像移动，它不会很好。

I have a moving background image and I want to blur the bottom part of it out. I would do it with just photoshop but since the image moves, it wouldn't work very well.

这就是我的意思（看看在图片的底部）：

Here is what I mean (look at the bottom of the image) :

所以基本上就像Dock对iPhone的影响一样。我使用的是iOS 8而不是Swift。

So basically like the effect the dock has on the iPhone. I'm using iOS 8 but not Swift.

答

我根据您的照片做了一个小例子。我的算法如下：

I have done a small example based on the photo you have there. My algorithm is as follows:

从底部提取一部分图像。

应用高斯滤波器

然后，创建一个新的图像上下文，在其上绘制原始图像。

然后，绘制模糊部分将图像精确地放在原始图像上。

从上下文中提取新图像。

Extract a portion of image from bottom.
Apply gaussian filter to it and blur it.
Then, create a new image context, draw original image on it.
Then, draw the blurred portion of the image to place it exactly over the original image.
Extract the new image from the context.

这是这样做的源代码，

 @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

这是截图结果。

高斯模糊图像 - iOS 8

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