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  • iOS开发-图片高斯模糊效果

    http://www.cnblogs.com/xiaofeixiang/p/5129074.html

    iOS开发的时候有的时候需要将图片设置模糊,或者通过点击下拉方法,去除模糊,一切都是为了应用更受用户欢迎,iOS7之后半透明模糊效果得到大范围使用的比较大,现在也可以看到很多应用局部用到了图片模糊效果,关于图片实现高斯模糊效果有三种方式,CoreImage,GPUImage(第三方开源类库)和vImage。GPUImage没怎么用过,本文就讲两种方式Core Image和vImage。

    Core  Image

    开始撸代码之前我们先来看一下实现的效果:

    iOS5.0之后就出现了Core Image的API,Core Image的API被放在CoreImage.framework库中,在iOS和OS X平台上,Core Image都提供了大量的滤镜(Filter),在OS X上有120多种Filter,而在iOS上也有90多。首先我们扩展一下UIImage,添加类方法:

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    +(UIImage *)coreBlurImage:(UIImage *)image
               withBlurNumber:(CGFloat)blur {
        //博客园-FlyElephant
        CIContext *context = [CIContext contextWithOptions:nil];
        CIImage  *inputImage=[CIImage imageWithCGImage:image.CGImage];
        //设置filter
        CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
        [filter setValue:inputImage forKey:kCIInputImageKey];
        [filter setValue:@(blur) forKey: @"inputRadius"];
        //模糊图片
        CIImage *result=[filter valueForKey:kCIOutputImageKey];
        CGImageRef outImage=[context createCGImage:result fromRect:[result extent]];
        UIImage *blurImage=[UIImage imageWithCGImage:outImage];
        CGImageRelease(outImage);
        return blurImage;
    }

    其中过滤的选项设置为高斯模糊:

      

    vImage 方式

    vImage属于Accelerate.Framework,需要导入Accelerate下的Accelerate头文件,Accelerate主要是用来做数字信号处理、图像处理相关的向量、矩阵运算的库。图像可以认为是由向量或者矩阵数据构成的,Accelerate里既然提供了高效的数学运算API,自然就能方便我们对图像做各种各样的处理,模糊算法使用的是vImageBoxConvolve_ARGB8888这个函数。 

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    +(UIImage *)boxblurImage:(UIImage *)image withBlurNumber:(CGFloat)blur {
        if (blur < 0.f || blur > 1.f) {
            blur = 0.5f;
        }
        int boxSize = (int)(blur * 40);
        boxSize = boxSize - (boxSize % 2) + 1;
         
        CGImageRef img = image.CGImage;
         
        vImage_Buffer inBuffer, outBuffer;
        vImage_Error error;
         
        void *pixelBuffer;
        //从CGImage中获取数据
        CGDataProviderRef inProvider = CGImageGetDataProvider(img);
        CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
        //设置从CGImage获取对象的属性
        inBuffer.width = CGImageGetWidth(img);
        inBuffer.height = CGImageGetHeight(img);
        inBuffer.rowBytes = CGImageGetBytesPerRow(img);
         
        inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);
         
        pixelBuffer = malloc(CGImageGetBytesPerRow(img) *
                             CGImageGetHeight(img));
         
        if(pixelBuffer == NULL)
            NSLog(@"No pixelbuffer");
         
        outBuffer.data = pixelBuffer;
        outBuffer.width = CGImageGetWidth(img);
        outBuffer.height = CGImageGetHeight(img);
        outBuffer.rowBytes = CGImageGetBytesPerRow(img);
         
        error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
         
        if (error) {
            NSLog(@"error from convolution %ld", error);
        }
         
        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
        CGContextRef ctx = CGBitmapContextCreate(
                                                 outBuffer.data,
                                                 outBuffer.width,
                                                 outBuffer.height,
                                                 8,
                                                 outBuffer.rowBytes,
                                                 colorSpace,
                                                 kCGImageAlphaNoneSkipLast);
        CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
        UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
         
        //clean up
        CGContextRelease(ctx);
        CGColorSpaceRelease(colorSpace);
         
        free(pixelBuffer);
        CFRelease(inBitmapData);
         
        CGColorSpaceRelease(colorSpace);
        CGImageRelease(imageRef);
         
        return returnImage;
    }

    图片模糊调用:

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    self.imageView=[[UIImageView alloc]initWithFrame:CGRectMake(0, 300, SCREENWIDTH, 100)];
    self.imageView.contentMode=UIViewContentModeScaleAspectFill;
    self.imageView.image=[UIImage boxblurImage:self.image withBlurNumber:0.5];
    self.imageView.clipsToBounds=YES;
    [self.view addSubview:self.imageView];

    关于两种方式的选择的建议

    效果:第一种Core Image设置模糊之后会在周围产生白边,vImage使用不存在任何问题;

    性能:图像模糊处理属于复杂的计算,大部分图片模糊选择的是vImage,性能最佳(没有亲自测试过,有兴趣可以自己测试)

    项目地址:https://github.com/SmallElephant/iOS-UIImageBoxBlur

    参考资料:https://developer.apple.com/library/ios/documentation/GraphicsImaging/Reference/CoreImageFilterReference/index.html#//apple_ref/doc/filter/ci/CIGaussianBlur

     
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  • 原文地址:https://www.cnblogs.com/itlover2013/p/6146127.html
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