iOS 几种背景模糊效果

先上下效果图：
中间的是原图，背景是效果

397E12E0BF9CC8BED8D1AF333DA51503.png

系统的两种方法

1.iOS 7之前系统的类提供UIToolbar来实现毛玻璃效果：

- (void)toolbarStyle{
        let toolRect = CGRect.init(x: 0, y: 0, width: ScreenWidth/2, height: ScreenHeight)
        let toolBar = UIToolbar.init(frame: toolRect)
        toolBar.barStyle = .black
        textImage.addSubview(toolBar)
}

2.iOS 8之后苹果新增加了一个类UIVisualEffectView，通过这个类来实现毛玻璃效果:

/* NS_ENUM_AVAILABLE_IOS(8_0)
     * UIBlurEffectStyleExtraLight,//额外亮度，（高亮风格）
     * UIBlurEffectStyleLight,//亮风格
     * UIBlurEffectStyleDark,//暗风格
     * UIBlurEffectStyleExtraDark __TVOS_AVAILABLE(10_0) __IOS_PROHIBITED __WATCHOS_PROHIBITED,
     * UIBlurEffectStyleRegular NS_ENUM_AVAILABLE_IOS(10_0), // Adapts to user interface style
     * UIBlurEffectStyleProminent NS_ENUM_AVAILABLE_IOS(10_0), // Adapts to user interface style
     */
    lazy var effectView: UIVisualEffectView = {
        let effect = UIBlurEffect.init(style: .light)
        let temp = UIVisualEffectView.init(effect: effect)
        self.topBackView.addSubview(temp)
        return temp
    }()

coreImage

该方法实现的模糊效果较好，模糊程度的可调范围很大，可以根据实际的需求随意调试。缺点就是耗时，我在模拟器上跑需要1-2秒的时间，所有该方法需要放在子线程中执行

dispatch_async(dispatch_get_global_queue(0, 0), ^{
        CIContext *context = [CIContext contextWithOptions:nil];
        CIImage *ciImage = [CIImage imageWithCGImage:image.CGImage];
        CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
        [filter setValue:ciImage forKey:kCIInputImageKey];
        //设置模糊程度
        [filter setValue:@30.0f forKey: @"inputRadius"];
        CIImage *result = [filter valueForKey:kCIOutputImageKey];
        CGRect frame = [ciImage extent];
        NSLog(@"%f,%f,%f,%f",frame.origin.x,frame.origin.y,frame.size.width,frame.size.height);
        CGImageRef outImage = [context createCGImage: result fromRect:ciImage.extent];
        UIImage * blurImage = [UIImage imageWithCGImage:outImage];
        dispatch_async(dispatch_get_main_queue(), ^{
            coreImgv.image = blurImage;
        });
    });

vImage

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

//使用前需要导入头文件
#import <Accelerate/Accelerate.h>
+ (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;
}

源码已经上传至gitHub:
https://github.com/CodeFeel/BlurImage