1.實現效果依次如圖：原圖、iOS8效果、Core Image效果、 VImage 效果

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2. 程式碼

#import "ViewController.h"
#import <Accelerate/Accelerate.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"background"]];
    
//  [self iOS8BlurImageImplement];
//  [self coreImageImplement];
    [self vImageImplement];
}

// iOS8 使用系統自帶的處理方式
- (void)iOS8BlurImageImplement {
    UIBlurEffect *beffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
    UIVisualEffectView *view = [[UIVisualEffectView alloc] initWithEffect:beffect];
    view.frame = self.view.bounds;
    [self.view addSubview:view];
}


// 使用CoreImage實現圖片模糊
- (void)coreImageImplement{
    CIContext *context = [CIContext contextWithOptions:nil];
    
    NSError *error = nil;
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"background" ofType:@"png"];
    NSData *imageData = [NSData dataWithContentsOfFile:filePath options:NSDataReadingUncached error:&error];
    
    //NSData *imageData = [NSData dataWithContentsOfFile:@"background.png"];
    CIImage *image = [CIImage imageWithData:imageData];
    CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [filter setValue:image forKey:kCIInputImageKey];
    [filter setValue:@2.0f forKey:@"inputRadius"];
    CIImage *result = [filter valueForKey:kCIOutputImageKey];
    CGImageRef outImage = [context createCGImage:result fromRect:[result extent]];
    UIImage *bluerImage = [UIImage imageWithCGImage:outImage];
    
    UIImageView *imageView = [[UIImageView alloc] initWithImage:bluerImage];
    imageView.frame = self.view.bounds;
    [self.view addSubview:imageView];
}


// 使用vImage API實現圖片模糊
// iOS5.0中新增了vImage API可以使用，它屬於Accelerate.Framework，所以如果你要使用它要在工程中加入這個Framework。模糊演算法使用的是vImageBoxConvolve_ARGB8888這個函式。
- (void)vImageImplement {
    UIImage *image = [UIImage imageNamed:@"background"];
    UIImage *blurImage = [self blurryImage:image withBlurLevel:0.5];
    self.view.backgroundColor = [UIColor colorWithPatternImage:blurImage];
}

- (UIImage *)blurryImage:(UIImage *)image withBlurLevel:(CGFloat)blur {
    if (blur < 0.f || blur > 1.f) {
        blur = 0.5f;
    }
    int boxSize = (int)(blur * 100);
    boxSize = boxSize - (boxSize % 2) + 1;
    
    CGImageRef img = image.CGImage;
    
    vImage_Buffer inBuffer, outBuffer;
    vImage_Error error;
    
    void *pixelBuffer;
    
    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
    
    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;
}

@end