#import "ViewController.h"  @interface ViewController () {  UIImageView *_imageView; } @end  @implementation ViewController  - (void)viewDidLoad {  [super viewDidLoad];  _imageView = [[UIImageView alloc]initWithFrame:self.view.bounds];  _imageView.image = [UIImage imageNamed:@"1.jpg"];  [self.view addSubview:_imageView];   //方法一：系統方法，iOS8及以上可用  if (!UIAccessibilityIsReduceTransparencyEnabled()) {  UIBlurEffect *blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleDark];  UIVisualEffectView *blurEffectView = [[UIVisualEffectView alloc]initWithEffect:blurEffect];  blurEffectView.frame = _imageView.bounds;  [_imageView addSubview:blurEffectView];  }    //方法二：Core Image  UIImageView *blurImageView = [[UIImageView alloc]initWithFrame:_imageView.bounds];  blurImageView.image = [self blur:[UIImage imageNamed:@"1.jpg"]];  [_imageView addSubview:blurImageView]; }  //生成一張毛玻璃圖片 - (UIImage*)blur:(UIImage*)theImage {  CIContext *context = [CIContext contextWithOptions:nil];  CIImage *inputImage = [CIImage imageWithCGImage:theImage.CGImage];   CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];  [filter setValue:inputImage forKey:kCIInputImageKey];  [filter setValue:[NSNumber numberWithFloat:15.0f] forKey:@"inputRadius"];  CIImage *result = [filter valueForKey:kCIOutputImageKey];   CGImageRef cgImage = [context createCGImage:result fromRect:[inputImage extent]];   UIImage *returnImage = [UIImage imageWithCGImage:cgImage];  CGImageRelease(cgImage);  return returnImage; }  - (void)didReceiveMemoryWarning {  [super didReceiveMemoryWarning];  // Dispose of any resources that can be recreated. }  @end