模糊效果，使用FXBlurView这个第三方库可以很轻松的实现这一功能。

效果：

下面来看一下实现，ViewController.m

#import "ViewController.h"
#import "FXBlurView.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UIImage *im = [UIImage imageNamed:@"changmen.jpg"];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:im];
    imageView.frame = CGRectMake(0, 0, im.size.width, im.size.height);
    [self.view addSubview:imageView];
    
    FXBlurView *fxView = [[FXBlurView alloc] initWithFrame:CGRectMake(50, 0, 200, 200)];
    fxView.dynamic = NO;
    fxView.blurRadius = 40;
    fxView.tintColor = [UIColor clearColor];
    [self.view addSubview:fxView];
    
    
    
}

代码下载：http://pan.baidu.com/s/1o64w1YE

iOS模糊效果 使用第三方库 FXBlurView