iOS开发多线程之队列组——下载合并图片

转载自iOS开发多线程之队列组——下载合并图片

1. 设计思路

要合并两张图片,用Quartz2D的知识,则要先要搞一个空的大图片,然后再把两张小图片画到那张大图片上面

iOS开发多线程之队列组——下载合并图片_第1张图片
图片.png

2. 实现(由一般实现再过度到队列组)

2.1 方法一(先下载第1张图片,然后下载第2张图片,最后合并图片)弊病:由于图片比较耗时,一张一张的下载图片更耗时。

2.1.1 首先创建一个project,然后拖一个imageview

iOS开发多线程之队列组——下载合并图片_第2张图片
图片.png

2.1.2 连线监听imageview

iOS开发多线程之队列组——下载合并图片_第3张图片
图片.png

2.1.3 代码

//  htingViewController.h  
  
#import   
  
@interface htingViewController : UIViewController  
  
@end  

    //  
    //  htingViewController.m  
      
      
    #import "htingViewController.h"  
      
    @interface htingViewController ()  
    @property (weak, nonatomic) IBOutlet UIImageView *imageView;  
    @property (nonatomic, strong) UIImage *image1;  
    @property (nonatomic, strong) UIImage *image2;  
    @end  
      
    @implementation htingViewController  
      
    - (void)viewDidLoad  
    {  
        [super viewDidLoad];  
        // Do any additional setup after loading the view, typically from a nib.  
    }  
      
    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event  
    {  
        // 异步下载  
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{  
            // 1.下载第1张  
            NSURL *url1 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/f2deb48f8c5494ee460de6182ff5e0fe99257e80.jpg"];  
            NSData *data1 = [NSData dataWithContentsOfURL:url1];  
            UIImage *image1 = [UIImage imageWithData:data1];  
              
            // 2.下载第2张  
            NSURL *url2 = [NSURL URLWithString:@"http://su.bdimg.com/static/superplus/img/logo_white_ee663702.png"];  
            NSData *data2 = [NSData dataWithContentsOfURL:url2];  
            UIImage *image2 = [UIImage imageWithData:data2];  
              
            // 3.合并图片  
            // 开启一个位图上下文  
            UIGraphicsBeginImageContextWithOptions(image1.size, NO, 0.0);  
              
            // 绘制第1张图片  
            CGFloat image1W = image1.size.width;  
            CGFloat image1H = image1.size.height;  
            [image1 drawInRect:CGRectMake(0, 0, image1W, image1H)];  
              
            // 绘制第2张图片  
            CGFloat image2W = image2.size.width * 0.5;  
            CGFloat image2H = image2.size.height * 0.5;  
            CGFloat image2Y = image1H - image2H;  
            [image2 drawInRect:CGRectMake(0, image2Y, image2W, image2H)];  
              
            // 得到上下文中的图片  
            UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();  
              
            // 结束上下文  
            UIGraphicsEndImageContext();  
              
            // 4.回到主线程显示图片  
            dispatch_async(dispatch_get_main_queue(), ^{  
                self.imageView.image = fullImage;  
            });  
        });  
    }  
      
      
    @end  


2.1.4 运行结果

iOS开发多线程之队列组——下载合并图片_第4张图片
图片.png

2.2. 方法二(由于上面的设计中下载图片比较耗时,可以同事开启两个线程同事下载两张图片 )弊病:要搞两个额外的属性

    #import   
      
    @interface htingViewController : UIViewController  
      
    @end  
    //  
    //  htingViewController.m  
      
      
    #import "htingViewController.h"  
      
    @interface htingViewController ()  
    @property (weak, nonatomic) IBOutlet UIImageView *imageView;  
    @property (nonatomic, strong) UIImage *image1;  
    @property (nonatomic, strong) UIImage *image2;  
    @end  
      
    @implementation htingViewController  
      
    - (void)viewDidLoad  
    {  
        [super viewDidLoad];  
        // Do any additional setup after loading the view, typically from a nib.  
    }  
      
    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event  
    {  
          
        // 异步下载  
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{  
            // 1.下载第1张  
            NSURL *url1 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/f2deb48f8c5494ee460de6182ff5e0fe99257e80.jpg"];  
            NSData *data1 = [NSData dataWithContentsOfURL:url1];  
            self.image1 = [UIImage imageWithData:data1];  
              
            [self bindImages];  
        });  
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{  
            // 2.下载第2张  
            NSURL *url2 = [NSURL URLWithString:@"http://su.bdimg.com/static/superplus/img/logo_white_ee663702.png"];  
            NSData *data2 = [NSData dataWithContentsOfURL:url2];  
            self.image2 = [UIImage imageWithData:data2];  
              
            [self bindImages];  
        });  
          
    }  
    - (void)bindImages  
    {  
        if (self.image1 == nil || self.image2 == nil) return;  
          
        // 3.合并图片  
        // 开启一个位图上下文  (相当于创建了一个空的图片)  
        // UIGraphicsBeginImageContextWithOptions(<#CGSize size#>(新的图片有多大), <#BOOL opaque#>(NO代表透明,YES代表不透明), <#CGFloat scale#> (缩放比例))  
        UIGraphicsBeginImageContextWithOptions(self.image1.size, NO, 0.0);  
          
        // 绘制第1张图片 (绘制到上面创建的那个位图上下文上面 也就是那张空的图片上面)  
        CGFloat image1W = self.image1.size.width;  
        CGFloat image1H = self.image1.size.height;  
        [self.image1 drawInRect:CGRectMake(0, 0, image1W, image1H)];  
          
        // 绘制第2张图片  
        CGFloat image2W = self.image2.size.width * 0.5;  
        CGFloat image2H = self.image2.size.height * 0.5;  
        CGFloat image2Y = image1H - image2H;  
        //把image2 绘制到后面的那个区域  
        [self.image2 drawInRect:CGRectMake(0, image2Y, image2W, image2H)];  
          
        // 得到上下文中的图片  
        UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();  
          
        // 结束上下文  
        UIGraphicsEndImageContext();  
          
        // 4.回到主线程显示图片  
        dispatch_async(dispatch_get_main_queue(), ^{  
            self.imageView.image = fullImage;  
        });  
    }  
      
    @end  

2.3 方法三 队列组

    #import   
      
    @interface htingViewController : UIViewController  
      
    @end  
    //  
    //  htingViewController.m  
      
      
    #import "htingViewController.h"  
      
    @interface htingViewController ()  
    @property (weak, nonatomic) IBOutlet UIImageView *imageView;  
    //@property (nonatomic, strong) UIImage *image1;  
    //@property (nonatomic, strong) UIImage *image2;  
    @end  
      
    @implementation htingViewController  
      
    - (void)viewDidLoad  
    {  
        [super viewDidLoad];  
        // Do any additional setup after loading the view, typically from a nib.  
    }  
      
    - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event  
    {  
          
        // 1.队列组  
        dispatch_group_t group = dispatch_group_create();  
        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);  
          
        // 2.下载图片1  
        __block UIImage *image1 = nil;  //要加一个 __block因为 block代码默认不能改外面的东西(记住语法即可)  
        dispatch_group_async(group, queue, ^{  
            NSURL *url1 = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/f2deb48f8c5494ee460de6182ff5e0fe99257e80.jpg"];  
            NSData *data1 = [NSData dataWithContentsOfURL:url1];  
            image1 = [UIImage imageWithData:data1];  
        });  
          
        // 3.下载图片2  
        __block UIImage *image2 = nil;  
        dispatch_group_async(group, queue, ^{  
            NSURL *url2 = [NSURL URLWithString:@"http://su.bdimg.com/static/superplus/img/logo_white_ee663702.png"];  
            NSData *data2 = [NSData dataWithContentsOfURL:url2];  
            image2 = [UIImage imageWithData:data2];  
        });  
          
        // 4.合并图片 用Quartz2D的知识,则要先要搞一个空的大图片,然后再把小图片画上去(保证执行完组里面的所有任务之后,再执行notify函数里面的block)  
        //队列组:要把队列组里面的所有任务都执行完后调用dispatch_group_notify(group, queue, ^{ }  
        dispatch_group_notify(group, queue, ^{  
            // 开启一个位图上下文  
            UIGraphicsBeginImageContextWithOptions(image1.size, NO, 0.0);  
              
            // 绘制第1张图片  
            CGFloat image1W = image1.size.width;  
            CGFloat image1H = image1.size.height;  
            [image1 drawInRect:CGRectMake(0, 0, image1W, image1H)];  
              
            // 绘制第2张图片  
            CGFloat image2W = image2.size.width * 0.5;  
            CGFloat image2H = image2.size.height * 0.5;  
            CGFloat image2Y = image1H - image2H;  
            [image2 drawInRect:CGRectMake(0, image2Y, image2W, image2H)];  
              
            // 得到上下文中的图片  
            UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();  
              
            // 结束上下文  
            UIGraphicsEndImageContext();  
              
            // 5.回到主线程显示图片  
            dispatch_async(dispatch_get_main_queue(), ^{  
                self.imageView.image = fullImage;  
            });  
        });  
          
    }  
      
    @end  
iOS开发多线程之队列组——下载合并图片_第5张图片
图片.png

-**

  • 队列组
    不知道是否正确,看到就载过来,供大家参考
iOS开发多线程之队列组——下载合并图片_第6张图片
图片.png
iOS开发多线程之队列组——下载合并图片_第7张图片

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