UIImageView圓角，自適應圖片寬高比例,圖片拉伸,縮放比例

 /*
     設置圓角，經過layer中的cornerRadius和masksToBounds便可。
     
     自適應圖片寬高比例。經過UIViewContentModeScaleAspectFit設置，注意這個UIImageView的frame就不是init中的數據了。
     
     一樣的UIImage圖片放入不一樣frame中的UIImageView就能夠實現比例縮放了。只是UIImageView的大小改變了，

     
     */
    UIImage* image = [UIImage imageNamed:@"back2.jpg"];   
    UIImageView* imageView1 = [[[UIImageView alloc] initWithImage:image] autorelease];   
    imageView1.frame = CGRectMake(0, 0, 300, 200);   
    imageView1.center = CGPointMake(150, 200);
    //設置圓角
    imageView1.layer.cornerRadius = 8;  
    imageView1.layer.masksToBounds = YES; 
    
    //自適應圖片寬高比例
    imageView1.contentMode = UIViewContentModeScaleAspectFit;  
    [self.view addSubview:imageView1];  
    
    
    //拉伸圖片
    CGFloat capWidth = image.size.width / 2;  
    CGFloat capHeight = image.size.height / 2;  
    UIImage* stretchableImage = [image stretchableImageWithLeftCapWidth:capWidth topCapHeight:capHeight];
    UIImageView* imageView3 = [[[UIImageView alloc] initWithImage:stretchableImage] autorelease];
    imageView3.frame = CGRectMake(0, 0, 300, 200);   
    imageView3.center = CGPointMake(150, 200);  
    [self.view addSubview:imageView3]; 
    
    //改變frame改變
    UIImageView* imageView4 = [[[UIImageView alloc] initWithImage:image] autorelease];
    imageView4.frame = CGRectMake(0, 0, 300/2, 200/2);   
    imageView4.center = CGPointMake(150, 200);  
    [self.view addSubview:imageView4];