uiscrollview 图片放大缩小

1、UIScrollView下图片的捏合放大和缩小，我们直接用scrollView自带的属性就可以了，这个没什么好说，我们直接贴代码：
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//控制器  
 theScroll=[[UIScrollView alloc] initWithFrame:frame];  
 theScroll.userInteractionEnabled=YES;  
 theScroll.maximumZoomScale=2.0;//最大倍率（默认倍率）  
 theScroll.minimumZoomScale=1.0;//最小倍率（默认倍率）  
 theScroll.decelerationRate=1.0;//减速倍率（默认倍率）  
 theScroll.delegate=self;  
 theScroll.autoresizingMask =UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleHeight;  
 [self addSubview:theScroll];  
   
 //图片  
 UIImage *theImageName=[UIImage imageNamed:imageName];  
 theImage=[[UIImageView alloc] initWithImage:theImageName];  
 theImage.userInteractionEnabled=YES;  
 theImage.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleHeight;  
 //图片默认作为2倍图处理  
 theImage.frame=CGRectMake(0, 0, theImageName.size.width/2, theImageName.size.height/2);  
 [theScroll addSubview:theImage];  
另外，我们还要在scrollView的delegate里面设置一下：
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#pragma mark -UIScrollView delegate  
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView  
{  
    return theImage;  
}  
2、scrollView对图片的双击放大和缩小
这里我是通过对双击手势（UIGestureRecognizer）和scrollView的setZoomScale方法来实现放大和缩小。
#创建双击手势
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//双击手势  
UITapGestureRecognizer *doubelGesture=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doubleGesture:)];  
doubelGesture.numberOfTapsRequired=2;  
[theImage addGestureRecognizer:doubelGesture];  
[doubelGesture release];  
#另外，我们要记录当前的倍率，然后通过判断，是放大还是缩小。当然，还配合捏合的放大和缩小，所以，要在scrollView的delegate里面记录当前倍率，代码：
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-(void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale  
{  
    currentScale=scale;  
}  

#双击手势的方法
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#pragma mark -DoubleGesture Action  
-(void)doubleGesture:(UIGestureRecognizer *)sender  
{  
      
    //当前倍数等于最大放大倍数  
    //双击默认为缩小到原图  
    if (currentScale==_maxScale) {  
        currentScale=minScale;  
        [theScroll setZoomScale:currentScale animated:YES];  
        return;  
    }  
    //当前等于最小放大倍数  
    //双击默认为放大到最大倍数  
    if (currentScale==minScale) {  
        currentScale=_maxScale;  
        [theScroll setZoomScale:currentScale animated:YES];  
        return;  
    }  
      
    CGFloat aveScale =minScale+(_maxScale-minScale)/2.0;//中间倍数  
      
    //当前倍数大于平均倍数  
    //双击默认为放大最大倍数  
    if (currentScale>=aveScale) {  
        currentScale=_maxScale;  
        [theScroll setZoomScale:currentScale animated:YES];  
        return;  
    }  
      
    //当前倍数小于平均倍数  
    //双击默认为放大到最小倍数  
    if (currentScale<aveScale) {  
        currentScale=minScale;  
        [theScroll setZoomScale:currentScale animated:YES];  
        return;  
    }  
}