ios图片放大缩小

1.设置图片的放大缩小锚点

//两点缩放手势UIPinchGestureRecognizer的响应函数
-(IBAction) pinchGestureHandler:(id)sender
{
    UIPinchGestureRecognizer * pinchGesture = sender;
 
    NSLog(@"缩放手势已经响应");
     
    CGFloat scaleValue = [pinchGesture scale];
 
    imgView.layer.anchorPoint = CGPointMake(0.5,0.5f);
       
    if (scaleValue > 1) {//放大
        pinchGesture.view.transform = CGAffineTransformMakeScale(lastScaleValue+(scaleValue-1), lastScaleValue+(scaleValue-1));
         
    }else{//缩小
        pinchGesture.view.transform = CGAffineTransformMakeScale(lastScaleValue*scaleValue,lastScaleValue*scaleValue);
    }
    if (pinchGesture.state == UIGestureRecognizerStateEnded) {
         
 
        if (scaleValue > 1) {
            lastScaleValue += (scaleValue-1);
        }else{
            lastScaleValue *= scaleValue;
        }
    }
}
//两点缩放手势 安装函数
-(void) installPinchGesture
{
    UIPinchGestureRecognizer * pinchGesture;
     
    //1 构造手势 （注意手势的响应函数）
    pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchGestureHandler:)];
     
    //2 设置手势
    //...
    lastScaleValue = 1;//成员变量
     
    //3 为具体的view添加手势
    [imgView addGestureRecognizer:pinchGesture];
 
}