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];

}