ViewController.h:

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIGestureRecognizerDelegate> {

    float distStart,distEnd,scale;

    UIScrollView *scrollView;

    UIImage *image;

    UIImageView *imageView;

}

@end

 

ViewController.m:

- (void)viewDidLoad

{

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    //

    scrollView = [[UIScrollView alloc]initWithFrame:CGRectMake((self.view.bounds.origin.x), self.view.bounds.origin.y, self.view.bounds.size.width, self.view.bounds.size.height)];

   

    [self.view addSubview:scrollView];

    image = [UIImage imageNamed:@"img.jpg"];

    imageView = [[UIImageView alloc]initWithImage:image];

    scrollView.contentSize = imageView.bounds.size;

    [scrollView addSubview:imageView];

    [scrollView setBackgroundColor:[UIColor blueColor]];

   

    UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc]

                                                

                                                 initWithTarget:self action:@selector(scale:)];

    [pinchRecognizer setDelegate:self];

    [self.view addGestureRecognizer:pinchRecognizer];

    [pinchRecognizer release];

}

-(void)scale:(id)sender {

    UIPinchGestureRecognizer* ges = (UIPinchGestureRecognizer*)sender;

    int touchCount = ges.numberOfTouches;

    if (touchCount == 2) {

        if ([ges state] == UIGestureRecognizerStateBegan) {

            CGPoint p1 = [ges locationOfTouch:0 inView:self.view];

            CGPoint p2 = [ges locationOfTouch:1 inView:self.view];

            distStart = [self distanceFromPointX:p1 distanceToPointY:p2];

        } else if ([ges state] == UIGestureRecognizerStateEnded) {

            CGPoint p1 = [ges locationOfTouch:0 inView:self.view];

            CGPoint p2 = [ges locationOfTouch:1 inView:self.view];

            distEnd = [self distanceFromPointX:p1 distanceToPointY:p2];

           

            scale = distEnd / distStart;

            float newWidth = imageView.bounds.size.width * scale;           

            float newHeight = imageView.bounds.size.height * scale;

            if (newWidth < self.view.bounds.size.width) {

                newWidth = self.view.bounds.size.width;

                newHeight = imageView.bounds.size.height/imageView.bounds.size.width * newWidth;

            }

           

            if (newHeight < self.view.bounds.size.height) {

                newHeight = self.view.bounds.size.height;

                newWidth = imageView.bounds.size.width/imageView.bounds.size.height * newHeight;

            }

            [imageView setFrame:CGRectMake(0, 0, newWidth, newHeight)];

            scrollView.contentSize = imageView.bounds.size;

            [scrollView setFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];

        }       

    }

}

-(float)distanceFromPointX:(CGPoint)start distanceToPointY:(CGPoint)end{   

    float distance;   

    CGFloat xDist = (end.x - start.x);   

    CGFloat yDist = (end.y - start.y);   

    distance = sqrt((xDist * xDist) + (yDist * yDist));   

    return distance;   

}

还有一种实现方式，代码如下：

-(void)scale:(id)sender {

    UIPinchGestureRecognizer* gues = (UIPinchGestureRecognizer*)sender;

    [self.view bringSubviewToFront:[gues view]];

   

    //当手指离开屏幕时,将lastscale设置为1.0

    if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {

        lastScale = 1.0;

        return;

    }

   

    CGFloat scale = 1.0 - (lastScale - [(UIPinchGestureRecognizer*)sender scale]);

    CGAffineTransform currentTransform = [(UIPinchGestureRecognizer*)sender view].transform;

    CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);

   

   

    [[gues view] setTransform:newTransform]; 

   

   

    lastScale = [(UIPinchGestureRecognizer*)sender scale];   

    CGRect bnds = CGRectApplyAffineTransform(gues.view.bounds, newTransform);

    [sv setContentSize:bnds.size];

    [iv setFrame:bnds];   

}