iOS提供了拍击、旋转、滑动、挤捏等丰富的手势，因此对图像的操作就显得非常友好、简单。下面代码展示了使用UIGestureRecognizer对图像进行缩放 、移动、旋转操作使用方法。在使用代码之前，首先建立一个UIView，并在该视图中增加一个UIImageView视图，用于展示图像。那么该UIView就类似图 像画板一样，对图像的操作都基于此视图中进行。

在视图中创建手势识别器UIGestureRecognizers

- (void)viewDidLoad {      [super viewDidLoad];        UIPinchGestureRecognizer *pinchRecognizer = [[[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scale:)] autorelease];      [pinchRecognizer setDelegate:self];      [self.view addGestureRecognizer:pinchRecognizer];        UIRotationGestureRecognizer *rotationRecognizer = [[[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotate:)] autorelease];      [rotationRecognizer setDelegate:self];      [self.view addGestureRecognizer:rotationRecognizer];        UIPanGestureRecognizer *panRecognizer = [[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)] autorelease];      [panRecognizer setMinimumNumberOfTouches:1];      [panRecognizer setMaximumNumberOfTouches:1];      [panRecognizer setDelegate:self];      [canvas addGestureRecognizer:panRecognizer];        UITapGestureRecognizer *tapProfileImageRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)] autorelease];      [tapProfileImageRecognizer setNumberOfTapsRequired:1];      [tapProfileImageRecognizer setDelegate:self];      [canvas addGestureRecognizer:tapProfileImageRecognizer];  }

下面是响应各手势消息的方法：

// 缩放  -(void)scale:(id)sender {        if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateBegan) {        _lastScale = 1.0;      }        CGFloat scale = 1.0 - (_lastScale - [(UIPinchGestureRecognizer*)sender scale]);        CGAffineTransform currentTransform = photoImage.transform;      CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);        [photoImage setTransform:newTransform];        _lastScale = [(UIPinchGestureRecognizer*)sender scale];      [self showOverlayWithFrame:photoImage.frame];  }    // 旋转  -(void)rotate:(id)sender {        if([(UIRotationGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {          _lastRotation = 0.0;        return;      }        CGFloat rotation = 0.0 - (_lastRotation - [(UIRotationGestureRecognizer*)sender rotation]);        CGAffineTransform currentTransform = photoImage.transform;      CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform,rotation);        [photoImage setTransform:newTransform];        _lastRotation = [(UIRotationGestureRecognizer*)sender rotation];      [self showOverlayWithFrame:photoImage.frame];  }    // 移动  -(void)move:(id)sender {      CGPoint translatedPoint = [(UIPanGestureRecognizer*)sender translationInView:canvas];      if([(UIPanGestureRecognizer*)sender state] == UIGestureRecognizerStateBegan) {      _firstX = [photoImage center].x;      _firstY = [photoImage center].y;    }      translatedPoint = CGPointMake(_firstX+translatedPoint.x, _firstY+translatedPoint.y);      [photoImage setCenter:translatedPoint];    [self showOverlayWithFrame:photoImage.frame];  }