使用手势UIGestureRecognizer对图像进行缩放、移动、旋转操作

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];
}