使用手勢UIGestureRecognizer對圖像進行縮放、移動、旋轉操作

iOS提供了拍擊、旋轉、滑動、擠捏等豐富的手勢，因此對圖像的操作就顯得非常友好、簡單。下面代碼展示了使用UIGestureRecognizer對圖像進行縮放 、移動、旋轉操作使用方法。在使用代碼之前，首先建立一個UIView，并在該視圖中增加一個UIImageView視圖，用于展示圖像。那么該UIView就類似圖 像畫板一樣，對圖像的操作都基于此視圖中進行。

在視圖中創建手勢識別器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];

}</pre> 


 下面是響應各手勢消息的方法： 

// 縮放
-(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];

}
// 旋轉
-(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];

}
// 移動
-(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];
}</pre>