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。 

[代码] 在视图中创建手势识别器UIGestureRecognizers

01 - (void)viewDidLoad {
02    [super viewDidLoad];
03  
04    UIPinchGestureRecognizer *pinchRecognizer = [[[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scale:)] autorelease];
05    [pinchRecognizer setDelegate:self];
06    [self.view addGestureRecognizer:pinchRecognizer];
07  
08    UIRotationGestureRecognizer *rotationRecognizer = [[[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotate:)] autorelease];
09    [rotationRecognizer setDelegate:self];
10    [self.view addGestureRecognizer:rotationRecognizer];
11  
12    UIPanGestureRecognizer *panRecognizer = [[[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)] autorelease];
13    [panRecognizer setMinimumNumberOfTouches:1];
14    [panRecognizer setMaximumNumberOfTouches:1];
15    [panRecognizer setDelegate:self];
16    [canvas addGestureRecognizer:panRecognizer];
17  
18    UITapGestureRecognizer *tapProfileImageRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)] autorelease];
19    [tapProfileImageRecognizer setNumberOfTapsRequired:1];
20    [tapProfileImageRecognizer setDelegate:self];
21    [canvas addGestureRecognizer:tapProfileImageRecognizer];
22 }
[代码] 下面是响应各手势消息的方法：
01 // 缩放
02 -(void)scale:(id)sender {
03  
04    if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateBegan) {
05      _lastScale = 1.0;
06    }
07  
08    CGFloat scale = 1.0 - (_lastScale - [(UIPinchGestureRecognizer*)sender scale]);
09  
10    CGAffineTransform currentTransform = photoImage.transform;
11    CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);
12  
13    [photoImage setTransform:newTransform];
14  
15    _lastScale = [(UIPinchGestureRecognizer*)sender scale];
16    [self showOverlayWithFrame:photoImage.frame];
17 }
18  
19 // 旋转
20 -(void)rotate:(id)sender {
21  
22    if([(UIRotationGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {
23  
24      _lastRotation = 0.0;
25      return;
26    }
27  
28    CGFloat rotation = 0.0 - (_lastRotation - [(UIRotationGestureRecognizer*)sender rotation]);
29  
30    CGAffineTransform currentTransform = photoImage.transform;
31    CGAffineTransform newTransform = CGAffineTransformRotate(currentTransform,rotation);
32  
33    [photoImage setTransform:newTransform];
34  
35    _lastRotation = [(UIRotationGestureRecognizer*)sender rotation];
36    [self showOverlayWithFrame:photoImage.frame];
37 }
38  
39 // 移动
40 -(void)move:(id)sender {
41  
42  CGPoint translatedPoint = [(UIPanGestureRecognizer*)sender translationInView:canvas];
43  
44  if([(UIPanGestureRecognizer*)sender state] == UIGestureRecognizerStateBegan) {
45    _firstX = [photoImage center].x;
46    _firstY = [photoImage center].y;
47  }
48  
49  translatedPoint = CGPointMake(_firstX+translatedPoint.x, _firstY+translatedPoint.y);
50  
51  [photoImage setCenter:translatedPoint];
52  [self showOverlayWithFrame:photoImage.frame];
53 }