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我没有使用snapshotViewAfterScreenupdates.
以下是我到目前为止的代码：
UIImage *snapshotImage; /* draw the image of all the views below our view */ UIGraphicsBeginImageContextWithOptions(self.pendantImageView.bounds.size,NO,0); BOOL successfulDrawHierarchy = [self.pendantImageView drawViewHierarchyInRect:self.pendantImageView.bounds afterScreenupdates:YES]; if ( successfulDrawHierarchy ) { snapshotImage = UIGraphicsGetImageFromCurrentImageContext(); } else { NSLog(@"drawViewHierarchyInRect:afterScreenupdates: Failed - there's nothing to draw..."); } UIGraphicsEndImageContext(); UIImage *croppedImage; if ( successfulDrawHierarchy ) { /* calculate the coordinates of the rectangle we'rE interested in within the returned image */ CGRect cropRect = CGRectOffset(pendantFrame,- self.pendantImageView.frame.origin.x,- self.pendantImageView.frame.origin.y); /* draw the cropped section with a clipping region */ UIGraphicsBeginImageContextWithOptions(cropRect.size,YES,0); CGContextRef context = UIGraphicsGetCurrentContext(); CGContextClipToRect(context,CGRectMake(0,cropRect.size.width,cropRect.size.height)); CGRect targetRectangeForCrop = CGRectMake(-cropRect.origin.x,-cropRect.origin.y,snapshotImage.size.width,snapshotImage.size.height); [snapshotImage drawInRect:targetRectangeForCrop]; croppedImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); }
pendantImageView是底部的imageView,pendantFrame是我正在尝试裁剪的区域的中间坐标.
提前致谢！
(点击视频观看完整版)
- (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; UIImageView *theImageView = [UIImageView new]; [self.view addSubview:theImageView]; theImageView.image = [UIImage imagenamed:@"image1.jpg"]; theImageView.frame = self.view.frame; theImageView.userInteractionEnabled = YES; theImageView.alpha = 0.6; UIImageView *thePanImageView = [UIImageView new]; [self.view addSubview:thePanImageView]; thePanImageView.frame = CGRectMake(0,100,100); thePanImageView.center = CGPointMake(theImageView.frame.size.width/2,theImageView.frame.size.height/2); thePanImageView.image = [self screenshotFromRect:thePanImageView.frame fromView:theImageView]; thePanImageView.userInteractionEnabled = YES; thePanImageView.layer.cornerRadius = thePanImageView.frame.size.width/2; thePanImageView.clipsToBounds = YES; thePanImageView.theWeakObject = theImageView; { UIPanGestureRecognizer *thePanGesture = [UIPanGestureRecognizer new]; [thePanGesture addTarget:self action:@SELEctor(handlePanGesture:)]; [thePanImageView addGestureRecognizer:thePanGesture]; UIPinchGestureRecognizer *thePinchGesture = [UIPinchGestureRecognizer new]; [thePinchGesture addTarget:self action:@SELEctor(handlePinchGesture:)]; [thePanImageView addGestureRecognizer:thePinchGesture]; } } - (void)handlePanGesture:(UIPanGestureRecognizer *)thePanGesture { UIImageView *thePanImageView = (id)thePanGesture.view; UIImageView *theImageView = thePanImageView.theWeakObject; thePanImageView.center = [thePanGesture LOCATIOnInView:theImageView]; thePanImageView.image = [self screenshotFromRect:thePanImageView.frame fromView:theImageView]; } - (void)handlePinchGesture:(UIPinchGestureRecognizer *)thePinchGesture { UIImageView *thePanImageView = (id)thePinchGesture.view; static CGRect theInitialFrame; if (thePinchGesture.state == UIGestureRecognizerStateBegan) { theInitialFrame = thePanImageView.frame; } else { CGRect theFrame = theInitialFrame; theFrame.size.width *= thePinchGesture.scale; theFrame.size.height *= thePinchGesture.scale; thePanImageView.frame = theFrame; } thePanImageView.layer.cornerRadius = thePanImageView.frame.size.width/2; UIImageView *theImageView = thePanImageView.theWeakObject; thePanImageView.center = [thePinchGesture LOCATIOnInView:theImageView]; thePanImageView.image = [self screenshotFromRect:thePanImageView.frame fromView:theImageView]; } - (UIImage * __nonnull)screenshotFromRect:(CGRect)theRect fromView:(UIView * __nonnull)theView; { if (!theView) { abort(); } if (theRect.size.height < 1 || theRect.size.width < 1) { abort(); } if ([[UIScreen mainScreen] respondsToSELEctor:@SELEctor(scalE)]) { UIGraphicsBeginImageContextWithOptions(theRect.size,[UIScreen mainScreen].scalE); } else { UIGraphicsBeginImageContext(theRect.sizE); } CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextTranslateCTM(ctx,-theRect.origin.x,-theRect.origin.y); [theView.layer renderInContext:ctx]; UIImage *snapshotImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return snapshotImage; }
编辑：
上述解决方案在cpu方面效率低下,因为它每次移动视图时都需要截图.
一个更有效的方式是创建一个额外的UIImageView,并将其移动到您的PangImageView内
代码如下：
- (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; UIImageView *theImageView = [UIImageView new]; [self.view addSubview:theImageView]; theImageView.image = [UIImage imagenamed:@"image1.jpg"]; theImageView.frame = self.view.frame; theImageView.userInteractionEnabled = YES; theImageView.alpha = 0.6; UIImageView *thePanImageView = [UIImageView new]; [self.view addSubview:thePanImageView]; thePanImageView.frame = CGRectMake(0,theImageView.frame.size.height/2); thePanImageView.userInteractionEnabled = YES; thePanImageView.layer.cornerRadius = thePanImageView.frame.size.width/2; thePanImageView.clipsToBounds = YES; thePanImageView.layer.borderColor = [UIColor redColor].CGColor; thePanImageView.layer.borderWidth = 1; thePanImageView.theWeakObject = theImageView; { UIPanGestureRecognizer *thePanGesture = [UIPanGestureRecognizer new]; [thePanGesture addTarget:self action:@SELEctor(handlePanGesture:)]; [thePanImageView addGestureRecognizer:thePanGesture]; UIPinchGestureRecognizer *thePinchGesture = [UIPinchGestureRecognizer new]; [thePinchGesture addTarget:self action:@SELEctor(handlePinchGesture:)]; [thePanImageView addGestureRecognizer:thePinchGesture]; UIImageView *theExTraiR_245_11845@ageView = [UIImageView new]; [thePanImageView addSubview:theExTraiR_245_11845@ageView]; theExTraiR_245_11845@ageView.frame = CGRectMake(-thePanImageView.frame.origin.x,-thePanImageView.frame.origin.y,theImageView.frame.size.width,theImageView.frame.size.height); theExTraiR_245_11845@ageView.image = theImageView.image; } } - (void)handlePanGesture:(UIPanGestureRecognizer *)thePanGesture { UIImageView *thePanImageView = (id)thePanGesture.view; UIImageView *theImageView = thePanImageView.theWeakObject; thePanImageView.center = [thePanGesture LOCATIOnInView:theImageView]; UIImageView *theExTraiR_245_11845@ageView = thePanImageView.subviews.firstObject; theExTraiR_245_11845@ageView.frame = CGRectMake(-thePanImageView.frame.origin.x,theExTraiR_245_11845@ageView.frame.size.width,theExTraiR_245_11845@ageView.frame.size.height); } - (void)handlePinchGesture:(UIPinchGestureRecognizer *)thePinchGesture { UIImageView *thePanImageView = (id)thePinchGesture.view; static CGRect theInitialFrame; if (thePinchGesture.state == UIGestureRecognizerStateBegan) { theInitialFrame = thePanImageView.frame; } else { CGRect theFrame = theInitialFrame; theFrame.size.width *= thePinchGesture.scale; theFrame.size.height *= thePinchGesture.scale; thePanImageView.frame = theFrame; } thePanImageView.layer.cornerRadius = thePanImageView.frame.size.width/2; UIImageView *theImageView = thePanImageView.theWeakObject; thePanImageView.center = [thePinchGesture LOCATIOnInView:theImageView]; UIImageView *theExTraiR_245_11845@ageView = thePanImageView.subviews.firstObject; theExTraiR_245_11845@ageView.frame = CGRectMake(-thePanImageView.frame.origin.x,theExTraiR_245_11845@ageView.frame.size.height); }
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