我很困惑如何做我需要的！任何帮助非常感谢！我有一个透明的图像叠加层,后面有一个UIPanGestureRecognizer和一个UIPinchGestureRecognizer附在其上的另一个图像.顶部的图像有一个完全透明的中间,作为“玻璃”视图.我正在努力将底部的图像从平底锅和夹子中切割成“玻璃”部分. (见下图,看看我在说什么)我已经成功地照顾了平底锅作物,但是当应用捏合时,我正在对其进行正确裁剪.
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！
解决方法
我不知道我是否正确理解你,但这是我的结果：
(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 *theExtraImageView = [UIImageView new];
[thePanImageView addSubview:theExtraImageView];
theExtraImageView.frame = CGRectMake(-thePanImageView.frame.origin.x,-thePanImageView.frame.origin.y,theImageView.frame.size.width,theImageView.frame.size.height);
theExtraImageView.image = theImageView.image;
}
}
- (void)handlePanGesture:(UIPanGestureRecognizer *)thePanGesture
{
UIImageView *thePanImageView = (id)thePanGesture.view;
UIImageView *theImageView = thePanImageView.theWeakObject;
thePanImageView.center = [thePanGesture locationInView:theImageView];
UIImageView *theExtraImageView = thePanImageView.subviews.firstObject;
theExtraImageView.frame = CGRectMake(-thePanImageView.frame.origin.x,theExtraImageView.frame.size.width,theExtraImageView.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 *theExtraImageView = thePanImageView.subviews.firstObject;
theExtraImageView.frame = CGRectMake(-thePanImageView.frame.origin.x,theExtraImageView.frame.size.height);
}
供参考：
