ios – 根据UIPinch缩放图像

概述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 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：

weakObject只是我的NSObject的自定义属性.我使用它,因为我很懒惰,不想创建全局可见的@property

总结

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