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ios - 基于 UIPinch 缩放图像

转载 作者:技术小花猫 更新时间:2023-10-29 10:27:38 26 4
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我对如何做我需要的事情感到很困惑!非常感谢任何帮助!我有一个透明的图像叠加层,它后面有另一个图像,附有 UIPanGestureRecognizer 和 UIPinchGestureRecognizer。顶部图像有一个完全透明的中间部分,用作“玻璃” View 。我正在尝试根据平移和捏合将底部图像裁剪到“玻璃”部分。 (请参阅下图以了解我在说什么)我已经成功地处理了平底锅裁剪,但是当也应用了捏合时,我在正确地裁剪它时遇到了问题。

我没有使用 snapshotViewAfterScreenUpdates。

这是我目前的代码:

 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, 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 imageView,而 pendantFrame 是我要裁剪到的区域的中间坐标。

提前致谢!

crop image to the area in the middle

最佳答案

我不确定我是否理解正确,但这是我的结果:

(点击视频观看完整版)

Demo CountPages alpha

- (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, 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, YES, [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,因为每次移动 View 时都会截取屏幕截图。

一种更有效的方法是创建一个额外的 UIImageView,然后将它简单地移动到您的 thePanImageView

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, 0, 100, 100);
thePanImageView.center = CGPointMake(theImageView.frame.size.width/2, 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, -thePanImageView.frame.origin.y, 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, -thePanImageView.frame.origin.y, theExtraImageView.frame.size.width, theExtraImageView.frame.size.height);
}

仅供引用:

theWeakObject 只是我对 NSObject 的自定义属性。我用它是因为我很懒,不想创建全局可见的 @property

关于ios - 基于 UIPinch 缩放图像,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35006625/

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