Question

我使用CGAffineTransform

旋转视图

[view setTransform:newTransform];

应用变换后帧值保持不变但如何找到此帧的“旋转”或变换值？

http://www.informit.com/content/images/art_sadun_affine/elementLinks/sadun_fig02.png

我想要旋转帧边缘的精确坐标，即a，b，c，d点。

Answer 1

要记住的一点是变换会改变坐标系，因此您需要能够在父“视图”和子视图（转换后的视图）之间进行转换。此外，变换保留变换对象的中心，但不保留任何其他坐标。所以你需要根据中心来计算事物。你需要几个助手。（我从Erica Sadun的书“Core iOS Developer's Cookbook”中获得了以下大部分方法。）

我通常在UIView上添加这些作为类别。

为了将孩子的坐标转换为父坐标，您需要以下内容：

// helper to get pre transform frame
-(CGRect)originalFrame {
   CGAffineTransform currentTransform = self.transform;
   self.transform = CGAffineTransformIdentity;
   CGRect originalFrame = self.frame;
   self.transform = currentTransform;

   return originalFrame;
}

// helper to get point offset from center
-(CGPoint)centerOffset:(CGPoint)thePoint {
    return CGPointMake(thePoint.x - self.center.x, thePoint.y - self.center.y);
}
// helper to get point back relative to center
-(CGPoint)pointRelativeToCenter:(CGPoint)thePoint {
  return CGPointMake(thePoint.x + self.center.x, thePoint.y + self.center.y);
}
// helper to get point relative to transformed coords
-(CGPoint)newPointInView:(CGPoint)thePoint {
    // get offset from center
    CGPoint offset = [self centerOffset:thePoint];
    // get transformed point
    CGPoint transformedPoint = CGPointApplyAffineTransform(offset, self.transform);
    // make relative to center
    return [self pointRelativeToCenter:transformedPoint];
}

// now get your corners
-(CGPoint)newTopLeft {
    CGRect frame = [self originalFrame];
    return [self newPointInView:frame.origin];
}
-(CGPoint)newTopRight {
    CGRect frame = [self originalFrame];
    CGPoint point = frame.origin;
    point.x += frame.size.width;
    return [self newPointInView:point];
}
-(CGPoint)newBottomLeft {
    CGRect frame = [self originalFrame];
    CGPoint point = frame.origin;
    point.y += frame.size.height;
    return [self newPointInView:point];
}
-(CGPoint)newBottomRight {
    CGRect frame = [self originalFrame];
    CGPoint point = frame.origin;
    point.x += frame.size.width;
    point.y += frame.size.height;
    return [self newPointInView:point];
}

Swift 4

extension UIView {
    /// Helper to get pre transform frame
    var originalFrame: CGRect {
        let currentTransform = transform
        transform = .identity
        let originalFrame = frame
        transform = currentTransform
        return originalFrame
    }

    /// Helper to get point offset from center
    func centerOffset(_ point: CGPoint) -> CGPoint {
        return CGPoint(x: point.x - center.x, y: point.y - center.y)
    }

    /// Helper to get point back relative to center
    func pointRelativeToCenter(_ point: CGPoint) -> CGPoint {
        return CGPoint(x: point.x + center.x, y: point.y + center.y)
    }

    /// Helper to get point relative to transformed coords
    func newPointInView(_ point: CGPoint) -> CGPoint {
        // get offset from center
        let offset = centerOffset(point)
        // get transformed point
        let transformedPoint = offset.applying(transform)
        // make relative to center
        return pointRelativeToCenter(transformedPoint)
    }

    var newTopLeft: CGPoint {
        return newPointInView(originalFrame.origin)
    }

    var newTopRight: CGPoint {
        var point = originalFrame.origin
        point.x += originalFrame.width
        return newPointInView(point)
    }

    var newBottomLeft: CGPoint {
        var point = originalFrame.origin
        point.y += originalFrame.height
        return newPointInView(point)
    }

    var newBottomRight: CGPoint {
        var point = originalFrame.origin
        point.x += originalFrame.width
        point.y += originalFrame.height
        return newPointInView(point)
    }
}

Answer 2

您可以使用基本三角函数找出旋转视图的坐标。以下是如何做到这一点：

enter image description here

第一步是了解视图的宽度和高度。将它们除以2，得到三角形的相邻和相对边（分别为青色和绿色）。在上面的示例中，width = 300，height = 300.所以adjacentSide = 150而oppositeSice = 150。
找到斜边（红色）。为此，您使用公式：h^2 = a^2 + b^2。应用此公式后，我们找到了hypotenuse = 212.13
找到theta。这是相邻边（青色）和斜边（红色）之间的角度。为此，您使用公式cos(theta) = (h^2 + a^2 - o^2)/2*h*o。应用该公式后，我们发现θ= 0.785（RADIANS）。要将其转换为度数，我们应用公式degrees = radians * 180 / PI = 45（度）。这是斜边的初始（偏移）角度。这一点非常重要。如果你的观点是旋转的观点是零的，那么它的偏差是45（DEGREES）。我们很快就会需要theta。
现在我们知道了斜边（红色），我们需要rotationAngle。在此示例中，我使用UIRotationGestureRecognizer旋转方形视图。这个类有一个“旋转”属性，告诉我们视图旋转了多少。此值在RADIANS中。在上面的例子中，旋转是0.3597 RADIANS。要将其转换为度数，我们使用公式degrees = radians * PI / 180。应用公式后，我们发现旋转角度为20.61度。
我们终于可以找到偏移宽度（橙色）和高度（紫色）。对于宽度，我们使用公式width = cos(rotationAngle - theta) * hypotenuse，对于高度，我们使用公式height = sen(rotationAngle - theta)。我们必须从旋转角度（在RADIANS TOO中）减去THETA（在RADIANS！中），因为它是初始偏移量。以这种方式查看：当旋转角度为零时，斜边的角度为45（度）。应用公式后，我们发现width = 193.20和height = -87.60
最后，我们可以将这些值（宽度和高度）添加到方形的中心，以找到蓝点的坐标。

- 实施例 -

// Get the center point
CGPoint squareCenter = self.squareView.center;

// Get the blue point coordinates
CGPoint bluePointCoordinates = CGPointMake(squareCenter.x + width, squareCenter.y + height);

蓝点坐标为（963.20,272.40）

为了更好地理解公式，请参阅以下链接：

另外，如果您想要使用我创建的测试项目（图像中的那个），请随时从the following link下载。

<强>更新

这是一个精简方法，可以计算您正在寻找的偏移右上角（蓝色）。

/* Params:
/  viewCenter:      The center point (in superView coordinates) of your view
/  width:           The total width of your view
/  height:          The total height of your view
/  angleOfRotation: The rotation angle of your view. Can be either DEGREES or RADIANS
/  degrees:         A boolean flag indicating whether 'angleOfRotation' is degrees
/                   or radians. E.g.: If 'angleOfRotation' is expressed in degrees
/                   this parameter must be 'YES'
*/
-(CGPoint)calculateTopRightCoordinatesFromViewCenter:(CGPoint)viewCenter viewWidth:(CGFloat)viewWidth viewHeight:(CGFloat)viewHeight angleOfRotation:(CGFloat)angleOfRotation degrees:(BOOL)degrees {

    CGFloat adjacent = viewWidth/2.0;
    CGFloat opposite = viewHeight/2.0;
    CGFloat hipotenuse = sqrtf(powf(adjacent, 2.0) + pow(opposite, 2.0));
    CGFloat thetaRad = acosf((powf(hipotenuse, 2.0) + powf(adjacent, 2.0) - pow(opposite, 2.0)) / (2 * hipotenuse * adjacent));

    CGFloat angleRad = 0.0;
    if (degrees) {
        angleRad = angleOfRotation*M_PI/180.0;
    } else {
        angleRad = angleOfRotation;
    }

    CGFloat widthOffset = cosf(angleRad - thetaRad) * hipotenuse;
    CGFloat heightOffset = sinf(angleRad - thetaRad) * hipotenuse;

    CGPoint offsetPoint = CGPointMake(viewCenter.x + widthOffset, viewCenter.y + heightOffset);
    return offsetPoint;
}

希望这有帮助！

Answer 3

您应该使用：

CGPoint CGPointApplyAffineTransform (
   CGPoint point,
   CGAffineTransform t
);

要获取特定点，请使用视图的边界和中心，然后应用视图的变换以在变换后获得新点。这比专门为旋转变换添加代码更好，因为它可以支持任何变换以及链接。

Answer 4

所有这些答案都很疯狂，这太简单了...

CGPoint topLeft = [rotatedView convertPoint:CGPointMake(0, 0) toView:rotatedView.superview];

CGPoint topRight = [rotatedView convertPoint:CGPointMake(rotatedView.bounds.size.width, 0) toView:rotatedView.superview];

CGPoint bottomLeft = [rotatedView convertPoint:CGPointMake(0, rotatedView.bounds.size.height) toView:rotatedView.superview];

CGPoint bottomRight = [rotatedView convertPoint:CGPointMake(rotatedView.bounds.size.width, rotatedView.bounds.size.height) toView:rotatedView.superview];

Answer 5

试试此代码

CGPoint localBeforeTransform = CGPointMake( view.bounds.size.width/2.0f, view.bounds.size.height/2.0f ); // lower left corner
CGPoint localAfterTransform = CGPointApplyAffineTransform(localBeforeTransform, transform);
CGPoint globalAfterTransform = CGPointMake(localAfterTransform.x + view.center.x, localAfterTransform.y + view.center.y);

Answer 6

为什么乱七八糟？把事情简单化？如果x在变换之前，它将是q rads / degrees，就像锚点周围的每个其他点一样。

将要解释这一切，但是这篇文章中的这一章在更短的背景下解释了它：

Get the current angle/rotation/radian for a UIview?

CGFloat radians = atan2f(yourView.transform.b, yourView.transform.a); 
CGFloat degrees = radians * (180 / M_PI);

Answer 7

我写了这个可以帮助我们的课程：

TransformedViewFrameCalculator.h

#import <Foundation/Foundation.h>

@interface TransformedViewFrameCalculator : NSObject

@property (nonatomic, strong) UIView *viewToProcess;

- (void)calculateTransformedCornersWithTranslation:(CGPoint)translation
                                             scale:(CGFloat)scale
                                          rotation:(CGFloat)rotation;

@property (nonatomic, readonly) CGPoint transformedTopLeftCorner;
@property (nonatomic, readonly) CGPoint transformedTopRightCorner;
@property (nonatomic, readonly) CGPoint transformedBottomLeftCorner;
@property (nonatomic, readonly) CGPoint transformedBottomRightCorner;

@end

TransformedViewFrameCalculator.m：

#import "TransformedViewFrameCalculator.h"

@interface TransformedViewFrameCalculator ()

@property (nonatomic, assign) CGRect viewToProcessNotTransformedFrame;
@property (nonatomic, assign) CGPoint viewToProcessNotTransformedCenter;

@end

@implementation TransformedViewFrameCalculator

- (void)setViewToProcess:(UIView *)viewToProcess {
    _viewToProcess = viewToProcess;

    CGAffineTransform t = _viewToProcess.transform;
    _viewToProcess.transform = CGAffineTransformIdentity;

    _viewToProcessNotTransformedFrame = _viewToProcess.frame;
    _viewToProcessNotTransformedCenter = _viewToProcess.center;

    _viewToProcess.transform = t;
}

- (void)calculateTransformedCornersWithTranslation:(CGPoint)translation
                                             scale:(CGFloat)scale
                                          rotation:(CGFloat)rotation {
    double viewWidth = _viewToProcessNotTransformedFrame.size.width * scale;
    double viewHeight = _viewToProcessNotTransformedFrame.size.height * scale;
    CGPoint viewCenter = CGPointMake(_viewToProcessNotTransformedCenter.x + translation.x,
                                     _viewToProcessNotTransformedCenter.y + translation.y);

    _transformedTopLeftCorner = [self calculateCoordinatesForViewPoint:CGPointMake(0, 0)
                                                        fromViewCenter:viewCenter
                                                             viewWidth:viewWidth
                                                            viewHeight:viewHeight
                                                       angleOfRotation:rotation];

    _transformedTopRightCorner = [self calculateCoordinatesForViewPoint:CGPointMake(0, viewHeight)
                                                         fromViewCenter:viewCenter
                                                              viewWidth:viewWidth
                                                             viewHeight:viewHeight
                                                        angleOfRotation:rotation];

    _transformedBottomLeftCorner = [self calculateCoordinatesForViewPoint:CGPointMake(viewWidth, 0)
                                                           fromViewCenter:viewCenter
                                                                viewWidth:viewWidth
                                                               viewHeight:viewHeight
                                                          angleOfRotation:rotation];

    _transformedBottomRightCorner = [self calculateCoordinatesForViewPoint:CGPointMake(viewWidth, viewHeight)
                                                            fromViewCenter:viewCenter
                                                                 viewWidth:viewWidth
                                                                viewHeight:viewHeight
                                                           angleOfRotation:rotation];
}

- (CGPoint)calculateCoordinatesForViewPoint:(CGPoint)viewPoint
                             fromViewCenter:(CGPoint)viewCenter
                                  viewWidth:(CGFloat)viewWidth
                                 viewHeight:(CGFloat)viewHeight
                            angleOfRotation:(CGFloat)angleOfRotation {
    CGPoint centeredViewPoint = CGPointMake(viewPoint.x - viewWidth/2.0, viewPoint.y - viewHeight/2.0);
    CGPoint rotatedCenteredViewPoint = CGPointApplyAffineTransform(centeredViewPoint, CGAffineTransformMakeRotation(angleOfRotation));
    CGPoint rotatedViewPoint = CGPointMake(rotatedCenteredViewPoint.x + viewCenter.x, rotatedCenteredViewPoint.y + viewCenter.y);
    return rotatedViewPoint;
}

例如，我用它来限制贴纸在容器视图中的移动/缩放/旋转，方法如下：

@property (nonatomic, strong) TransformedViewFrameCalculator *transformedFrameCalculator;

...

self.transformedFrameCalculator = [TransformedViewFrameCalculator new];
self.transformedFrameCalculator.viewToProcess = someView;

...

- (BOOL)transformedView:(UIView *)view
        withTranslation:(CGPoint)translation
                  scale:(double)scale
               rotation:(double)rotation
isFullyInsideValidFrame:(CGRect)validFrame {

    [self.transformedFrameCalculator calculateTransformedCornersWithTranslation:translation
                                                                          scale:scale

    BOOL topRightIsInsideValidFrame = CGRectContainsPoint(validFrame, self.transformedFrameCalculator.transformedTopRightCorner);
    BOOL topLeftIsInsideValidFrame = CGRectContainsPoint(validFrame, self.transformedFrameCalculator.transformedTopLeftCorner);
    BOOL bottomRightIsInsideValidFrame = CGRectContainsPoint(validFrame, self.transformedFrameCalculator.transformedBottomRightCorner);
    BOOL bottomLeftIsInsideValidFrame = CGRectContainsPoint(validFrame, self.transformedFrameCalculator.transformedBottomLeftCorner);

    return topRightIsInsideValidFrame && topLeftIsInsideValidFrame && bottomRightIsInsideValidFrame && bottomLeftIsInsideValidFrame;
}

应用UIView变换后查找帧坐标（CGAffineTransform）

7 个答案: