应用 UIView 变换后查找帧坐标 (CGAffineTransform)

Question

我用CGAffineTransform 旋转我的视图

[view setTransform:newTransform];

应用变换后帧值保持不变，但我如何找到该帧的“旋转”或变换值？

_{（来源：informit.com）}

我想要旋转框架边缘的精确坐标，即 a、b、c、d 点。

Answer 1

所有这些答案都是疯狂的，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 2

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（变换后的）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。因此，您需要根据中心来计算事物。您将需要几个助手。 （我从 Erica Sadun 的《Core iOS Developer's Cookbook》一书中获得了以下大部分方法。

我通常将这些作为类别添加到 UIView 上。

为了将孩子的坐标转换成父母的坐标，你需要这样的东西：

// 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];
}

斯威夫特 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 3

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，我用它来限制容器视图内贴纸的移动/缩放/旋转，方式如下：

@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;
}

Answer 4

为什么会乱成一团？把事情简单化？ x 在变换之前的位置，它将进一步 q 弧度/度，就像锚点周围的每个其他点一样。

本打算解释这一切，但这篇文章中的这一章用更短的上下文解释了它：

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 5

试试这个代码

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

您可以使用基本三角法找出旋转视图的坐标。以下是你可以做到的：

1. 第一步是了解视图的宽度和高度。将它们除以 2，得到三角形的相邻边和相对边（分别为青色和绿色）。在上面的示例中，宽度 = 300 和高度 = 300。所以相邻边 = 150 和相反边 = 150。

2. 找到斜边（红色）。为此，您使用公式：h^2 = a^2 + b^2。应用这个公式后，我们发现斜边 = 212.13

3. 找到θ。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。应用此公式后，我们发现 theta = 0.785 (RADIANS)。要将其转换为度数，我们应用公式degrees = radians * 180 / PI = 45（度数）。这是斜边的初始（偏移）角度。意识到这一点非常重要。如果视图的视图旋转为零，则斜边的偏移角为 45（度）。我们很快就会需要 theta。

4. 现在我们知道了斜边（红色），我们需要旋转角度。在这个例子中，我使用了UIRotationGestureRecognizer 来旋转方形视图。这个类有一个“旋转”属性，它告诉我们视图旋转了多少。该值以弧度为单位。在上面的示例中，旋转为 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。

5. 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（也以弧度为单位！）中减去 THETA（以弧度为单位！），因为 THETA 是初始偏移量。这样看：当旋转角度为零时，斜边的角度为 45（度）。应用公式后，我们发现宽度 = 193.20 和高度 = -87.60

6. 最后，我们可以将这些值（宽度和高度）添加到正方形的中心以找到蓝点的坐标。

-示例-

// 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，请查看以下链接：

• Trigonometry 1
• Trigonometry 2

另外，如果您想试用我创建的测试项目（就是图片中的那个），请随时从the following link 下载。

更新

这是一种精简的方法，可以计算您正在寻找的右上角偏移点（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;
}

希望这会有所帮助！

Answer 7

你应该使用：

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取新点。这比添加专门用于旋转变换的代码要好，因为它可以支持任何变换以及链接。