Question

我想缩放+翻译视图，然后将此转换动画回来。但是CGAffineTransformInvert返回一个不同的转换（无法理解它的逻辑）。

#import <UIKit/UIKit.h>
@interface TestView : UIView {
    UIView *view;
    CGAffineTransform transform;
}
@end


#import "TestView.h"
#import <QuartzCore/QuartzCore.h>
@implementation TestView
- (void)testAnimation:(NSString*)animationID finished:(NSNumber*)finished context:(void*)context {
    CGAffineTransform transformInverted = CGAffineTransformInvert(transform);
    [UIView beginAnimations:@"test2" context:NULL];
    [UIView setAnimationDuration:3.0];
    [UIView setAnimationCurve:UIViewAnimationCurveLinear];
    view.transform = transformInverted;
    [UIView commitAnimations];
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        view = [[UIView alloc] initWithFrame:CGRectMake(150, 150, 100, 100)];
        view.backgroundColor = [UIColor greenColor];
        [self addSubview:view];

        CGAffineTransform transform1 = CGAffineTransformTranslate(view.transform, -150, -150); 
        transform = CGAffineTransformScale(transform1, (float)1/2, (float)1/2); 

        [UIView beginAnimations:@"test1" context:NULL];
        [UIView setAnimationDuration:3.0];
        [UIView setAnimationCurve:UIViewAnimationCurveLinear];
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(testAnimation:finished:context:) ];

        view.transform = transform;

        [UIView commitAnimations];
    }
    return self;
}

Answer 1

CGAffineTransformInvert反转变换矩阵，并返回一个矩阵，乘以CGAffineTransformIdentity中的原始结果。

如果您想反转翻译/比例，您应该自己跟踪它们。

PS。矩阵非常复杂，它们不存储平移/缩放/旋转值，它们由几个值组成，当乘以坐标时会给出平移/缩放/旋转值，因此您不能期望反转矩阵并得到一个矩阵，其平移，缩放和旋转。

您可以阅读有关他们的更多信息here。

编辑回答你的意见：

使用矩阵时，操作顺序很重要，如果旋转然后翻译，结果将与翻译然后旋转时的结果不同。

要反转应用于矩阵的操作，您应该以相反的顺序应用相反的操作，在这种情况下，要反过来：

CGAffineTransform transform1 = CGAffineTransformTranslate(view.transform, x1, x2);
CGAffineTransform transform2 = CGAffineTransformScale(transform1, r1, r2);
CGAffineTransform transform3 = CGAffineTransformRotate(transform2, a);

你需要这样做：

CGAffineTransform reversed3 = CGAffineTransformRotate(transform3, -a);
CGAffineTransform reversed2 = CGAffineTransformScale(reversed3, 1/r1, 1/r2);
CGAffineTransform reversed1 = CGAffineTransformTranslate(reversed2, -x1, -x2);

[view setTransform:reversed1];

如果你之前没有修改过视图的转换，你可以这样做：

[view setTransform:CGAffineTransformIdentity];

零旋转，零平移和1的刻度。

Answer 2

我不确定我理解你要做什么，但是你不应该只是在testAnimation方法中将视图转换回CGAffineTransformIdentity吗？

Answer 3

考虑下面的代码。这里我们有transformTest，然后我们在它上面应用transform3。然后我们应用于transform3的结果逆。最终结果非常接近transformTest（浮点精度更低）。

如果您在代码中执行view.transform = CGAffineTransformConcat(view.transform, transformInverted);，则可以使用。

CGAffineTransform transformStart = CGAffineTransformIdentity;
CGAffineTransform transform1 = CGAffineTransformTranslate(transformStart, 10, 23);
CGAffineTransform transform2 = CGAffineTransformScale(transform1, 2, 10);
CGAffineTransform transform3 = CGAffineTransformRotate(transform2, M_PI_4);

CGAffineTransform invertedTransform = CGAffineTransformInvert(transform3);


// here actual test
NSLog(@"--------------- here actual test ---------------");

CGAffineTransform transformTest = CGAffineTransformMakeTranslation(2, 15);
transformTest = CGAffineTransformRotate(transformTest, M_PI_2);
transformTest = CGAffineTransformScale(transformTest, 19, 0.4);
transformTest = CGAffineTransformTranslate(transformTest, -33, -19);
NSLog(@"transformTest %@", NSStringFromCGAffineTransform(transformTest));

CGAffineTransform transformTestMultiplied = CGAffineTransformConcat(transformTest, transform3);
NSLog(@"transformTestMultiplied %@", NSStringFromCGAffineTransform(transformTestMultiplied));

CGAffineTransform transformTestMultipliedByInverse = CGAffineTransformConcat(transformTestMultiplied, invertedTransform);
NSLog(@"transformTestMultipliedByInverse %@", NSStringFromCGAffineTransform(transformTestMultipliedByInverse));

这一个的输出：

2016-07-19 13:49:22.034 testUIView[45050:69431115] --------------- here actual test ---------------
2016-07-19 13:49:22.034 testUIView[45050:69431115] transformTest [1.1634144591899855e-15, 19, -0.40000000000000002, 2.4492935982947065e-17, 9.5999999999999623, -612]
2016-07-19 13:49:22.034 testUIView[45050:69431115] transformTestMultiplied [-26.870057685088803, 134.35028842544403, -0.56568542494923812, -2.8284271247461898, 889.0751503711158, -4236.611249867763]
2016-07-19 13:49:22.034 testUIView[45050:69431115] transformTestMultipliedByInverse [0, 19, -0.40000000000000002, 0, 9.5999999999999162, -612]

CGAffineTransformInvert不反转视图转换

3 个答案: