Question

让我们假设我们有一个2D空间（以简化情况），以及层S和层C，其中C是S的子层。转换过程必须影响边界，C的位置，C的变换，S的sublayersTransform，C的anchorPoint。我的猜测是下一个：

CGAffineTransform transformToChild(CALayer *S, CALayer *C) {
    CGFloat txa = - C.bounds.origin.x - C.bounds.size.width * C.anchorPoint.x;
    CGFloat tya = - C.bounds.origin.y - C.bounds.size.height * C.anchorPoint.y;

    CGFloat txb = C.position.x;
    CGFloat tyb = C.position.y;

    CGAffineTransform sublayerTransform = CATransform3DGetAffineTransform(S.sublayerTransform);
    CGAffineTransform fromS = CGAffineTransformTranslate(sublayerTransform, txb, tyb);
    fromS = CGAffineTransformConcat(fromS, C.affineTransform);
    fromS = CGAffineTransformTranslate(fromS, txa, tya);

    return fromS;
}

但是当子图层的变换不是标识时（例如，在旋转到M_PI_2角度的情况下），这不起作用。带有图层的整个代码：

CALayer *l1 = [CALayer new];
l1.frame = CGRectMake(-40, -40, 80, 80);
l1.bounds = CGRectMake(40, 40, 80, 80);
CALayer *l2 = [CALayer new];
l2.frame = CGRectMake(50, 40, 20, 20);
l2.bounds = CGRectMake(40, 40, 20, 20);
CGAffineTransform t2 = CGAffineTransformMakeRotation(M_PI / 2);
l2.affineTransform = t2;
[l1 addSublayer:l2];

CGAffineTransform toL2 = transformToChild(l1, l2);
CGPoint p = CGPointApplyAffineTransform(CGPointMake(70, 50), toL2);
NSLog(@"Custom Point %@", [NSValue valueWithCGPoint:p]);

p = [l1 convertPoint:CGPointMake(70, 50) toLayer:l2];
NSLog(@"CoreAnimation Point %@", [NSValue valueWithCGPoint:p]);

与系统结果的比较：

Custom Point NSPoint: {-50, 80}
CoreAnimation Point NSPoint: {50, 40}

Answer 1

这里有一个旧的邮件列表主题，其中包含一些有关此内容的详细信息：

这些消息很旧，所以例如它们不包括几乎最近添加的geometryFlipped属性的效果，但这只会在合并矩阵上添加另一个术语。

Answer 2

所以，我发现了这种与子层坐标空间的点转换方式，它可以与子层的非标识转换一起正常工作。 sublayers这里没有介绍超级层的变换，但我认为扩展这些功能并不难以支持它。

CGPoint pointToChild(CALayer *C, CGPoint p) {

    CGFloat txa = - C.bounds.origin.x - C.bounds.size.width * C.anchorPoint.x;
    CGFloat tya = - C.bounds.origin.y - C.bounds.size.height * C.anchorPoint.y;

    CGFloat txb = C.position.x;
    CGFloat tyb = C.position.y;

    p.x -= txb;
    p.y -= tyb;

    p = CGPointApplyAffineTransform(p, CGAffineTransformInvert(C.affineTransform));

    if (C.isGeometryFlipped) {
        CGAffineTransform flip = CGAffineTransformMakeScale(1.0f, -1.0f);
        flip = CGAffineTransformTranslate(flip, 0, C.bounds.size.height * (2.0f * C.anchorPoint.y - 1.0f));
        p = CGPointApplyAffineTransform(p, CGAffineTransformInvert(flip));
    }

    p.x -= txa;
    p.y -= tya;

    return p;
}

CGPoint pointFromChild(CALayer *C, CGPoint p) {

    CGFloat txb = - C.bounds.origin.x - C.bounds.size.width * C.anchorPoint.x;
    CGFloat tyb = - C.bounds.origin.y - C.bounds.size.height * C.anchorPoint.y;

    CGFloat txa = C.position.x;
    CGFloat tya = C.position.y;

    p.x += txb;
    p.y += tyb;

    if (C.isGeometryFlipped) {
        CGAffineTransform flip = CGAffineTransformMakeScale(1.0f, -1.0f);
        flip = CGAffineTransformTranslate(flip, 0, C.bounds.size.height * (2.0f * C.anchorPoint.y - 1.0f));
        p = CGPointApplyAffineTransform(p, flip);   
    }

    p = CGPointApplyAffineTransform(p, C.affineTransform);

    p.x += txa;
    p.y += tya;

    return p;
}

CALayer如何将点转换为子层？

2 个答案: