在CGPath Scale中获得问题

Question

我使用CGPath绘制多边形并添加到CAShapeLayer。我希望在用户点击它时缩放CGPath。我知道如何扩展CGPath。但是当我点击我的CGPath时，我的CGPath绘图远离中心，而我在中心绘制多边形。

CGAffineTransform scaleTransform = CGAffineTransformMakeScale(scaleFactor, scaleFactor);
CGPathRef oldPath = polygonLayer.path;
CGPathRef scaledPath = CGPathCreateCopyByTransformingPath(oldPath, &scaleTransform);
polygonLayer.path = scaledPath;

Answer 1

问题在于你已经习惯了UIView转换，这是从视图的中心完成的 CGPath转换是在点上完成的（想象CGPointZero作为路径的中心） 我的解决方案：转换为CGPointZero，缩放，然后返回原始坐标。

CGPathRef CGPath_NGCreateCopyByScalingPathAroundCentre(CGPathRef path,
                                           const float scale)
{
    CGRect bounding = CGPathGetPathBoundingBox(path);
    CGPoint pathCenterPoint = CGPointMake(CGRectGetMidX(bounding), CGRectGetMidY(bounding));

    CGAffineTransform translateAndScale = CGAffineTransformTranslate( CGAffineTransformMakeScale(scale, scale), - pathCenterPoint.x, -pathCenterPoint.y) ;
    CGAffineTransform translateBack = CGAffineTransformMakeTranslation(pathCenterPoint.x, pathCenterPoint.y);

    CGPathRef centeredAndScaled = CGPathCreateCopyByTransformingPath(path, &translateAndScale);
    CGPathRef translatedPathRef = CGPathCreateCopyByTransformingPath(centeredAndScaled, &translateBack);

    CGPathRelease(centeredAndScaled);

    return translatedPathRef;
}