对UIBezierPath + applyTransform + CGPath感到困惑

Question

我在x和y方向上按比例2缩放UIBezierPath(由一个[0,0 - 1x1] rect构建).UIBezierPath".bounds"没问题(即按预期缩放),而".CGPath"保持不变......

码:

#import <UIKit/UIKit.h>

int main(int argc, char *argv[])
{
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0,
                                                                     1, 1)];
    NSLog(@"path.bounds box before transform:%@",
          NSStringFromCGRect(path.bounds));
    NSLog(@"path.CGPath box before transform:%@",
          NSStringFromCGRect(CGPathGetBoundingBox(path.CGPath)));

    [path applyTransform:CGAffineTransformMakeScale(2, 2)];

    NSLog(@"path.bounds box after transform:%@",
          NSStringFromCGRect(path.bounds));
    NSLog(@"path.CGPath box after transform:%@",
          NSStringFromCGRect(CGPathGetBoundingBox(path.CGPath)));

    return 0;        
}

输出:

path.bounds box before transform:{{0, 0}, {1, 1}}
path.CGPath box before transform:{{0, 0}, {1, 1}}
path.bounds box after transform:{{0, 0}, {2, 2}}
path.CGPath box after transform:{{0, 0}, {1, 1}}

为什么？

Answer 1

从iOS 5.1开始,当应用了新的转换时,CGPath返回UIBezier的.CGPath属性确实已更新UIBezierPath.

但是,这并不排除旧iOS版本的解决方案.你可以得到CGPath从UIBezierPath直接改造它,然后将其放回UIBezierPath.瞧,所有其他属性,如边界和起源,将立即正确更新.

UIBezierPath* path = [UIBezierPath bezierPathWithRect:CGRectMake(0.0f, 0.0f,
                                                                 1.0f, 1.0f)];

CGAffineTransform transform = CGAffineTransformMakeScale(2.0f, 2.0f);
CGPathRef intermediatePath = CGPathCreateCopyByTransformingPath(path.CGPath,
                                                                &transform);

path.CGPath = intermediatePath;

CGPathRelease(intermediatePath);