objective-c - CoreGraphics 里面的 CGRectApplyAffineTransform 函数 什么作用？

Question

CGRect rect = CGRectMake(0, 0, 300, 200);
        
rect = CGRectApplyAffineTransform(rect,
                                          CGAffineTransformMakeScale(1, -1));
cgPath = CGPathCreateWithRect(rect, NULL);

这段代码什么意思啊？