- (void)stroke
Draws a line along the receiver’s path using the current drawing properties.
- (void)fill
Paints the region enclosed by the receiver’s path using the current drawing properties.
This method fills the path using the current fill color and drawing properties. If the path contains any open subpaths, this method implicitly closes them before painting the fill region.
The painted region includes the pixels right up to, but not including, the path line itself.
原文：https://www.cnblogs.com/feng9exe/p/10339015.html