VC＋＋中SetROP2(R2_MASKPEN)和SetROP2(R2_XORPEN)这两个函数是什么意思

This function sets the current foreground mix mode. GDI uses the foreground mix mode to combine pens and interiors of filled objects with the colors already on the screen. The foreground mix mode defines how colors from the brush or pen are combined with the colors in the existing image.

R2_MASKPEN

Pixel is a combination of the colors common to both the pen and the screen.

R2_XORPEN

Pixel is a combination of the colors in the pen and in the screen, but not in both.