SetROP2
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.
int SetROP2( HDC hdc, int fnDrawMode );
 hdc

[in] Handle to the device context.
 fnDrawMode

[in] Specifies the new mix mode. It is one of the following values.
Value Description R2_BLACK
Pixel is always 0.
R2_COPYPEN
Pixel is the pen color.
R2_MASKNOTPEN
Pixel is a combination of the colors common to both the screen and the inverse of the pen.
R2_MASKPEN
Pixel is a combination of the colors common to both the pen and the screen.
R2_MASKPENNOT
Pixel is a combination of the colors common to both the pen and the inverse of the screen.
R2_MERGENOTPEN
Pixel is a combination of the screen color and the inverse of the pen color.
R2_MERGEPEN
Pixel is a combination of the pen color and the screen color.
R2_MERGEPENNOT
Pixel is a combination of the pen color and the inverse of the screen color.
R2_NOP
Pixel remains unchanged.
R2_NOT
Pixel is the inverse of the screen color.
R2_NOTCOPYPEN
Pixel is the inverse of the pen color.
R2_NOTMASKPEN
Pixel is the inverse of the R2_MASKPEN color.
R2_NOTMERGEPEN
Pixel is the inverse of the R2_MERGEPEN color.
R2_NOTXORPEN
Pixel is the inverse of the R2_XORPEN color.
R2_WHITE
Pixel is always 1.
R2_XORPEN
Pixel is a combination of the colors in the pen and in the screen, but not in both.
If the function succeeds, the return value is the previous mix mode.
If the function fails, the return value is zero.
To get extended error information, call GetLastError.
Mix modes define how GDI combines source and destination colors when drawing with the current pen.
The mix modes are binary raster operation codes, representing all possible Boolean functions of two variables, using the binary operations AND, OR, and XOR (exclusive OR), and the unary operation NOT.
The mix mode is for raster devices only; it is not available for vector devices.