an example can be found on AMOSPro_Examples:Examples/H-0/Help_9.AMOS
Gives a choice of several alternative GRaphics WRITING modes.
Gr Writing bitpattern
=0, only the graphics set to the current ink colour will be drawn.
=1, new images will completely replace existing images. This is the normal setting.
=1, new images will be combined with existing images.
=1, all new images will be drawn in "inverse video", which means that
the current ink colour will appear as the current paper colour and vice versa.