To invert the pixels enclosed by a region, use the InvertRgn procedure. The InvertRgn procedure inverts the pixels enclosed by the region whose handle you pass in the rgn parameter.
Every white pixel becomes black and every black pixel becomes white.
This procedure leaves the location of the graphics pen unchanged. The InvertRgn procedure was designed for 1-bit images in basic graphics ports. This procedure operates on color pixels in color graphics ports, but the results are predictable only with 1-bit or direct pixels. The eight colors used in basic QuickDraw are stored in a color table represented by the global variable QDColors . To display those eight basic QuickDraw colors on an indexed device, Color QuickDraw uses the Color Manager to obtain indexes to the colors in the CLUT that best map to the colors in the QDColors color table.