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. Because the index, not the color value, is inverted, the results are unpredictable.
Inversion works better for direct pixels.
The InvertRgn procedure may move or purge memory blocks in the application heap. Your application should not call this procedure at interrupt time. Inc. All rights reserved.