Inverts the pixels enclosed by an oval.

void InvertOval (
    const Rect *r
);

Parameter descriptions

r

The rectangle that defines the oval’s boundary.

DISCUSSION

The InvertOval function inverts the pixels enclosed by an oval just inside the bounding rectangle that you specify in the r parameter. Every white pixel becomes black and every black pixel becomes white. The pen location does not change.

SPECIAL CONSIDERATIONS

The InvertOval function was designed for 1-bit images in basic graphics ports. This function operates on color pixels in color graphics ports, but the results are predictable only with direct devices or 1-bit pixel maps. For indexed pixels, Color QuickDraw performs the inversion on the pixel indexes, which means the results depend entirely on the contents of the CLUT. 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. Inverting a pure green, for example, that has red, green, and blue component values of $0000, $FFFF, and $0000 results in magenta, which has component values of $FFFF, $0000, and $FFFF.

The InvertOval function may move or purge memory blocks in the application heap; do not call this function at interrupt time.

AVAILABILITY

Supported in Carbon. Available in Carbon 1.0.2 and later when running Mac OS 8.1 or later.

© 2000 Apple Computer, Inc. (Last Updated 6/30/2000)