For creating a region:
L_AutoSegmentBitmap
L_SetBitmapRgnBorder
L_SetBitmapRgnColor
L_SetBitmapRgnColorHSVRange
L_SetBitmapRgnColorRGBRange
L_SetBitmapRgnCurve
L_SetBitmapRgnEllipse
L_SetBitmapRgnFromMask
L_SetBitmapRgnHandle
L_SetBitmapRgnMagicWand
L_SetBitmapRgnPolygon
L_SetBitmapRgnRect
L_SetBitmapRgnRoundRect
L_SliceBitmap
L_SetKaufmannRgnBitmap
For working with the current region:
L_BitmapHasRgn
L_ColorBitmapRgn
L_CreateMaskFromBitmapRgn
L_FrameBitmapRgn
L_FreeBitmapRgn
L_GetBitmapClipSegments
L_GetBitmapClipSegmentsMax
L_GetBitmapRgnArea
L_GetBitmapRgnBounds
L_GetBitmapRgnHandle
L_GetRgnContourPoints
L_GetRgnPerimeterLength
L_HolesRemovalBitmapRgn
L_IsPtInBitmapRgn
L_OffsetBitmapRgn
Regions are not supported on Windows CE.
See Also
Implementing Transparency
L_ResizeBitmapRgn