你说的是遮罩吧, BOOL BitBlt( int x, int y, int nWidth, int nHeight, CDC* pSrcDC, int xSrc, int ySrc, DWORD dwRop );dwRopSpecifies the raster operation to be performed. Raster-operation codes define how the GDI combines colors in output operations that involve a current brush, a possible source bitmap, and a destination bitmap. The following lists raster-operation codes for dwRop and their descriptions: BLACKNESS Turns all output black. DSTINVERT Inverts the destination bitmap. MERGECOPY Combines the pattern and the source bitmap using the Boolean AND operator. MERGEPAINT Combines the inverted source bitmap with the destination bitmap using the Boolean OR operator. NOTSRCCOPY Copies the inverted source bitmap to the destination. NOTSRCERASE Inverts the result of combining the destination and source bitmaps using the Boolean OR operator. PATCOPY Copies the pattern to the destination bitmap. PATINVERT Combines the destination bitmap with the pattern using the Boolean XOR operator. PATPAINT Combines the inverted source bitmap with the pattern using the Boolean OR operator. Combines the result of this operation with the destination bitmap using the Boolean OR operator. SRCAND Combines pixels of the destination and source bitmaps using the Boolean AND operator. SRCCOPY Copies the source bitmap to the destination bitmap. SRCERASE Inverts the desination bitmap and combines the result with the source bitmap using the Boolean AND operator. SRCINVERT Combines pixels of the destination and source bitmaps using the Boolean XOR operator. SRCPAINT Combines pixels of the destination and source bitmaps using the Boolean OR operator. WHITENESS Turns all output white.
BOOL BitBlt( int x, int y, int nWidth, int nHeight, CDC* pSrcDC, int xSrc, int ySrc, DWORD dwRop );dwRopSpecifies the raster operation to be performed. Raster-operation codes define how the GDI combines colors in output operations that involve a current brush, a possible source bitmap, and a destination bitmap. The following lists raster-operation codes for dwRop and their descriptions: BLACKNESS Turns all output black.
DSTINVERT Inverts the destination bitmap.
MERGECOPY Combines the pattern and the source bitmap using the Boolean AND operator.
MERGEPAINT Combines the inverted source bitmap with the destination bitmap using the Boolean OR operator.
NOTSRCCOPY Copies the inverted source bitmap to the destination.
NOTSRCERASE Inverts the result of combining the destination and source bitmaps using the Boolean OR operator.
PATCOPY Copies the pattern to the destination bitmap.
PATINVERT Combines the destination bitmap with the pattern using the Boolean XOR operator.
PATPAINT Combines the inverted source bitmap with the pattern using the Boolean OR operator. Combines the result of this operation with the destination bitmap using the Boolean OR operator.
SRCAND Combines pixels of the destination and source bitmaps using the Boolean AND operator.
SRCCOPY Copies the source bitmap to the destination bitmap.
SRCERASE Inverts the desination bitmap and combines the result with the source bitmap using the Boolean AND operator.
SRCINVERT Combines pixels of the destination and source bitmaps using the Boolean XOR operator.
SRCPAINT Combines pixels of the destination and source bitmaps using the Boolean OR operator.
WHITENESS Turns all output white.
pDC->BeginPath();
pDC->Ellipse(0,0,650,300);
pDC->EndPath();
pDC->SelectClipPath(RGN_XOR);
pDC->SelectStockObject(BLACK_BRUSH);
CRect rect;
GetClientRect(&rect);
pDC->Rectangle(&rect);