按钮剪裁函数//不明白什么情况下会出空间不足的情况if ( pRgnData->nCount >= cBlocks * MAXBUF ){

HRGN GdixConButton::CreateRgnFromBitmap(HBITMAP hBmp, COLORREF color)

{

	if (!hBmp) return NULL;



	BITMAP bm;

	GetObject( hBmp, sizeof(BITMAP), &bm );	// get bitmap attributes



	CDC dcBmp;

	CDC *pDC = GetDC();

	if (!pDC) return NULL;

	dcBmp.CreateCompatibleDC(pDC);	//Creates a memory device context for the bitmap

	ReleaseDC(pDC);

	HBITMAP hOldBitmap = (HBITMAP)dcBmp.SelectObject(hBmp);	//selects the bitmap in the device context



	const DWORD RDHDR = sizeof(RGNDATAHEADER);

	const DWORD MAXBUF = 40;		// size of one block in RECTs

									// (i.e. MAXBUF*sizeof(RECT) in bytes)

	LPRECT	pRects;								

	DWORD	cBlocks = 0;			// number of allocated blocks



	INT		i, j;					// current position in mask image

	INT		first = 0;				// left position of current scan line

									// where mask was found

	bool	wasfirst = false;		// set when if mask was found in current scan line

	bool	ismask;					// set when current color is mask color



	// allocate memory for region data

	RGNDATAHEADER* pRgnData = (RGNDATAHEADER*)new BYTE[ RDHDR + ++cBlocks * MAXBUF * sizeof(RECT) ];

	memset( pRgnData, 0, RDHDR + cBlocks * MAXBUF * sizeof(RECT) );

	// fill it by default

	pRgnData->dwSize	= RDHDR;

	pRgnData->iType		= RDH_RECTANGLES;

	pRgnData->nCount	= 0;

	for ( i = 0; i < bm.bmHeight; i++ )

	for ( j = 0; j < bm.bmWidth; j++ ){

		// get color

		ismask=(dcBmp.GetPixel(j,bm.bmHeight-i-1)!=color);

		// place part of scan line as RECT region if transparent color found after mask color or

		// mask color found at the end of mask image

		if (wasfirst && ((ismask && (j==(bm.bmWidth-1)))||(ismask ^ (j<bm.bmWidth)))){

			// get offset to RECT array if RGNDATA buffer

			pRects = (LPRECT)((LPBYTE)pRgnData + RDHDR);

			// save current RECT

			pRects[ pRgnData->nCount++ ] = CRect( first, bm.bmHeight - i - 1, j+(j==(bm.bmWidth-1)), bm.bmHeight - i );

			// if buffer full reallocate it

			if ( pRgnData->nCount >= cBlocks * MAXBUF ){

				LPBYTE pRgnDataNew = new BYTE[ RDHDR + ++cBlocks * MAXBUF * sizeof(RECT) ];

				memcpy( pRgnDataNew, pRgnData, RDHDR + (cBlocks - 1) * MAXBUF * sizeof(RECT) );

				delete pRgnData;

				pRgnData = (RGNDATAHEADER*)pRgnDataNew;

			}

			wasfirst = false;

		} else if ( !wasfirst && ismask ){		// set wasfirst when mask is found

			first = j;

			wasfirst = true;

		}

	}

	dcBmp.SelectObject( hOldBitmap );

	dcBmp.DeleteDC();	//release the bitmap



	HRGN hRgn=CreateRectRgn(0, 0, 0, 0);

	ASSERT( hRgn!=NULL );

	pRects = (LPRECT)((LPBYTE)pRgnData + RDHDR);

	for(i=0;i<(int)pRgnData->nCount;i++)

	{

		HRGN hr=CreateRectRgn(pRects[i].left, pRects[i].top, pRects[i].right, pRects[i].bottom);

		VERIFY(CombineRgn(hRgn, hRgn, hr, RGN_OR)!=ERROR);

		if (hr) DeleteObject(hr);

	}

	ASSERT( hRgn!=NULL );

	delete pRgnData;

	return hRgn;

}