Win32函数TransparentBltU

BOOL TransparentBltU(
	HDC dcDest,			// handle to Dest DC
	int nXOriginDest,	// x-coord of destination upper-left corner
	int nYOriginDest,	// y-coord of destination upper-left corner
	int nWidthDest,		// width of destination rectangle
	int nHeightDest,	// height of destination rectangle
	HDC dcSrc,			// handle to source DC
	int nXOriginSrc,	// x-coord of source upper-left corner
	int nYOriginSrc,	// y-coord of source upper-left corner
	int nWidthSrc,		// width of source rectangle
	int nHeightSrc,		// height of source rectangle
	UINT crTransparent	// color to make transparent
)
{
	if (nWidthDest < 1) return FALSE;
	if (nWidthSrc < 1) return FALSE;
	if (nHeightDest < 1) return FALSE;
	if (nHeightSrc < 1) return FALSE;

	HDC dc = CreateCompatibleDC(NULL);
	HBITMAP bitmap = CreateBitmap(nWidthSrc, nHeightSrc, 1, GetDeviceCaps(dc,
															BITSPIXEL), NULL);

	if (bitmap == NULL)
	{
		DeleteDC(dc);
		return FALSE;
	}

	HBITMAP oldBitmap = (HBITMAP)SelectObject(dc, bitmap);

	if (!BitBlt(dc, 0, 0, nWidthSrc, nHeightSrc, dcSrc, nXOriginSrc,
														nYOriginSrc, SRCCOPY))
	{
		SelectObject(dc, oldBitmap);
		DeleteObject(bitmap);
		DeleteDC(dc);
		return FALSE;
	}

	HDC maskDC = CreateCompatibleDC(NULL);
	HBITMAP maskBitmap = CreateBitmap(nWidthSrc, nHeightSrc, 1, 1, NULL);

	if (maskBitmap == NULL)
	{
		SelectObject(dc, oldBitmap);
		DeleteObject(bitmap);
		DeleteDC(dc);
		DeleteDC(maskDC);
		return FALSE;
	}

	HBITMAP oldMask =  (HBITMAP)SelectObject(maskDC, maskBitmap);

	SetBkColor(maskDC, RGB(0,0,0));
	SetTextColor(maskDC, RGB(255,255,255));
	if (!BitBlt(maskDC, 0,0,nWidthSrc,nHeightSrc,NULL,0,0,BLACKNESS))
	{
		SelectObject(maskDC, oldMask);
		DeleteObject(maskBitmap);
		DeleteDC(maskDC);
		SelectObject(dc, oldBitmap);
		DeleteObject(bitmap);
		DeleteDC(dc);
		return FALSE;
	}

	SetBkColor(dc, crTransparent);
	BitBlt(maskDC, 0,0,nWidthSrc,nHeightSrc,dc,0,0,SRCINVERT);

	SetBkColor(dc, RGB(0,0,0));
	SetTextColor(dc, RGB(255,255,255));
	BitBlt(dc, 0,0,nWidthSrc,nHeightSrc,maskDC,0,0,SRCAND);

	HDC newMaskDC = CreateCompatibleDC(NULL);
	HBITMAP newMask;
	newMask = CreateBitmap(nWidthDest, nHeightDest, 1,
									GetDeviceCaps(newMaskDC, BITSPIXEL), NULL);

	if (newMask == NULL)
	{
		SelectObject(dc, oldBitmap);
		DeleteDC(dc);
		SelectObject(maskDC, oldMask);
		DeleteDC(maskDC);
		DeleteDC(newMaskDC);
		DeleteObject(bitmap);
		DeleteObject(maskBitmap);
		return FALSE;
	}

	SetStretchBltMode(newMaskDC, COLORONCOLOR);
	HBITMAP oldNewMask = (HBITMAP) SelectObject(newMaskDC, newMask);
	StretchBlt(newMaskDC, 0, 0, nWidthDest, nHeightDest, maskDC, 0, 0,
											nWidthSrc, nHeightSrc, SRCCOPY);

	SelectObject(maskDC, oldMask);
	DeleteDC(maskDC);
	DeleteObject(maskBitmap); 

	HDC newImageDC = CreateCompatibleDC(NULL);
	HBITMAP newImage = CreateBitmap(nWidthDest, nHeightDest, 1,
									GetDeviceCaps(newMaskDC, BITSPIXEL), NULL);

	if (newImage == NULL)
	{
		SelectObject(dc, oldBitmap);
		DeleteDC(dc);
		DeleteDC(newMaskDC);
		DeleteObject(bitmap);
		return FALSE;
	}

	HBITMAP oldNewImage = (HBITMAP)SelectObject(newImageDC, newImage);
	StretchBlt(newImageDC, 0, 0, nWidthDest, nHeightDest, dc, 0, 0, nWidthSrc,
														nHeightSrc, SRCCOPY);

	SelectObject(dc, oldBitmap);
	DeleteDC(dc);
	DeleteObject(bitmap);	 

	BitBlt( dcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest,
													newMaskDC, 0, 0, SRCAND);

	BitBlt( dcDest, nXOriginDest, nYOriginDest, nWidthDest, nHeightDest,
												newImageDC, 0, 0, SRCPAINT);

	SelectObject(newImageDC, oldNewImage);
	DeleteDC(newImageDC);
	SelectObject(newMaskDC, oldNewMask);
	DeleteDC(newMaskDC);
	DeleteObject(newImage);
	DeleteObject(newMask);

	return TRUE;
}