从图片创建窗口有效区

CreateRegionFromImage.cpp

BYTE* Get24BitPixels(HBITMAP pBitmap, WORD *pwWidth, WORD *pwHeight)
{
	// a bitmap object just to get bitmap width and height
	BITMAP bmpBmp;

	// pointer to original bitmap info
	LPBITMAPINFO pbmiInfo;

	// bitmap info will hold the new 24bit bitmap info
	BITMAPINFO bmiInfo;

	// width and height of the bitmap
	WORD wBmpWidth, wBmpHeight;

	// ---------------------------------------------------------
	// get some info from the bitmap
	// ---------------------------------------------------------
	GetObject(pBitmap, sizeof(bmpBmp),&bmpBmp);
	pbmiInfo   = (LPBITMAPINFO)&bmpBmp;

	// get width and height
	wBmpWidth  = (WORD)pbmiInfo->bmiHeader.biWidth;
	wBmpWidth -= (wBmpWidth%4);                       // width is 4 byte boundary aligned.
	wBmpHeight = (WORD)pbmiInfo->bmiHeader.biHeight;

	// copy to caller width and height parms
	*pwWidth  = wBmpWidth;
	*pwHeight = wBmpHeight;
	// ---------------------------------------------------------

	// allocate width * height * 24bits pixels
	BYTE *pPixels = new BYTE[wBmpWidth*wBmpHeight*3];
	if (!pPixels) return NULL;

	// get user desktop device context to get pixels from
	HDC hDC = GetWindowDC(NULL);

	// fill desired structure
	bmiInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bmiInfo.bmiHeader.biWidth = wBmpWidth;
	bmiInfo.bmiHeader.biHeight = -wBmpHeight;
	bmiInfo.bmiHeader.biPlanes = 1;
	bmiInfo.bmiHeader.biBitCount = 24;
	bmiInfo.bmiHeader.biCompression = BI_RGB;
	bmiInfo.bmiHeader.biSizeImage = wBmpWidth*wBmpHeight*3;
	bmiInfo.bmiHeader.biXPelsPerMeter = 0;
	bmiInfo.bmiHeader.biYPelsPerMeter = 0;
	bmiInfo.bmiHeader.biClrUsed = 0;
	bmiInfo.bmiHeader.biClrImportant = 0;

	// get pixels from the original bitmap converted to 24bits
	int iRes = GetDIBits(hDC,pBitmap,0,wBmpHeight,(LPVOID)pPixels,&bmiInfo,DIB_RGB_COLORS);

	// release the device context
	ReleaseDC(NULL,hDC);

	// if failed, cancel the operation.
	if (!iRes)
	{
		delete pPixels;
		return NULL;
	};

	// return the pixel array
	return pPixels;
}

HRGN RegionbyBitmap(HBITMAP pBitmap,COLORREF clrTransparent=-1 )
{
	BYTE jTranspR = GetRValue(clrTransparent), jTranspG=GetGValue(clrTransparent), jTranspB=GetBValue(clrTransparent);
	// bitmap width and height
	WORD wBmpWidth,wBmpHeight;

	// the final region and a temporary region
	HRGN hRgn, hTmpRgn;

	// 24bit pixels from the bitmap
	BYTE *pPixels = Get24BitPixels(pBitmap, &wBmpWidth, &wBmpHeight);
	if (!pPixels) return NULL;

	// create our working region
	hRgn = CreateRectRgn(0,0,wBmpWidth,wBmpHeight);
	if (!hRgn) { delete pPixels; return NULL; }

	// ---------------------------------------------------------
	// scan the bitmap
	// ---------------------------------------------------------


	DWORD p=0;
	for (WORD y=0; y<wBmpHeight; y++)
	{
		for (WORD x=0; x<wBmpWidth; x++)
		{
			BYTE jRed   = pPixels[p+2];
			BYTE jGreen = pPixels[p+1];
			BYTE jBlue  = pPixels[p+0];

			if ((jRed == jTranspR && jGreen == jTranspG && jBlue == jTranspB))
			{
				// remove transparent color from region
				hTmpRgn = CreateRectRgn(x,y,x+1,y+1);
				CombineRgn(hRgn, hRgn, hTmpRgn, RGN_DIFF);
				DeleteObject(hTmpRgn);


			}

			// next pixel
			p+=3;
		}
	}

	// release pixels
	delete pPixels;

	return hRgn;
}