C / C++ / MFC

YTE* 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;
}
</code>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br />
Peter Weyzen<br />
Staff Engineer<br />
Santa Cruz Networks