C / C++ / MFC

HANDLE CISImgUtil::DDBToDIB( HBITMAP bitmap, UINT32 dwCompression, HPALETTE hPal ) 
{
	
	CCallbackLock lock;
	
	UINT32                   dwLen;
	HANDLE                  hDIB;
	
	ISASSERT( bitmap );
	
	// The function has no arg for bitfields
	if( dwCompression == BI_BITFIELDS )
	{
		m_error=IS_ERR_INTERNAL;
		return NULL;
	}
	
	// If a palette has not been supplied use default palette
	if (hPal==NULL)
		hPal = (HPALETTE) GetStockObject(DEFAULT_PALETTE);
	
	BITMAP bm;
	// Get bitmap information
	::GetObject(bitmap, sizeof(bm),(LPSTR)&bm);
	
	// Initialize the bitmapinfoheader
	BITMAPINFOHEADER        bi;
	bi.biSize               = sizeof(BITMAPINFOHEADER);
	bi.biWidth              = bm.bmWidth;
	bi.biHeight             = bm.bmHeight;
	bi.biPlanes             = 1;
	bi.biBitCount           = bm.bmPlanes * bm.bmBitsPixel;
	bi.biCompression        = dwCompression;
	bi.biSizeImage          = 0;
	bi.biXPelsPerMeter      = 0;
	bi.biYPelsPerMeter      = 0;
	bi.biClrUsed            = 0;
	bi.biClrImportant       = 0;
	
	// Compute the size of the  infoheader and the color table
	int nColors = (1 << bi.biBitCount);
	
	if( nColors > 256 ) 
		nColors = 0;
	
	if (bi.biBitCount>31)
		nColors=0;
	
	dwLen  = bi.biSize + nColors * sizeof(RGBQUAD);
	
	// We need a device context to get the DIB from
	HDC hDC = GetDC(NULL);
	hPal = SelectPalette(hDC,hPal,FALSE);
	RealizePalette(hDC);
	
	// Allocate enough memory to hold bitmapinfoheader and color table
	hDIB = (HGLOBAL)ISAlloc(dwLen);
	
	if (hDIB==NULL)
	{
		SelectPalette(hDC,hPal,FALSE);
		ReleaseDC(NULL,hDC);
		m_error=IS_ERR_MEM;
		return NULL;
	}
	
	LPBITMAPINFOHEADER lpbi = (LPBITMAPINFOHEADER)hDIB;
	
	*lpbi = bi;
	
	// Call GetDIBits with a NULL lpBits param, so the device driver 
	// will calculate the biSizeImage field 
	if (!GetDIBits(hDC, bitmap, 0L, (UINT32)bi.biHeight,
		(LPBYTE)NULL, (LPBITMAPINFO)lpbi, (UINT32)DIB_RGB_COLORS))
	{
		// error
		ISFree(hDIB);
		
		// Reselect the original palette
		SelectPalette(hDC,hPal,FALSE);
		ReleaseDC(NULL,hDC);
		
		m_error=IS_ERR_GETDIB;
		return NULL;
	}
	
	bi = *lpbi;
	
	// If the driver did not fill in the biSizeImage field, then compute it
	// Each scan line of the image is aligned on a UINT32 (32bit) boundary
	if (bi.biSizeImage == 0){
		bi.biSizeImage = ((((bi.biWidth * bi.biBitCount) + 31) & ~31) / 8) 
			* bi.biHeight;
		
		// If a compression scheme is used the result may infact be larger
		// Increase the size to account for this.
		if (dwCompression != BI_RGB)
			bi.biSizeImage = (bi.biSizeImage * 3) / 2;
	}
	
	// Realloc the buffer so that it can hold all the bits
	dwLen += bi.biSizeImage;
	
	HANDLE hTemp = GlobalReAlloc(hDIB, dwLen, GMEM_MOVEABLE);
	if (hTemp==NULL)
	{
		ISFree(hDIB);
		
		// Reselect the original palette
		SelectPalette(hDC,hPal,FALSE);
		ReleaseDC(NULL,hDC);
		
		m_error=IS_ERR_MEM;
		return NULL;
	}
	
	hDIB=hTemp;
	
	// Get the bitmap bits
	lpbi = (LPBITMAPINFOHEADER)hDIB;
	
	// FINALLY get the DIB
	BOOL bOK = GetDIBits( hDC, bitmap,
		0L,                             // Start scan line
		(UINT32)bi.biHeight,             // # of scan lines
		(LPBYTE)lpbi                    // address for bitmap bits
		+ (bi.biSize + nColors * sizeof(RGBQUAD)),
		(LPBITMAPINFO)lpbi,             // address of bitmapinfo
		(UINT32)DIB_RGB_COLORS);         // Use RGB for color table
	
	if( !bOK )
	{
		ISFree(hDIB);
		
		SelectPalette(hDC,hPal,FALSE);
		ReleaseDC(NULL,hDC);
		m_error=IS_ERR_GETDIB;
		
		return NULL;
	}
	
	SelectPalette(hDC,hPal,FALSE);
	ReleaseDC(NULL,hDC);
	
	return hDIB;
}