Do you mean you want to use L_SetBitmapRgnMagicWand? If yes, here's this sample code from our API help file:
L_INT SetBitmapRgnMagicWandExample(pBITMAPHANDLE  pBitmap,
                                                   L_HWND           hWnd,
                                                   L_INT          x,
                                                   L_INT          y)
{
   L_INT nRet;
   RGNXFORM XForm;
   nRet = L_PointToBitmap(pBitmap, TOP_LEFT, &x, &y);
   if(nRet != SUCCESS)
      return nRet;
   if(L_BitmapHasRgn(pBitmap))
      nRet = L_SetBitmapRgnMagicWand(pBitmap, x, y, (20,30,15),(15,30,10), L_RGN_OR);
   else
      nRet = L_SetBitmapRgnMagicWand(pBitmap, x, y, (20,30,15),(15,30,10), L_RGN_SET);
   if(nRet == SUCCESS)
   {
      if(L_BitmapHasRgn(pBitmap))
      {
         HDC hDC=GetDC(hWnd);
         XForm.uViewPerspective=TOP_LEFT;
         XForm.nXScalarNum=1;
         XForm.nXScalarDen=1;
         XForm.nYScalarNum=1;
         XForm.nYScalarDen=1;
         XForm.nXOffset=0;
         XForm.nYOffset=0;
         L_FrameBitmapRgn(hDC, pBitmap, &XForm, 3);
         ReleaseDC(hWnd, hDC);
      }
      else
      {
         MessageBox(hWnd, TEXT("no rgn"), TEXT("error"), MB_OK);
         return nRet;
      }
   }
   return SUCCESS;
}
Please see the help topic "L_SetBitmapRgnMagicWand" for more information.