How to load/decompress a file into your own buffer

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This topic and its replies were posted before the current version of LEADTOOLS was released and may no longer be applicable.

#1 Posted : Thursday, May 18, 2006 10:29:03 AM(UTC)

Travis

Groups: Registered, Tech Support
Posts: 207

Was thanked: 3 time(s) in 3 post(s)

Attached is an example (written in VC 6.0 using MFC and using LEAD's API functions) that shows how to load an image into a buffer the developer allocates. The bulk of the code is below:

1. When you call L_CreateBitmap, the last parameter must be the EXACT required size.

L_UINT32 GetRequiredSize(L_INT nWidth, L_INT nHeight, L_INT nBitsPerPixel)
{
   L_INT nSize = 0;
   BITMAPHANDLE TempBitmap;
   memset(&TempBitmap, 0, sizeof(TempBitmap));

   nRet = L_InitBitmap(&TempBitmap, sizeof(TempBitmap), nWidth, nHeight, nBitsPerPixel);
   if (nRet == SUCCESS)
   {
      nSize = TempBitmap.Size;
   }
   return nSize;
}

2.
When calling LoadFile, you must pass the flags (LOADFILE_STORE | LOADFILE_NOINITBITMAP) like so:

BOOL MyLoadBitmap(L_CHAR *pszFile, pBITMAPHANDLE pBitmap, L_INT nWidth, L_INT nHeight, L_INT nBitsPerPixel)
{
   L_INT nRet;
   L_INT nSize = 0;
   L_UCHAR *pData = NULL;

   if (!pBitmap)
      return FALSE;

   nSize = GetRequiredSize(nWidth,nHeight,nBitsPerPixel);
   if (nSize == 0)
      return FALSE;

   pData = (L_UCHAR *)malloc(nSize);
   if (!pData)
      return FALSE;

   nRet = L_CreateBitmap(pBitmap, sizeof(BITMAPHANDLE), TYPE_USER, nWidth, nHeight, nBitsPerPixel, ORDER_BGR, 0, BOTTOM_LEFT, pData, nSize);
   if (nRet != SUCCESS)
   {
      free(pData);
      return FALSE;
   }

   nRet = L_LoadFile(pszFile, pBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR,
      LOADFILE_STORE | LOADFILE_NOINITBITMAP, NULL, NULL, NULL, NULL);

   return (nRet == SUCCESS);
}

File Attachment(s):

API - V14 - Load Image into user buffer.zip (89kb) downloaded 59 time(s).

Travis Montgomery
Senior Sales Engineer


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#2 Posted : Wednesday, May 21, 2008 1:19:00 PM(UTC)

DCurtis

Groups: Registered
Posts: 5

That seems to work fine most of the time, but there are cases when it doesn't work. How can I make this code work when there is a different view perspective set in the file that I'm loading?

For example, the attached file has a view perspective of RIGHT_TOP which makes the L_LoadFile call fail. I need to be able to handle this case. What should I do?

File Attachment(s):

ViewPerspective.jpg (3,950kb) downloaded 57 time(s).

#3 Posted : Thursday, May 22, 2008 10:36:17 AM(UTC)

GregR

Groups: Registered, Tech Support, Administrators
Posts: 764

You should set the ELO_IGNOREVIEWPERSPECTIVE flag in the LOADFILEOPTION.Flags property. If you use this for both the call to L_FileInfo and L_LoadFile, then it should work.

Though not necessary for L_LoadFile to return SUCCESS, I would also suggest using the view perspective reported by L_FileInfo as well. Here's the modified code snippet:

void CTutorDlg::OnLoad()
{
    L_INT nRet;
   L_INT nSize = 0;
   L_UCHAR *pData = NULL;
    BITMAPHANDLE Bitmap;
    FILEINFO fi;

    L_INT nWidth, nHeight, nBitsPerPixel, nViewPerspective;

    LOADFILEOPTION lfo;
    L_GetDefaultLoadFileOption(&lfo, sizeof(LOADFILEOPTION));
    lfo.Flags = ELO_IGNOREVIEWPERSPECTIVE;

    nRet = L_FileInfo("Test.jpg", &fi, sizeof(FILEINFO), 0, &lfo);
    nWidth = fi.Width;
    nHeight = fi.Height;
    nBitsPerPixel = fi.BitsPerPixel;
    nViewPerspective = fi.ViewPerspective;

   nSize = GetRequiredSize(nWidth,nHeight,nBitsPerPixel);
   if (nSize == 0)
      return;

   pData = (L_UCHAR *)malloc(nSize);
   if (!pData)
      return;

   nRet = L_CreateBitmap(&Bitmap, sizeof(BITMAPHANDLE), TYPE_USER, nWidth, nHeight, nBitsPerPixel, ORDER_BGR, 0, nViewPerspective, pData, nSize);
   if (nRet != SUCCESS)
   {
      free(pData);
      return;
   }

   nRet = L_LoadFile("Test.jpg", &Bitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR,
      LOADFILE_STORE | LOADFILE_NOINITBITMAP, NULL, NULL, &lfo, NULL);

   return;
}

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