LFile::LoadOffset

#include "ltwrappr.h"

virtual L_INT LFile::LoadOffset(fd, nOffsetBegin, nBytesToLoad, nBitsPerPixel=0, nOrder=ORDER_BGRORGRAY, uFlags=LOADFILE_ALLOCATE|LOADFILE_STORE, pLoadFileOption=NULL, pFileInfo=NULL)

Loads an image from a file letting you specify the location of the image data within the file. This enables you to load an image file that is embedded in another file.

Returns

Comments

This function supports the LFile::LoadFileOffsetCallBack virtual function.

Note: More information is available in the LOADFILEOPTION structure.

Support for 12 and 16-bit grayscale images is only available in the Document/Medical toolkits.

The location of the image is specified as shown in the following simple illustration:

Note: For information on loading and saving large TIFF files faster, refer to Loading and Saving Large TIFF Files.

Note: You should never pass an uninitialized FILEINFO structure to this function.

Required DLLs and Libraries

Platforms

Win32, x64.

See Also

Example

#define MAKE_IMAGE_PATH(pFileName) TEXT("C:\\Users\\Public\\Documents\\LEADTOOLS Images\\")pFileName
class LUserFile : public LFile
{
   public:
      LUserFile ();
      virtual ~LUserFile ();
      virtual L_INT LoadFileOffsetCallBack(pFILEINFO pFileInfo,
      LBitmapBase * pLBitmap,
      LBuffer * pLBuffer,
      L_UINT uFlags,
      L_INT nRow,
      L_INT nLines);
      virtual L_INT SaveFileOffsetCallBack(LBitmapBase * pLBitmap,
             LBuffer * pLBuffer,
             L_UINT uRow,
             L_UINT uLines);
};
LUserFile::LUserFile ()
{
}
LUserFile::~LUserFile ()
{
}
L_INT LUserFile::LoadFileOffsetCallBack(pFILEINFO pFileInfo,
                                       LBitmapBase * pLBitmap,
                                       LBuffer * pLBuffer,
                                       L_UINT uFlags,
                                       L_INT nRow,
                                       L_INT nLines)
{
   UNREFERENCED_PARAMETER(pFileInfo);
   UNREFERENCED_PARAMETER(pLBitmap);
   UNREFERENCED_PARAMETER(pLBuffer);
   UNREFERENCED_PARAMETER(uFlags);
   UNREFERENCED_PARAMETER(nRow);
   UNREFERENCED_PARAMETER(nLines);
   MessageBox(NULL,TEXT("Here the user can set his code for LoadOffset"),
   TEXT("LoadOffset"),MB_OK);
   return SUCCESS ;
}
L_INT LUserFile:: SaveFileOffsetCallBack(LBitmapBase * pLBitmap,
                                         LBuffer * pLBuffer,
                                         L_UINT uRow,
                                         L_UINT uLines)
{
   UNREFERENCED_PARAMETER(pLBitmap);
   UNREFERENCED_PARAMETER(pLBuffer);
   UNREFERENCED_PARAMETER(uRow);
   UNREFERENCED_PARAMETER(uLines);
   MessageBox(NULL,TEXT("Here the user can set his code for SaveOffset"),
   TEXT("SaveOffset"),MB_OK);
   return SUCCESS ;
}
L_INT LFile__LoadOffsetExample(LBitmapBase& LeadBitmap,HWND hWnd)
{
   L_INT nRet; // Return value 
   L_TCHAR szMessage[80]; // Buffer for the MessageBox string
   L_HANDLE OffsetFile; // File handle 
   L_SSIZE_T SizeWritten; // Variable to be updated with the size written 
   LUserFile UserLeadFile ;
   DWORD wWriteBytes;
   UserLeadFile.SetBitmap(&LeadBitmap);
   // Create a file 
   OffsetFile = CreateFile(MAKE_IMAGE_PATH(TEXT("TOFFSET.TST")), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
   // Write some text in the file -- 29 characters and a terminator 
   WriteFile(OffsetFile, TEXT("This is a 29-character string"), 30, &wWriteBytes, NULL);
   // Save the image file with an offset inside the TOFFSET.TST file 
   nRet = UserLeadFile.SaveOffset((L_HFILE)OffsetFile, 30, &SizeWritten, FILE_BMP, 8, 0, SAVEFILE_FIXEDPALETTE, NULL);
   if(nRet != SUCCESS)
      return nRet;
   // Close the file 
   CloseHandle(OffsetFile);
   // Notify the user with a message box 
   if (nRet == SUCCESS)
   {
      MessageBox (hWnd, TEXT("File was saved"), TEXT("Notice"), MB_OK);
   }
   else
   {
      wsprintf (szMessage, TEXT("Error %d saving the file"), nRet);
      MessageBox (hWnd, szMessage, TEXT("Error"), MB_OK);
      return nRet;
   }
   // Free the bitmap 
   LeadBitmap.Free();
   /***** Now load the file we just saved ****/
   /* Open the file and get the file handle **/
   OffsetFile = CreateFile(MAKE_IMAGE_PATH(TEXT("TOFFSET.TST")), GENERIC_ALL, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
   // Load the file with a 30-byte offset
   nRet = UserLeadFile.LoadOffset((L_HFILE) OffsetFile, 30, SizeWritten,
                                  0, ORDER_BGR, LOADFILE_ALLOCATE | LOADFILE_STORE, NULL);
   // Close the file 
   CloseHandle(OffsetFile);
   /* Notify the user with a message box. The BPS in the message confirms
   that it is a new image. */
   if (nRet == SUCCESS)
   {
      wsprintf (szMessage, TEXT("New file loaded at %d BPS"), LeadBitmap.GetBitsPerPixel());
      MessageBox (NULL, szMessage, TEXT("Notice"), MB_OK);
   }
   else
   {
      wsprintf (szMessage, TEXT("Error %d loading the file"), nRet);
      MessageBox (NULL, szMessage, TEXT("Error"), MB_OK);
   }
   return SUCCESS;
}