L_LoadMemoryTile

#include "l_bitmap.h"

L_LTFIL_API L_INT L_LoadMemoryTile(pBuffer, pBitmap, uStructSize, nCol, nRow, uWidth, uHeight, nBitsPerPixel, nOrder, uFlags, pfnCallback, pUserData, nBufferSize, pLoadOptions, pFileInfo)

Loads a section of an image file (any format), using a callback function. The section begins at (nCol, nRow) and extends uWidth pixels across and uHeight pixels down.

Parameters

L_UCHAR* pBuffer

Pointer to the file in memory to be loaded.

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle for the loaded data.

L_UINT uStructSize

Size in bytes, of the structure pointed to by pBitmap for versioning. Use sizeof(BITMAPHANDLE).

L_INT nCol

Left column number of tile.

L_INT nRow

Top row number of tile.

L_UINT uWidth

Tile width in pixels.

L_UINT uHeight

Tile height in pixels.

L_INT nBitsPerPixel

Resulting bitmap pixel depth. The following are valid values:

L_INT nOrder

The desired color order. Possible values are:

L_UINT uFlags

Binary flags that determine the behavior of L_LoadMemoryTile. You can specify one or more of the following values:

FILEREADCALLBACK pfnCallback

Optional callback function for additional processing.

If you do not provide a callback function, use NULL as the value of this parameter.

If you do provide a callback function, use the function pointer as the value of this parameter.

The callback function must adhere to the function prototype described in FILEREADCALLBACK Function.

L_VOID* pUserData

Void pointer that you can use to pass one or more additional parameters that the callback function needs.

To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure.

If the additional parameters are not needed, you can pass NULL in this parameter.

L_SSIZE_T nBufferSize

Size of the file in memory (in bytes).

pLOADFILEOPTION pLoadOptions

Pointer to optional extended load options. Pass NULL to use the default load options.

pFILEINFO pFileInfo

Pointer to a FILEINFO structure. This structure may contain file information used in loading an image, or it may be updated with information about the file being loaded.

If nothing is known about the file, pass NULL for this parameter, or declare a variable of type FILEINFO and set the FILEINFO.Flags to 0, then pass the address of the FILEINFO structure in this parameter. In this case, if the address of a FILEINFO structure is passed, the FILEINFO structure will be updated with the results of L_FileInfo.

If only the file type is known, set pFileInfo.Format to the file type and set pFileInfo.Flags to FILEINFO_FORMATVALID. This can also be done if L_FileInfo has been called previously, but values that affect the size of the image loaded have been changed (for example, by calling L_SetPCDResolution or L_SetWMFResolution). In this case the FILEINFO structure pointed to by pFileInfo will be updated with the results of L_FileInfo.

If L_FileInfo has been called prior to calling this function, and no changes have been made to the contents of the structure filled by L_FileInfo, then the address of the filled FILEINFO structure can be passed for this parameter. In this case, the FILEINFO.Flags member should be set to FILEINFO_INFOVALID. The L_FileInfo function will set the FILEINFO.Flags to FILEINFO_INFOVALID. In this case the load will be faster since this function does not have to query the file filters for the file type.

Note: Local variables are not initialized (since they are placed on the stack). So if you have a FILEINFO structure as a local variable, the value of its Flags parameter is undefined, possibly having FILEINFO_INFOVALID or FILEINFO_FORMATVALID set. That is why it is important to initialize FILEINFO.Flags before passing the address of the FILEINFO structure to the function.

Returns

Comments

This function is very similar to L_LoadFileTile, except that it loads the image from a buffer instead of a file.

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

Notes:

• More options are available in the LOADFILEOPTION structure.

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

Required DLLs and Libraries

• LTFIL
• File format DLLs
• For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Win32, x64, Linux.

// read the file into the buffer. The error checking is reduced for clarity 
L_INT ReadFileIntoBuffer(L_UCHAR *pBuffer, L_OFFSET nBufferSize, L_TCHAR *pszFile) 
{ 
   DWORD dwBytesRead; 
   HANDLE hFile = CreateFile(pszFile, GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); 
   if(hFile == INVALID_HANDLE_VALUE) 
      return ERROR_FILENOTFOUND; 
   ReadFile(hFile, pBuffer, (DWORD)nBufferSize, &dwBytesRead, NULL); 
   CloseHandle(hFile); 
   return SUCCESS; 
} 
  
L_INT LoadMemoryTileExample(L_VOID) 
{ 
   L_INT nRet; 
   BITMAPHANDLE Bitmap; 
   FILEINFO FileInfo; 
   L_UCHAR *pBuffer;    /* Pointer to the data in memory       */ 
   TCHAR *pszFileName = MAKE_IMAGE_PATH(TEXT("clean.tif")); 
   memset(&FileInfo, 0, sizeof(FILEINFO)); 
   FileInfo.uStructSize = sizeof(FileInfo); 
   nRet = L_FileInfo(pszFileName, &FileInfo, sizeof(FILEINFO), 0, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
   // allocate a memory buffer large enough to contain the file 
   pBuffer = (L_UCHAR*)malloc((SIZE_T)FileInfo.SizeDisk); 
   if(!pBuffer) 
      return ERROR_NO_MEMORY; 
   nRet = ReadFileIntoBuffer(pBuffer, FileInfo.SizeDisk, pszFileName); 
   if(nRet != SUCCESS) 
   { 
      free(pBuffer); 
      return nRet; 
   } 
   // Load 1/2 from an image (center) 
   nRet = L_LoadMemoryTile(pBuffer, &Bitmap, sizeof(BITMAPHANDLE), FileInfo.Width/4, FileInfo.Height/4, (FileInfo.Width)/2, (FileInfo.Height)/2, 0, ORDER_BGR, LOADFILE_ALLOCATE | LOADFILE_STORE, NULL, NULL, (L_SSIZE_T)FileInfo.SizeDisk, NULL, &FileInfo); 
   if(nRet != SUCCESS) 
   { 
      free(pBuffer); 
      return nRet; 
   } 
   free(pBuffer); // free the memory buffer, as we are done with it 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &Bitmap, FILE_BMP, 24, 0, NULL); 
   if(nRet != SUCCESS) 
      return nRet; 
   if(Bitmap.Flags.Allocated) 
      L_FreeBitmap(&Bitmap); 
   return SUCCESS; 
}