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LJp2FileFormat::FragmentJpxFile

Summary

Fragments specified codestreams within a JPEG 2000 part 2 JPX file.

Syntax

#include "ltwrappr.h"

L_INT LJp2FileFormat::FragmentJpxFile(pInFileName, pOutFileName, pURLs, uNumOfURLs, pFragments, uNumOfFrgm)

Parameters

L_TCHAR * pInFileName

Character string that contains the name of the JPEG 2000 part 2 JPX file to extract frames from it.

L_TCHAR * pOutFileName

Character string that contains the name of the fragmented JPEG 2000 part 2 JPX file.

pL_JP2_UUID_URL_BOX pURLs

Array of UUID URL boxes specify the file in which the fragments are contained.

L_UINT32 uNumOfURLs

Number of URL boxes, this value specifies the size of the pURLs.

pL_JP2_FRAGMENT pFragments

Pointer to an array of fragments specify for each fragment: the codestream index to be fragmented, the index of URL in which fragment is contained, and the offset of the first byte of the fragment within the URL specified.

L_UINT32 uNumOfFrgm

Size of pFragments.

Returns

Value	Meaning
SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

If a JPX file already has fragments, the function returns: ERROR_INV_PARAMETER.

If the file is not in JPX format the function returns: ERROR_FILE_FORMAT.

You must save the specified codestreams in the URLs provided in pURLs. The codestream must be saved entirely in that URL.

Fragmentation in JPX works by specifying a table of pointers to the individual fragments. Each pointer specifies three things:

The file in which the fragment is contained. Because multiple fragments across multiple codestreams may be stored in the same file, the format encapsulates all filename/URL data into a table (the Data Reference box). Each fragment specification then references an entry in the data reference table.
The offset of the first byte of the fragment within the file specified. This offset is with respect to the first byte of the file (byte 0) and points directly to the first byte of codestream data for the fragment; it does not point to the start of a box containing that fragment.
The length of the fragment, in bytes.

Fragmentation is an important feature of the JPX file format since it allows applications to implement such features as:

Edit an image, resaving the changed tiles to the end of the file.
Distribute the image across several disks for faster access.
Distribute the image across the internet, allowing only certain customers access to the high quality or high resolution portions of the codestream.
Reuse of the headers from within a codestream across multiple codestreams (to minimize file overhead when storing similar codestreams within the same JPX file).

Required DLLs and Libraries

LTJP2
LFJ2K
LTIMGEFX
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.

Example

This example fragments a JPX file.

L_INT LJp2FileFormat__FragmentJpxFileExample(L_VOID) 
{ 
   LJp2FileFormat Engine; 
   L_INT nRet = 0; 
   L_JP2_FILEINFO Jp2FileInfo; 
   L_TCHAR pUrlString[] = MAKE_IMAGE_PATH(TEXT("codestream.bin")); 
   L_JP2_UUID_URL_BOX pURL[1]; 
   L_JP2_FRAGMENT pFragment[1]; 
 
   Jp2FileInfo.uStructSize = sizeof(L_JP2_FILEINFO); 
   nRet = Engine.GetFileInfo(MAKE_IMAGE_PATH(TEXT("image1.jpx")),&Jp2FileInfo); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   if(Jp2FileInfo.MPEG7.uNumOfBoxes == 0) 
      return 0; 
 
   if(Jp2FileInfo.CodeStream.uNumOfBoxes < 2) 
      return 0; 
 
   if(Jp2FileInfo.DataRef.uNumOfBoxes) 
      return 0; 
 
   pURL[0].uStructSize = sizeof(L_JP2_UUID_URL_BOX); 
   pURL[0].pFLAG[0] = 0; 
   pURL[0].pFLAG[1] = 0; 
   pURL[0].pFLAG[2] = 0; 
   pURL[0].uVERS    = 0; 
   pURL[0].pLOC = (L_UINT8*)pUrlString; 
   pURL[0].uLOCSize = (lstrlen(pUrlString)+1)*sizeof(L_TCHAR); 
 
   /*Fragment the second codestream*/ 
   pFragment[0].uStructSize = sizeof(L_JP2_FRAGMENT); 
   pFragment[0].uCodeStreamIndex = 1; 
   pFragment[0].uOffset = 0; 
   pFragment[0].uUrlIndex = 0; 
 
   nRet = Engine.FragmentJpxFile(MAKE_IMAGE_PATH(TEXT("image1.jpx")),MAKE_IMAGE_PATH(TEXT("Test.jpx")), pURL,1,pFragment,1); 
   if(nRet != SUCCESS) 
      return nRet; 
 
   /*Free File Info structure*/ 
   Engine.FreeFileInfo( &Jp2FileInfo); 
    
   return SUCCESS; 
}