In This Topic ▼

L_Jp2ExtractFramesBuffer

Summary

Extracts the frames that are specified by puFrames from the input file and save them into a new JPEG 2000 file in a memory buffer that is allocated by the function contains only the extracted frames headers and codestreams directly not through decompressing/compressing process.

Syntax

#include "l_bitmap.h"

L_LTJP2_API L_INT EXT_FUNCTION L_Jp2ExtractFramesBuffer(hJp2, pInFileName, lpBuffer, puBufferSize, puFrames, uNumOfFrames)

Parameters

L_HJP2 hJp2

JPEG 2000 engine handle that was created by the L_Jp2Create function.

L_TCHAR * pInFileName

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

L_UCHAR ** lpBuffer

Pointer to a pointer to be updated with an array of bytes that contains a JPEG 2000 file with extracted frames only. You must free this buffer by calling the Windows GlobalFree() function.

L_SIZE_T * puBufferSize

Address of a variable to be updated with the size of the memory buffer in bytes.

L_UINT32 * puFrames

Array of unsigned integers specifies the indices of the frames to be extracted from the input JPEG 2000 file. All indices shall be 0-based. If any frames index is out the frames number the function will return ERROR_INV_PARAMETER.

L_UINT32 uNumOfFrames

Number of frames to be extracted. This field specifies the size of puFrames array.

Returns

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

Comments

L_Jp2ExtractFramesBuffer extracts the specified frames from the input file and save them into a new JPEG 2000 file in a memory buffer that is allocated by the function contains only the extracted frames headers and codestreams directly not through decompressing/compressing process so it saves processor time and memory. This function is very suitable to server application where multiple clients request specific frames of a JPEG 2000 file so instead of decompressing then compressing the frames this function copies only the needed frames data to generate them and saves the data into a new JPEG 2000 file in a memory buffer.

Required DLLs and Libraries

LTJP2
LTIMGEFX
LFJ2K
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 extracts a frame from JPX file.

L_INT Jp2ExtractFramesBufferExample(L_UINT8** lpOutBuffer, L_SIZE_T * puSize) 
{ 
   L_HJP2 hEngine; 
   L_JP2_FILEINFO Jp2FileInfo; 
   L_UINT32 puFrames[1]; 
   L_INT nRet; 
 
   *lpOutBuffer = NULL; 
   *puSize = 0; 
 
   // Create JPEG  2000 engine handle 
   hEngine = L_Jp2Create(); 
 
   Jp2FileInfo.uStructSize = sizeof(L_JP2_FILEINFO); 
   nRet = L_Jp2GetFileInfo(hEngine, MAKE_IMAGE_PATH("image1.jpx"), &Jp2FileInfo); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   if (Jp2FileInfo.uNumOfFrames < 2) 
      return 0; 
 
   // Extract the second frame 
   puFrames[0] = 1; 
 
   nRet = L_Jp2ExtractFramesBuffer(hEngine, MAKE_IMAGE_PATH("image1.jpx"), lpOutBuffer, puSize, puFrames, 1); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   // Free File Info structure 
   nRet = L_Jp2FreeFileInfo(hEngine, &Jp2FileInfo); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   // Destroy engine handle 
   nRet = L_Jp2Destroy(hEngine); 
   if (nRet != SUCCESS) 
      return nRet; 
 
   return SUCCESS; 
}