L_TwainGetJPEGCompression

#include "lttwn.h"

L_LTTWN_API L_INT L_TwainGetJPEGCompression(hSession, pTwJpegComp, uFlag)

HTWAINSESSION hSession;	handle to an existing TWAIN session
pTW_JPEGCOMPRESSION pTwJpegComp;	pointer to a structure
L_UINT uFlag;	flags

Gets the current or default JPEG compression settings for the session.

Parameter	Description
hSession	Handle to an existing TWAIN session. This handle is obtained by calling the L_TwainInitSession or L_TwainInitSession2 function.
pTwJpegComp	Pointer to a TW_JPEGCOMPRESSION structure that contains the JPEG compression settings.
uFlag	Flag that indicates which type of JPEG compression values to get. Possible values are:
	Value	Meaning
	LTWAIN_GET_JPEG_COMPRESSION	[0x0001] Get the current JPEG compression settings
	LTWAIN_GET_DEFAULT_JPEG_COMPRESSION	[0x0002] Get the default JPEG compression settings

Returns

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

Comments

This function will get the current or default TWAIN JPEG compression settings, depending on which flag gets passed to the uFlag parameter.

For more information about TW_JPEGCOMPRESSION, refer to the TWAIN 1.9 specification from the site "http://www.twain.org/".

This function must be called after calling the L_TwainStartCapsNeg function and before calling the L_TwainEndCapsNeg function.

Required DLLs and Libraries

LTTWN

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files to be Included with your Application.

Example

L_INT TwainGetJPEGCompressionExample(HTWAINSESSION hSession) 
{ 
   L_INT nRet; 
   nRet = L_TwainStartCapsNeg (hSession); 
   if(nRet != SUCCESS) 
      return nRet; 
   TW_JPEGCOMPRESSION myJPEG; 
   memset(&myJPEG, 0, sizeof(TW_JPEGCOMPRESSION)); 
   nRet = L_TwainGetJPEGCompression(hSession, &myJPEG, LTWAIN_GET_JPEG_COMPRESSION); 
   if (nRet == SUCCESS) 
   { 
      myJPEG.ColorSpace = TWPT_GRAY; 
      myJPEG.SubSampling = 0x10001000; 
      myJPEG.NumComponents = 1; 
      myJPEG.RestartFrequency = 0; 
      myJPEG.QuantMap[0] = 0; 
      memset(&myJPEG.QuantTable[0], 0, sizeof(TW_MEMORY)); 
      myJPEG.HuffmanMap[0] = 0; 
      memset(&myJPEG.HuffmanDC[0], 0, sizeof(TW_MEMORY)); 
      memset(&myJPEG.HuffmanAC[0], 0, sizeof(TW_MEMORY)); 
      nRet = L_TwainSetJPEGCompression (hSession, &myJPEG, LTWAIN_SET_JPEG_COMPRESSION); 
      if (nRet == SUCCESS) 
      { 
         MessageBox(NULL, TEXT("Setting JPEG compression options was successful"), TEXT("Notice!"), MB_OK); 
         return nRet; 
      } 
   } 
   nRet = L_TwainEndCapsNeg(hSession); 
   if(nRet != SUCCESS) 
      return nRet; 
   return SUCCESS; 
}

Help Version 19.0.2017.10.27

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Function References

Functions:	L_TwainSetJPEGCompression, L_TwainInitSession, L_TwainStartCapsNeg
Topics:	Using JPEG compression for a TWAIN source