Lost in Buffered Memory Transfer

[clandestino]

Hi everybody.
I’m working on my own TWAIN Data Source, which should open files from my hard disk and transfers it into any TWAIN-supporting application. Since it took me already some time to get it working, I think I can say I have at least a bare idea of what the TWAIN protocol does. But I don’t know anything on image processing, so I’m using a library called paintlib (you can grab it here http://www.paintlib.de/paintlib/) for the opening and format converting stuff – so lets assume I ony work on Windows Bitmaps. My source works fine on native transfer (DG_IMAGE | DAT_IMAGENATIVEXFER | MSG_GET). The library opens the picture, returns a handle to a copy in global memory, i pass it to the application and thats it.

My problem is the buffered transfer (DG_IMAGE | DAT_IMAGEMEMXFER | MSG_GET), but first things first: I thought, just because my source is only pretending to be a scanner I could return to most of the request dummy data. I provide only mandatory capabilities (mandatory in TWAIN 1.6), the source does not allow to set xy resolution or an image layout, but it returns a layout that more or less fits the layout of the image that is ready to scan.

As long as the application wants to scan native data everything works fine. I only experience problems when the application switches to buffered transfer. Please have a look at these screenshots (See also the code I’m reffering to at the end of this posting):

screenshot from GIMP
These ones are produced by Gimp and Acrobat Reader, and I don’t know where to start fixing the error. I thought passing the memory to the application whould be as straight forward as the native mode. I request enough memory for at least one whole line, max. the entire picture, preferred 10 lines. My code copies the lines from a line array presented by my PAINTLIB library and flips the red and blue color channel if required (this is set in an extern config-file). The scanning process terminates fine but in most cases i recieve these crashed results like shown on the screenshots.

How has experienced the same results during developing a twain source or how knows what i am doing wrong? am i missing something? I don’t get it, please give me some hints. Well, at least thank you very much for reading up to this line. I would appreciate it when you could drop me a line what you think of my problem.

with kind regards,
F.Michels

TW_UINT16 CTW_TransferManager::processMemoryTransfer(TWMSG& msg)

{

CmfctwainApp*	pParent	=NULL;

GET_PARENT(pParent);

ASSERT(pParent != NULL);



pTW_IMAGEMEMXFER	pXfer	=(pTW_IMAGEMEMXFER)msg.pData;

BITMAPINFOHEADER*	pBMIH;



if(pParent->pStatusMgr->getState() == CTW_StatusManager::STATE6)

{

if(pBmp != NULL)

{

pParent->pStatusMgr->setConditionCode(CTW_StatusManager::OPERATIONERROR);

return TWRC_FAILURE;

}

/*

#ifdef _DEBUG

// check what transfer mode we are in

AfxMessageBox("DG_IMAGE | DAT_IMAGEMEMXFER | MSG_GETnImage Buffer Transfer", MB_OK);

#endif

*/

// Bild öffnen

PLAnyPicDecoder		decoder;

//pBmp				=new PLWinBmp;

pDib				=new PLDIBSection;

t_transfer_job		job					=jobQueue.front();	// get current job



#ifdef _DEBUG

decoder.SetTraceConfig(3, NULL);

#endif

//decoder.MakeBmpFromFile(job.strPath, pBmp);



// do we have to switch color channels RGB to BGR ??

iPixelformat	=atoi(pParent->pXmlConfig->getProperty(XMLCFG_PROPERTY_PIXELFORMAT));



// open 32-bit bitmap

decoder.MakeBmpFromFile(job.strPath, pDib);



decoder.Close();



rowCount		=0;



buffer.NewTransfer(pDib);



// Status ändern

pParent->pStatusMgr->setState(CTW_StatusManager::STATE7);

}



// the buffer class takes care of the passed TW_IMAGEMEMXFER structure

// locks memory and fills in the requested fields

buffer.AttachBuffer(pXfer);



BYTE*		pDestRow;

PLPixel32**	lineArray	=pDib->GetLineArray32();



for(int rowIndex=buffer.YOffset(); buffer.GetWriteRowPtr(pDestRow); rowIndex++)

{

PLPixel32*	pSrcRow	=lineArray[rowIndex];

size_t		length	=(pDib->GetBitsPerPixel() * pDib->GetWidth() + 7) / 8;

memcpy(pDestRow, pSrcRow, length);



// flip color channels if required (RGB -> BGR!)

if(iPixelformat	== XMLCFG_PF_BGRx)

{

BYTE*	pbuf	=pDestRow;

for (int n = pDib->GetWidth(); n--; pbuf += 4)

{

BYTE t = pbuf[2];

pbuf[2] = pbuf[0];

pbuf[0] = t;

}

}

}



// unlock memory

buffer.DetachBuffer();



pXfer->Columns	=pXfer->Columns;



if(buffer.XferDone())

{

// clean up

delete pDib;



finishImageTransfer(&jobQueue.front());



return TWRC_XFERDONE;

}

else

return TWRC_SUCCESS;

}

[gabe]

what was the solution?

[clandestino]

set the pixel type wrong (PLANARCHUNKY) and paintlib provided wired samples per pixel (the library reports 3 samples per pixel, but when i copy the memory, every pixel has a forth sample….)

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