Qt4 and TWAIN scanning

Hi,
I'm trying to use Qt4 to scan images using TWAIN on Windows.
I have downloaded Qt TWAIN Package from http://www.cppfrance.com/codes/PACKA...AIN_46374.aspx and I'm modifing it to use Qt 4. The code was created by "Stephan Stapel" using Qt 3.

I've attached the Visual Studio Solution into the zip file to get any help. I've deleted "qtwaininterface" and "qtwainsubstitute".

The problem is that on "BOOL CTwain::ProcessMessage(MSG msg)" method, the line "if(GetRC() != TWRC_NOTDSEVENT)" always returns "TWRC_NOTDSEVENT" and so, the application never recives TWAIN messages.

I would like to port this to Qt 4 for everyone to want to use it and I will send the final version to the author "Stephan Stapel".

Thanks,

Hi,

Any Idea why it don't recive TWAIN messages?
I have scanned only one image by calling "TransferImage()" on "CTwain::Acquire(int numImages)" method:

Code:

---

BOOL CTwain::Acquire(int numImages)
{
    if(DSOpen() || OpenSource())
    {
        SetImageCount(numImages);
        EnableSource(false);
        TransferImage();
        return(true);
        /*
        if(SetImageCount(numImages))
        {
            if(EnableSource(false))
            {
                return TRUE;
            }
        }
        */
    }
    return FALSE;
}

---

If you call "EnableSource(true)", the UI of scanner will appear but don't response to the scan button, but response to preview button.

Thanks,

Did you ever get the scanning to work? I am interested in it too.

Thank you.

I'm also looking for the same solution. if you have already find out the way to write your own application using TWAIN, please post it here, so that we can also use it.

Hi,

I have no much time to explain how I make it works. Cut here, paste there, ... I need it for a commercial application that only scans gray images.
The attached files have been modified.
Here is some explanation how to use it:

1) Declare a "QTwain" class pointer in your application and create a new QTwain instance in the FIRST code line of your MainWindow class using "this" as the parent.

Code:

---

QTwain* m_pqTwain = new QTwain(this);

---

2)Redefine the method "showEvent(QShowEvent* event)" on your MainWindow class and there call "m_pqTwain->setParent(this)".

3)Redefine the method "winEvent(MSG* pMsg,long* result)" with this call "return(m_pqTwain->processMessage(*pMsg) == TRUE);

4)Now, here is the hack:
To enumerate the sources(Scanner devices) I use "m_pTwain->initTwain()" and "m_pTwain->enumerateSources()"
To scan an image I use "m_pTwain->ReleaseTwain()", and "m_pTwain->initTwain()" again. Select the selected source using "m_pTwain->selectSource(m_iScannerDeviceIndex)". Configure the Scan device using "m_pTwain->selectDepth(8)", "m_pTwain->selectResolutionX(200)", "m_pTwain->selectResolutionY(200)". Finally, start the capture using "m_pTwain->acquire()". Note that if I don't release the Twain dll every time I get a scan finished, the messages are lost(don't know where, maybe in the space, .. :-P)

5) Use a Timer to let the main application check every X seconds if the scanner has finished. You have to check the "m_pTwain->m_bFiEscaneig" that will be true if it have finished. Oops, before starting the capture you have to set it to false by hand.

6) connect the SIGNAL "emetreImatge(QImage)" to your SLOT to get the image.

I know that is not a good solution to use but it works for my purpose. I hope anyone can hack it a little bit and let other people use it. It's not well documented and also, the comments and my defined variables will be in Catalan language(a language used into a region of Spain that includes Barcelona).

Perdona Nyaw, pero al bajarme los dos ficheros qtwain.zip y QtTwainScan.zip e intentarlos abrir se produce un error: "Final inesperado del archivo".
Como estoy interesado en poder añadir capacidades para escanear a una aplicación que estoy haciendo, podrÃ*as facilitarnos esos archivos correctamente.

¿Has hecho algún progreso al respecto?

Muchas gracias.

Hi,

Dear jokinb,
Don't post spanish posts on this forum as people can't read it.
I just downloaded the file and uncopressed using WinRAR and it had no error.
Respect to the progress on this, I said that it works not very well but it is perfect fot my application.
Maybe the newest 2 version of TWAIN will be better.
Of course you can send me private messages written in spanish.

I will write in English.
I have domnloaded the qtwain.zip file and I have got the same error. "Unexpected end of archive".

It is posible to use the WIA tecnology in Qt?
Thanks
Jokinb

Hi,

Try this, I only donwloaded the file from this forum uncompressed and compressed again.

Finally , with a lot of tricks I have got the qtwain file downloaded.
How many files are in. I get six. It is ok.?

Thanks
Jokinb

Hi,

Yes, there are 6 files.

I don't understand why you have to use a lot of tricks. Is there any other person that can try downloading the file and decompress it to check if there is any error on uncompress it?

the notice on the forum says that they have some problems into attachments before 1st sep 2010. may be that is the issue. the new file is good.

I don´t Know but the newest file had the same problem that the first one to open. I don´t Know why but... I tried with diferents programs to deskompress the file . The same message..."end of file corrupt"... "the file can´t bee opened"....

Finnally i got the file opened in an unusual way. I have the six files and must find time to study them.

Thanks

Jokinb

Hello all,

Have you got any simple example to use this class ?
I have try to acquire and save 1 A4 image :

Code:

---

#include <iostream>
#include "qtwain.h"
 
using namespace std;
 
int main(int agc, char **argv)
{
        QTwain t;
        t.initTwain();
        if(t.isValidDriver() && t.selectSource())
        {
                t.setResolutionY(1654);
                t.setResolutionX(2339);
                t.setDepth(1);
                t.acquire(1);
        }
    return 0;
}

---

But it doesn't work; why ?

For your help, by advance, thanks.

The 'example' in the code!
Just look in there.

Code:

---

void QtTwainScan::scan()
{
	if (!m_pTwain->initTwain())
		qWarning("initTwain() call not successful!");
	else
		if (!m_pTwain->selectSource())
			qWarning("selectSource() call not successful!");
		else
			if (!m_pTwain->acquire())
				qWarning("acquire() call not successful!");
}

---

Quote:

---

Originally Posted by high_flyer

The 'example' in the code!
Just look in there.

Code:

---

void QtTwainScan::scan()
{
	if (!m_pTwain->initTwain())
		qWarning("initTwain() call not successful!");
	else
		if (!m_pTwain->selectSource())
			qWarning("selectSource() call not successful!");
		else
			if (!m_pTwain->acquire())
				qWarning("acquire() call not successful!");
}

---

---

Happy new year.
I have tried this (with QtCreator or the CLI) :

Code:

---

#include <QApplication>
#include "qtwain.h"
 
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QTwain m_pTwain;
    if (!m_pTwain.initTwain())
        qWarning("initTwain() call not successful!");
    else
        if (!m_pTwain.selectSource())
            qWarning("selectSource() call not successful!");
        else
            if (!m_pTwain.acquire())
                qWarning("acquire() call not successful!");
    return app.exec();
}

---

But I still have a segmentation error,
Have you ever have this bug ?

By advance,
Thanks

Happy new year to you too! :)

I just had a 2 seconds look - to see if I could help you getting started.
I didn't look further.
But you should.
Maybe there are some initializations needed to be done, I don't know, stuff like that.
Follow the application in the debugger, and see exactly where it crashes, it will tell you a lot about what the problem is.

It is probably because the QTwain class requires an event loop to be running, and until you call app.exec(), there is no event loop.

Your code is fundamentally different from the example in the previous post in the thread. You need to move your twain code into a method that gets called after the event loop has started.

Good point.

Quote:

---

Originally Posted by d_stranz

It is probably because the QTwain class requires an event loop to be running, and until you call app.exec(), there is no event loop.

Your code is fundamentally different from the example in the previous post in the thread. You need to move your twain code into a method that gets called after the event loop has started.

---

Thank you very much,
I create a Widget QTwain and used according to your examples, but I have not found a way to save the image acquired only by the interface.
The only way, according to my investigations, would be to uncomment the lines 92 to 95 of qtwain.cpp, and yet I know not how to get the values to pass as an argument to CopyImage.

For your help,
By advance,
Thanks