Using a scanner without dialogs in C#

问题:

I'm building a .Net 4.0 application for remote control of a scanner device. I have tried both TWAIN and WIA libraries, but I have the same problem. Scanning images without scanner selection and scanning settings dialogs.

I found a useful article on WIA scripting in .Net, and modified it to this:

private Image Scan(string deviceName)
{
    WiaClass wiaManager = null;       // WIA manager COM object
    CollectionClass wiaDevs = null;   // WIA devices collection COM object
    ItemClass wiaRoot = null;         // WIA root device COM object
    CollectionClass wiaPics = null;   // WIA collection COM object
    ItemClass wiaItem = null;         // WIA image COM object

    try
    {
        // create COM instance of WIA manager
        wiaManager = new WiaClass();

        // call Wia.Devices to get all devices
        wiaDevs = wiaManager.Devices as CollectionClass;
        if ((wiaDevs == null) || (wiaDevs.Count == 0))
        {
            throw new Exception("No WIA devices found!");
        }

        object device = null;
        foreach (IWiaDeviceInfo currentDevice in wiaManager.Devices)
        {
            if (currentDevice.Name == deviceName)
            {
                device = currentDevice;
                break;
            }
        }

        if (device == null)
        {
            throw new Exception
            (
                "Device with name \"" + 
                deviceName + 
                "\" could not be found."
            );
        }

        // select device
        wiaRoot = (ItemClass)wiaManager.Create(ref device); 

        // something went wrong
        if (wiaRoot == null)
        {
            throw new Exception
            (
                "Could not initialize device \"" + 
                deviceName + "\"."
            );
        }

        wiaPics = wiaRoot.GetItemsFromUI
        (
            WiaFlag.SingleImage,
            WiaIntent.ImageTypeColor
        ) as CollectionClass;

        if (wiaPics == null || wiaPics.Count == 0)
        {
            throw new Exception("Could not scan image.");
        }

        Image image = null;

        // enumerate all the pictures the user selected
        foreach (object wiaObj in wiaPics)
        {
            if (image == null)
            {
                wiaItem = (ItemClass)Marshal.CreateWrapperOfType
                (
                    wiaObj, typeof(ItemClass)
                );

                // create temporary file for image
                string tempFile = Path.GetTempFileName();

                // transfer picture to our temporary file
                wiaItem.Transfer(tempFile, false);

                // create Image instance from file
                image = Image.FromFile(tempFile);
            }

            // release enumerated COM object
            Marshal.ReleaseComObject(wiaObj);
        }

        if (image == null)
        {
            throw new Exception("Error reading scanned image.");
        }

        return image;
    }
    finally
    {
        // release WIA image COM object
        if (wiaItem != null)
            Marshal.ReleaseComObject(wiaItem);

        // release WIA collection COM object
        if (wiaPics != null)
            Marshal.ReleaseComObject(wiaPics);

        // release WIA root device COM object
        if (wiaRoot != null)
            Marshal.ReleaseComObject(wiaRoot);

        // release WIA devices collection COM object
        if (wiaDevs != null)
            Marshal.ReleaseComObject(wiaDevs);

        // release WIA manager COM object
        if (wiaManager != null)
            Marshal.ReleaseComObject(wiaManager);
    }
}

With this I actually managed to select the device from configuration (input parameter of the Scan method) and retrieve the resulting image after scan.

But the problem with scanning options dialog (Scan using DEVICENAME). As this is a remote control application, dialog will not be visible to the user, so I need to either skip it using default settings, or use settings from a configuration if necessary.

Scanning options dialog:

回答1:

First off, many thanks to Miljenko Barbir for his above solution, it works great.

I would like to add that if you want zero dialogs, you can use (from Milijenko's demo code)

WIA.ImageFile image = item.Transfer(wiaFormatBMP);

instead of

WIA.ImageFile image = (WIA.ImageFile)wiaCommonDialog.ShowTransfer(item, wiaFormatBMP, false);

This basically removes the progress bar as well, so you get scanning without any dialogs.

回答2:

// show scanner view 
guif.ShowUI = 0;
guif.ModalUI = 0;

You can see in this code that's I've implemented.