Приостановить сканирование TWAIN (остановить устройство подачи)

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Многие TWAIN сканеры оснащены устройствами автоматической подачи документов. Некоторые из этих TWAIN сканеров позволяют остановить устройство подачи, т.е. приостановить процесс получения изображений. Метод Vintasoft.Twain.Device.StopFeeder позволяет остановить устройство подачи документов.

Вот C#/VB.NET код, который демонстрирует, как начать асинхронное сканирование изображений, остановить устройство подачи документов и продолжить асинхронное сканирование изображений:

static bool _isScanningFinished;
static int _step;
static int _imageCount;


/// <summary>
/// Synchronously acquires one image from TWAIN device, stops the document feeder, scans the second image.
/// </summary>
public static void AsynchronouslyAcquireImageFromTwainDevice_StopFeeder_ContinueImageTransfer()
{
    _isScanningFinished = false;
    _step = 0;
    _imageCount = 0;

    // create the device manager
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        deviceManager.IsTwain2Compatible = true;
        // open the device manager
        deviceManager.Open();

        // get the device
        string deviceName = "KODAK Scanner: i5000";
        Vintasoft.Twain.Device device = deviceManager.Devices.Find(deviceName);
        if (device == null)
            throw new System.ApplicationException(string.Format("Device '{0}' is not found.", deviceName));

        // subscribe to device events
        SubscribeToDeviceEvents(device);

        // disable device UI
        device.ShowUI = false;
        // specify that device must be closed after scan
        device.DisableAfterAcquire = true;

        // open the device
        device.Open();
        // specify that 2 images must be acquired from scanner
        device.XferCount = 2;

        // run asynchronous image acqusition
        device.Acquire();
        // wait while feeder will be stopped
        while (!_isScanningFinished)
        {
            System.Windows.Forms.Application.DoEvents();
        }

        if (_imageCount != 1)
        {
            // unsubscribe from device events
            UnsubscribeFromDeviceEvents(device);

            throw new System.ApplicationException("Wrong acquired image count.");
        }

        if (device.State != Vintasoft.Twain.DeviceState.TransferReady)
        {
            // unsubscribe from device events
            UnsubscribeFromDeviceEvents(device);

            throw new System.ApplicationException("Feeder is NOT stopped.");
        }
        System.Console.WriteLine("Feeder is stopped.");

        _isScanningFinished = false;
        // run asynchronous image acqusition
        device.Acquire();
        // wait while image scan will be finished
        while (!_isScanningFinished)
        {
            System.Windows.Forms.Application.DoEvents();
        }

        // unsubscribe from device events
        UnsubscribeFromDeviceEvents(device);

        if (_imageCount != 2)
            throw new System.ApplicationException("Wrong acquired image count.");

        // close the device
        device.Close();
    }
}

/// <summary>
/// Image is acquired.
/// </summary>
private static void device_ImageAcquired(object sender, Vintasoft.Twain.ImageAcquiredEventArgs e)
{
    System.Console.WriteLine("Image is acquired.");
    // increment image count
    _imageCount++;

    // if we need stop the feeder
    if (_step == 0)
    {
        // get reference to the device
        Vintasoft.Twain.Device device = (Vintasoft.Twain.Device)sender;
        // stop the feeder
        device.StopFeeder();

        // specify that feeder is stopped
        _step = 1;
        _isScanningFinished = true;
    }
}

/// <summary>
/// Scan is completed.
/// </summary>
private static void device_ScanCompleted(object sender, System.EventArgs e)
{
    System.Console.WriteLine("Scan is completed.");
}

/// <summary>
/// Scan is canceled.
/// </summary>
private static void device_ScanCanceled(object sender, System.EventArgs e)
{
    System.Console.WriteLine("Scan is canceled.");
}

/// <summary>
/// Scan is failed.
/// </summary>
private static void device_ScanFailed(object sender, Vintasoft.Twain.ScanFailedEventArgs e)
{
    System.Console.WriteLine(string.Format("Scan is failed: {0}.", e.ErrorString));
}

/// <summary>
/// Scan is finished.
/// </summary>
private static void device_ScanFinished(object sender, System.EventArgs e)
{
    _isScanningFinished = true;
}

/// <summary>
/// Subscribes to the device events.
/// </summary>
private static void SubscribeToDeviceEvents(Vintasoft.Twain.Device device)
{
    device.ImageAcquired += new System.EventHandler<Vintasoft.Twain.ImageAcquiredEventArgs>(device_ImageAcquired);
    device.ScanCompleted += new System.EventHandler(device_ScanCompleted);
    device.ScanCanceled += new System.EventHandler(device_ScanCanceled);
    device.ScanFailed += new System.EventHandler<Vintasoft.Twain.ScanFailedEventArgs>(device_ScanFailed);
    device.ScanFinished += new System.EventHandler(device_ScanFinished);
}

/// <summary>
/// Unsubscribes from the device events.
/// </summary>
private static void UnsubscribeFromDeviceEvents(Vintasoft.Twain.Device device)
{
    device.ImageAcquired -= new System.EventHandler<Vintasoft.Twain.ImageAcquiredEventArgs>(device_ImageAcquired);
    device.ScanCompleted -= new System.EventHandler(device_ScanCompleted);
    device.ScanCanceled -= new System.EventHandler(device_ScanCanceled);
    device.ScanFailed -= new System.EventHandler<Vintasoft.Twain.ScanFailedEventArgs>(device_ScanFailed);
    device.ScanFinished -= new System.EventHandler(device_ScanFinished);
}

VB.NET

Shared _isScanningFinished As Boolean
Shared _step As Integer
Shared _imageCount As Integer


''' <summary>
''' Synchronously acquires one image from TWAIN device, stops the document feeder, scans the second image.
''' </summary>
Public Shared Sub AsynchronouslyAcquireImageFromTwainDevice_StopFeeder_ContinueImageTransfer()
        _isScanningFinished = False
        _step = 0
        _imageCount = 0

        ' create the device manager
        Using deviceManager As New Vintasoft.Twain.DeviceManager()
                deviceManager.IsTwain2Compatible = True
                ' open the device manager
                deviceManager.Open()

                ' get the device
                Dim deviceName As String = "KODAK Scanner: i5000"
                Dim device As Vintasoft.Twain.Device = deviceManager.Devices.Find(deviceName)
                If device Is Nothing Then
                        Throw New System.ApplicationException(String.Format("Device '{0}' is not found.", deviceName))
                End If

                ' subscribe to device events
                SubscribeToDeviceEvents(device)

                ' disable device UI
                device.ShowUI = False
                ' specify that device must be closed after scan
                device.DisableAfterAcquire = True

                ' open the device
                device.Open()
                ' specify that 2 images must be acquired from scanner
                device.XferCount = 2

                ' run asynchronous image acqusition
                device.Acquire()
                ' wait while feeder will be stopped
                While Not _isScanningFinished
                        System.Windows.Forms.Application.DoEvents()
                End While

                If _imageCount <> 1 Then
                        ' unsubscribe from device events
                        UnsubscribeFromDeviceEvents(device)

                        Throw New System.ApplicationException("Wrong acquired image count.")
                End If

                If device.State <> Vintasoft.Twain.DeviceState.TransferReady Then
                        ' unsubscribe from device events
                        UnsubscribeFromDeviceEvents(device)

                        Throw New System.ApplicationException("Feeder is NOT stopped.")
                End If
                System.Console.WriteLine("Feeder is stopped.")

                _isScanningFinished = False
                ' run asynchronous image acqusition
                device.Acquire()
                ' wait while image scan will be finished
                While Not _isScanningFinished
                        System.Windows.Forms.Application.DoEvents()
                End While

                ' unsubscribe from device events
                UnsubscribeFromDeviceEvents(device)

                If _imageCount <> 2 Then
                        Throw New System.ApplicationException("Wrong acquired image count.")
                End If

                ' close the device
                device.Close()
        End Using
End Sub

''' <summary>
''' Image is acquired.
''' </summary>
Private Shared Sub device_ImageAcquired(sender As Object, e As Vintasoft.Twain.ImageAcquiredEventArgs)
        System.Console.WriteLine("Image is acquired.")
        ' increment image count
        _imageCount += 1

        ' if we need stop the feeder
        If _step = 0 Then
                ' get reference to the device
                Dim device As Vintasoft.Twain.Device = DirectCast(sender, Vintasoft.Twain.Device)
                ' stop the feeder
                device.StopFeeder()

                ' specify that feeder is stopped
                _step = 1
                _isScanningFinished = True
        End If
End Sub

''' <summary>
''' Scan is completed.
''' </summary>
Private Shared Sub device_ScanCompleted(sender As Object, e As System.EventArgs)
        System.Console.WriteLine("Scan is completed.")
End Sub

''' <summary>
''' Scan is canceled.
''' </summary>
Private Shared Sub device_ScanCanceled(sender As Object, e As System.EventArgs)
        System.Console.WriteLine("Scan is canceled.")
End Sub

''' <summary>
''' Scan is failed.
''' </summary>
Private Shared Sub device_ScanFailed(sender As Object, e As Vintasoft.Twain.ScanFailedEventArgs)
        System.Console.WriteLine(String.Format("Scan is failed: {0}.", e.ErrorString))
End Sub

''' <summary>
''' Scan is finished.
''' </summary>
Private Shared Sub device_ScanFinished(sender As Object, e As System.EventArgs)
        _isScanningFinished = True
End Sub

''' <summary>
''' Subscribes to the device events.
''' </summary>
Private Shared Sub SubscribeToDeviceEvents(device As Vintasoft.Twain.Device)
        AddHandler device.ImageAcquired, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiredEventArgs)(AddressOf device_ImageAcquired)
        AddHandler device.ScanCompleted, New System.EventHandler(AddressOf device_ScanCompleted)
        AddHandler device.ScanCanceled, New System.EventHandler(AddressOf device_ScanCanceled)
        AddHandler device.ScanFailed, New System.EventHandler(Of Vintasoft.Twain.ScanFailedEventArgs)(AddressOf device_ScanFailed)
        AddHandler device.ScanFinished, New System.EventHandler(AddressOf device_ScanFinished)
End Sub

''' <summary>
''' Unsubscribes from the device events.
''' </summary>
Private Shared Sub UnsubscribeFromDeviceEvents(device As Vintasoft.Twain.Device)
        RemoveHandler device.ImageAcquired, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiredEventArgs)(AddressOf device_ImageAcquired)
        RemoveHandler device.ScanCompleted, New System.EventHandler(AddressOf device_ScanCompleted)
        RemoveHandler device.ScanCanceled, New System.EventHandler(AddressOf device_ScanCanceled)
        RemoveHandler device.ScanFailed, New System.EventHandler(Of Vintasoft.Twain.ScanFailedEventArgs)(AddressOf device_ScanFailed)
        RemoveHandler device.ScanFinished, New System.EventHandler(AddressOf device_ScanFinished)
End Sub

Вот C#/VB.NET код, который демонстрирует, как запустить синхронное сканирование изображений, остановить устройство подачи документов и продолжить синхронное сканирование изображений:

/// <summary>
/// Synchronously acquires one image from TWAIN device, stops the document feeder, scans the second image.
/// </summary>
public static void SynchronouslyAcquireImageFromTwainDevice_StopFeeder_ContinueImageTransfer()
{
    int imageCount = 0;

    // create the device manager
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        deviceManager.IsTwain2Compatible = true;
        // open the device manager
        deviceManager.Open();

        // get the device
        string deviceName = "KODAK Scanner: i5000";
        Vintasoft.Twain.Device device = deviceManager.Devices.Find(deviceName);
        if (device == null)
            throw new System.ApplicationException(string.Format("Device '{0}' is not found.", deviceName));

        // disable device UI
        device.ShowUI = false;
        // specify that device must be closed after scan
        device.DisableAfterAcquire = true;

        // open the device
        device.Open();
        // specify that 2 images must be acquired from scanner
        device.XferCount = 2;

        // run asynchronous image acquisition
        Vintasoft.Twain.AcquireModalState acquireModalState = Vintasoft.Twain.AcquireModalState.None;
        do
        {
            acquireModalState = device.AcquireModal();
            switch (acquireModalState)
            {
                case Vintasoft.Twain.AcquireModalState.ImageAcquired:
                    System.Console.WriteLine("Image is acquired.");
                    if (device.AcquiredImage != null)
                        device.AcquiredImage.Dispose();

                    imageCount++;

                    // stop the feeder
                    device.StopFeeder();
                    break;

                case Vintasoft.Twain.AcquireModalState.ScanCompleted:
                    System.Console.WriteLine("Scan is completed.");
                    break;

                case Vintasoft.Twain.AcquireModalState.ScanCanceled:
                    System.Console.WriteLine("Scan is canceled.");
                    break;

                case Vintasoft.Twain.AcquireModalState.ScanFailed:
                    System.Console.WriteLine(string.Format("Scan is failed: {0}.", device.ErrorString));
                    break;
            }
        }
        while (acquireModalState != Vintasoft.Twain.AcquireModalState.None);

        if (imageCount != 1)
            throw new System.ApplicationException("Wrong acquired image count.");

        if (device.State != Vintasoft.Twain.DeviceState.TransferReady)
            throw new System.ApplicationException("Feeder is NOT stopped.");
        System.Console.WriteLine("Feeder is stopped.");

        // continue asynchronous image acquisition
        do
        {
            acquireModalState = device.AcquireModal();
            switch (acquireModalState)
            {
                case Vintasoft.Twain.AcquireModalState.ImageAcquired:
                    System.Console.WriteLine("Image is acquired.");

                    if (device.AcquiredImage != null)
                        device.AcquiredImage.Dispose();

                    imageCount++;
                    break;

                case Vintasoft.Twain.AcquireModalState.ScanCompleted:
                    System.Console.WriteLine("Scan is completed.");
                    break;

                case Vintasoft.Twain.AcquireModalState.ScanCanceled:
                    System.Console.WriteLine("Scan is canceled.");
                    break;

                case Vintasoft.Twain.AcquireModalState.ScanFailed:
                    System.Console.WriteLine(string.Format("Scan is failed: {0}.", device.ErrorString));
                    break;
            }
        }
        while (acquireModalState != Vintasoft.Twain.AcquireModalState.None);

        if (imageCount != 2)
            throw new System.ApplicationException("Wrong acquired image count.");

        // close the device
        device.Close();
    }
}

VB.NET

''' <summary>
''' Synchronously acquires one image from TWAIN device, stops the document feeder, scans the second image.
''' </summary>
Public Shared Sub SynchronouslyAcquireImageFromTwainDevice_StopFeeder_ContinueImageTransfer()
        Dim imageCount As Integer = 0

        ' create the device manager
        Using deviceManager As New Vintasoft.Twain.DeviceManager()
                deviceManager.IsTwain2Compatible = True
                ' open the device manager
                deviceManager.Open()

                ' get the device
                Dim deviceName As String = "KODAK Scanner: i5000"
                Dim device As Vintasoft.Twain.Device = deviceManager.Devices.Find(deviceName)
                If device Is Nothing Then
                        Throw New System.ApplicationException(String.Format("Device '{0}' is not found.", deviceName))
                End If

                ' disable device UI
                device.ShowUI = False
                ' specify that device must be closed after scan
                device.DisableAfterAcquire = True

                ' open the device
                device.Open()
                ' specify that 2 images must be acquired from scanner
                device.XferCount = 2

                ' run asynchronous image acquisition
                Dim acquireModalState As Vintasoft.Twain.AcquireModalState = Vintasoft.Twain.AcquireModalState.None
                Do
                        acquireModalState = device.AcquireModal()
                        Select Case acquireModalState
                                Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                                        System.Console.WriteLine("Image is acquired.")
                                        If device.AcquiredImage IsNot Nothing Then
                                                device.AcquiredImage.Dispose()
                                        End If

                                        imageCount += 1

                                        ' stop the feeder
                                        device.StopFeeder()
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ScanCompleted
                                        System.Console.WriteLine("Scan is completed.")
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ScanCanceled
                                        System.Console.WriteLine("Scan is canceled.")
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ScanFailed
                                        System.Console.WriteLine(String.Format("Scan is failed: {0}.", device.ErrorString))
                                        Exit Select
                        End Select
                Loop While acquireModalState <> Vintasoft.Twain.AcquireModalState.None

                If imageCount <> 1 Then
                        Throw New System.ApplicationException("Wrong acquired image count.")
                End If

                If device.State <> Vintasoft.Twain.DeviceState.TransferReady Then
                        Throw New System.ApplicationException("Feeder is NOT stopped.")
                End If
                System.Console.WriteLine("Feeder is stopped.")

                ' continue asynchronous image acquisition
                Do
                        acquireModalState = device.AcquireModal()
                        Select Case acquireModalState
                                Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                                        System.Console.WriteLine("Image is acquired.")

                                        If device.AcquiredImage IsNot Nothing Then
                                                device.AcquiredImage.Dispose()
                                        End If

                                        imageCount += 1
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ScanCompleted
                                        System.Console.WriteLine("Scan is completed.")
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ScanCanceled
                                        System.Console.WriteLine("Scan is canceled.")
                                        Exit Select

                                Case Vintasoft.Twain.AcquireModalState.ScanFailed
                                        System.Console.WriteLine(String.Format("Scan is failed: {0}.", device.ErrorString))
                                        Exit Select
                        End Select
                Loop While acquireModalState <> Vintasoft.Twain.AcquireModalState.None

                If imageCount <> 2 Then
                        Throw New System.ApplicationException("Wrong acquired image count.")
                End If

                ' close the device
                device.Close()
        End Using
End Sub

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