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 изображения. Метод Vintasoft.Twain.Device.StopFeeder позволяет остановить устройство подачи.

Вот пример, который демонстрирует, как начать асинхронное получение изображения, остановить устройство подачи документов и продолжить асинхронное получение изображения:

namespace TwainExamples_CSharp
{
    class AsyncScan_StopFeeder
    {

        static bool _isScanFinished;
        static int _step;
        static int _imageCount;



        /// <summary>
        /// Scans the first image, stops the document feeder, scans the second image.
        /// </summary>
        public static void ScanImage_StopFeeder_ScanImage()
        {
            _isScanFinished = 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 (!_isScanFinished)
                {
                    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.");

                _isScanFinished = false;
                // run asynchronous image acqusition
                device.Acquire();
                // wait while image scan will be finished
                while (!_isScanFinished)
                {
                    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;
                _isScanFinished = 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)
        {
            _isScanFinished = 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

Class AsyncScan_StopFeeder

    Shared _isScanFinished As Boolean
    Shared _step As Integer
    Shared _imageCount As Integer



    ''' <summary>
    ''' Scans the first image, stops the document feeder, scans the second image.
    ''' </summary>
    Public Shared Sub ScanImage_StopFeeder_ScanImage()
        _isScanFinished = 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 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 _isScanFinished
                System.Windows.Forms.Application.DoEvents()
            End While

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

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

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

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

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

            ' unsubscribe from device events
            UnsubscribeFromDeviceEvents(device)

            If _imageCount <> 2 Then
                Throw New 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(ByVal sender As Object, ByVal e As Vintasoft.Twain.ImageAcquiredEventArgs)
        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
            _isScanFinished = True
        End If
    End Sub

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

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

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

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

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

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

End Class

Вот пример, который демонстрирует, как запустить синхронное получение изображения, остановить устройство подачи документов и продолжить синхронное получение изображения:

namespace TwainExamples_CSharp
{
    class SyncScan_StopFeeder
    {

        /// <summary>
        /// This method scans the first image, stops the document feeder,
        /// scans the second image.
        /// </summary>
        public static void ScanImage_StopFeeder_ScanImage()
        {
            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

Class SyncScan_StopFeeder

    ''' <summary>
    ''' This method scans the first image, stops the document feeder,
    ''' scans the second image.
    ''' </summary>
    Public Shared Sub ScanImage_StopFeeder_ScanImage()
        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 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 synchronous image acquisition
            Dim acquireModalState1 As Vintasoft.Twain.AcquireModalState = Vintasoft.Twain.AcquireModalState.None
            Do
                acquireModalState1 = device.AcquireModal()
                Select Case acquireModalState1
                    Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                        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
                        Console.WriteLine("Scan is completed.")
                        Exit Select

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

                    Case Vintasoft.Twain.AcquireModalState.ScanFailed
                        Console.WriteLine(String.Format("Scan is failed: {0}.", device.ErrorString))
                        Exit Select
                End Select
            Loop While acquireModalState1 <> Vintasoft.Twain.AcquireModalState.None

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

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

            ' continue asynchronous image acquisition
            Do
                acquireModalState1 = device.AcquireModal()
                Select Case acquireModalState1
                    Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                        Console.WriteLine("Image is acquired.")

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

                        imageCount = imageCount + 1
                        Exit Select

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

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

                    Case Vintasoft.Twain.AcquireModalState.ScanFailed
                        Console.WriteLine(String.Format("Scan is failed: {0}.", device.ErrorString))
                        Exit Select
                End Select
            Loop While acquireModalState1 <> Vintasoft.Twain.AcquireModalState.None

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

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

End Class

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