Отмена получения изображений от TWAIN сканера

В этом разделе

Если вы хотите отменить получение изображения, выполните следующие действия:

Вызовите метод Vintasoft.Twain.Device.CancelTransfer.
Дождитесь события Vintasoft.Twain.Device.ScanCanceled, если вы получаете изображения асинхронно.
Подождите, пока метод Vintasoft.Twain.Device.AcquireModal вернет значение Vintasoft.Twain.AcquireModalState.ScanCanceled, если вы получаете изображения в модальном цикле.

Некоторые высокоскоростные TWAIN-сканеры имеют внутренний буфер, и TWAIN-сканеры кэшируют полученные изображения в буфере, если TWAIN-сканер быстрее приложения, которое обрабатывает полученные изображения. Изображения, которые кэшируются во внутреннем буфере, будут потеряны, если вы отмените процесс получения изображений. Вы можете приостановить процесс получения изображения (вместо отмены получения изображения), если вам нужно сохранить все полученные изображения.

Вот пример, который демонстрирует, как отменить асинхронную передачу изображений от TWAIN сканера:

namespace TwainExamples_CSharp
{
    class AsyncScan_Cancel
    {

        static bool _isScanFinished;
        static bool _isScanCanceled;



        /// <summary>
        /// This method scans one image and cancels image scan.
        /// </summary>
        public static void ScanOneImageAndCancelScan()
        {
            _isScanFinished = false;
            _isScanCanceled = false;

            // 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
                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);

                // 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 scan will be finished
                while (!_isScanFinished)
                {
                    System.Windows.Forms.Application.DoEvents();
                }

                if (!_isScanCanceled)
                    throw new System.ApplicationException("Scan is NOT canceled.");

                // unsubscribe from device events
                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);

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

        static void device_ImageAcquired(object sender, Vintasoft.Twain.ImageAcquiredEventArgs e)
        {
            // get reference to the device
            Vintasoft.Twain.Device device = (Vintasoft.Twain.Device)sender;
            // cancel image scan
            device.CancelTransfer();
            System.Console.WriteLine("Feeder is stopped.");
        }

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

        static void device_ScanCanceled(object sender, System.EventArgs e)
        {
            _isScanCanceled = true;
            System.Console.WriteLine("Scan is canceled.");
        }

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

        static void device_ScanFinished(object sender, System.EventArgs e)
        {
            _isScanFinished = true;            
        }

    }
}

VB.NET

Class AsyncScan_Cancel

    Shared _isScanFinished As Boolean
    Shared _isScanCanceled As Boolean



    ''' <summary>
    ''' This method scans one image and cancels image scan.
    ''' </summary>
    Public Shared Sub ScanOneImageAndCancelScan()
        _isScanFinished = False
        _isScanCanceled = False

        ' 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
            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)

            ' 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 scan will be finished
            While Not _isScanFinished
                System.Windows.Forms.Application.DoEvents()
            End While

            If Not _isScanCanceled Then
                Throw New ApplicationException("Scan is NOT canceled.")
            End If

            ' unsubscribe from device events
            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)

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

    Private Shared Sub device_ImageAcquired(ByVal sender As Object, ByVal e As Vintasoft.Twain.ImageAcquiredEventArgs)
        Console.WriteLine("Image is acquired.")
        ' get reference to the device
        Dim device As Vintasoft.Twain.Device = DirectCast(sender, Vintasoft.Twain.Device)
        ' cancel image scan
        device.CancelTransfer()
    End Sub

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

    Private Shared Sub device_ScanCanceled(ByVal sender As Object, ByVal e As EventArgs)
        _isScanCanceled = True
        Console.WriteLine("Scan is canceled.")
    End Sub

    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

    Private Shared Sub device_ScanFinished(ByVal sender As Object, ByVal e As EventArgs)
        _isScanFinished = True
    End Sub

End Class

Вот пример, который демонстрирует, как отменить синхронную передачу изображений от TWAIN сканера:

namespace TwainExamples_CSharp
{
    class SyncScan_Cancel
    {

        /// <summary>
        /// This method scans one image and cancels image scan.
        /// </summary>
        public static void ScanOneImageAndCancelScan()
        {
            bool isScanCanceled = false;

            // 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();

                            // cancel image scan
                            device.CancelTransfer();
                            break;

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

                        case Vintasoft.Twain.AcquireModalState.ScanCanceled:
                            isScanCanceled = true;
                            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 (!isScanCanceled)
                    throw new System.ApplicationException("Scan is NOT canceled.");

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

    }
}

VB.NET

Class SyncScan_Cancel

        ''' <summary>
        ''' This method scans one image and cancels image scan.
        ''' </summary>
        Public Shared Sub ScanOneImageAndCancelScan()
                Dim isScanCanceled As Boolean = False

                ' 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 asynchronous 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

                                                ' cancel image scan
                                                device.CancelTransfer()
                                                Exit Select

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

                                        Case Vintasoft.Twain.AcquireModalState.ScanCanceled
                                                isScanCanceled = True
                                                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 Not isScanCanceled Then
                                Throw New ApplicationException("Scan is NOT canceled.")
                        End If

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

End Class

Отправить отзыв