Acquire images from TWAIN scanner asynchronously
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VintaSoft Twain .NET SDK allows to acquire images from TWAIN scanner asynchronously.
Here are steps, which should be made for asynchronous acquisition of images from TWAIN device:
- Open TWAIN device manager.
- Select TWAIN device.
- Subscribe to the events of TWAIN device: Device.ImageAcquired, Device.ScanFinished, etc.
- Open TWAIN device.
- Set TWAIN device settings.
- Start the asynchronous acquisition of images from TWAIN device by calling Device.Acquire method.
- Retrieve acquired image one by one while the Device.ImageAcquired event occurs.
- Stop image acquisition process when the Device.ScanCompleted event occurs.
Here is an example that demonstrates how to acquire images from TWAIN device and save acquired images to a multipage TIFF file:
static bool _isScanningFinished;
/// <summary>
/// Asynchronously acquires images from TWAIN device.
/// </summary>
public static void AsynchronouslyAcquireImageFromTwainDevice()
{
_isScanningFinished = 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
SubscribeToDeviceEvents(device);
// disable device UI
device.ShowUI = false;
// set Memory transfer mode
device.TransferMode = Vintasoft.Twain.TransferMode.Memory;
// open the device
device.Open();
// specify that black-white images must be acquired
device.PixelType = Vintasoft.Twain.PixelType.BW;
// specify the threshold for acquired images
device.Threshold = 128;
// set the inches as unit of measure
device.UnitOfMeasure = Vintasoft.Twain.UnitOfMeasure.Inches;
device.Resolution = new Vintasoft.Twain.Resolution(300f, 300f);
// run asynchronous image acqusition
device.Acquire();
// wait while feeder will be stopped
while (!_isScanningFinished)
{
System.Windows.Forms.Application.DoEvents();
}
// unsubscribe from device events
UnsubscribeFromDeviceEvents(device);
// close the device
device.Close();
}
}
/// <summary>
/// Image acquisition is in progress.
/// </summary>
private static void device_ImageAcquiringProgress(object sender, Vintasoft.Twain.ImageAcquiringProgressEventArgs e)
{
// update progress bar
}
/// <summary>
/// Image is acquired.
/// </summary>
private static void device_ImageAcquired(object sender, Vintasoft.Twain.ImageAcquiredEventArgs e)
{
// add the acquired image to a TIFF file
e.Image.Save(System.IO.Path.Combine(System.IO.Directory.GetCurrentDirectory(), "multipage.tif"));
// dispose the acquired image
e.Image.Dispose();
}
/// <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)
{
Vintasoft.Twain.Device device = (Vintasoft.Twain.Device)sender;
// unsubscribe from device events
UnsubscribeFromDeviceEvents(device);
// if device is not closed
if (device.State != Vintasoft.Twain.DeviceState.Closed)
// close the device
device.Close();
System.Console.WriteLine("Scan is finished.");
_isScanningFinished = true;
}
/// <summary>
/// Subscribes to the device events.
/// </summary>
private static void SubscribeToDeviceEvents(Vintasoft.Twain.Device device)
{
device.ImageAcquiringProgress += new System.EventHandler<Vintasoft.Twain.ImageAcquiringProgressEventArgs>(device_ImageAcquiringProgress);
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.ImageAcquiringProgress -= new System.EventHandler<Vintasoft.Twain.ImageAcquiringProgressEventArgs>(device_ImageAcquiringProgress);
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);
}
Shared _isScanningFinished As Boolean
''' <summary>
''' Asynchronously acquires images from TWAIN device.
''' </summary>
Public Shared Sub AsynchronouslyAcquireImageFromTwainDevice()
_isScanningFinished = 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 System.ApplicationException(String.Format("Device '{0}' is not found.", deviceName))
End If
' subscribe to device events
SubscribeToDeviceEvents(device)
' disable device UI
device.ShowUI = False
' set Memory transfer mode
device.TransferMode = Vintasoft.Twain.TransferMode.Memory
' open the device
device.Open()
' specify that black-white images must be acquired
device.PixelType = Vintasoft.Twain.PixelType.BW
' specify the threshold for acquired images
device.Threshold = 128
' set the inches as unit of measure
device.UnitOfMeasure = Vintasoft.Twain.UnitOfMeasure.Inches
device.Resolution = New Vintasoft.Twain.Resolution(300F, 300F)
' run asynchronous image acqusition
device.Acquire()
' wait while feeder will be stopped
While Not _isScanningFinished
System.Windows.Forms.Application.DoEvents()
End While
' unsubscribe from device events
UnsubscribeFromDeviceEvents(device)
' close the device
device.Close()
End Using
End Sub
''' <summary>
''' Image acquisition is in progress.
''' </summary>
Private Shared Sub device_ImageAcquiringProgress(sender As Object, e As Vintasoft.Twain.ImageAcquiringProgressEventArgs)
' update progress bar
End Sub
''' <summary>
''' Image is acquired.
''' </summary>
Private Shared Sub device_ImageAcquired(sender As Object, e As Vintasoft.Twain.ImageAcquiredEventArgs)
' add the acquired image to a TIFF file
e.Image.Save(System.IO.Path.Combine(System.IO.Directory.GetCurrentDirectory(), "multipage.tif"))
' dispose the acquired image
e.Image.Dispose()
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)
Dim device As Vintasoft.Twain.Device = DirectCast(sender, Vintasoft.Twain.Device)
' unsubscribe from device events
UnsubscribeFromDeviceEvents(device)
' if device is not closed
If device.State <> Vintasoft.Twain.DeviceState.Closed Then
' close the device
device.Close()
End If
System.Console.WriteLine("Scan is finished.")
_isScanningFinished = True
End Sub
''' <summary>
''' Subscribes to the device events.
''' </summary>
Private Shared Sub SubscribeToDeviceEvents(device As Vintasoft.Twain.Device)
AddHandler device.ImageAcquiringProgress, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiringProgressEventArgs)(AddressOf device_ImageAcquiringProgress)
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.ImageAcquiringProgress, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiringProgressEventArgs)(AddressOf device_ImageAcquiringProgress)
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