Here is what we are doing to run scanning in a background thread and poll for the scanning status in small intervals. Below code works inconsistently, when it fails last twain status returned from the Scanner is TwainStatus.TWAIN_SOURCE_ENABLED.
BackgroundWorker code, which calls Acquire(), and GetStatus() functions from DoWork thread. Acquire() function is called from a new Thread started inside BackgroundWorker thread, so that BackgroundWorker's worker thread can poll for the Scanner status at repeated intervals and update the UI.
I have sent an email to esupport (at) gdpicture (dot) com having the sample application attached which reproduces the problem; this may help you to figure out and narrow down the problem.
Regards
Anwar
Code: Select all
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Threading;
using GdPicture;
namespace SampleScanTool
{
public partial class Form1 : Form
{
GdPicture.GdPictureImaging _gdPictureImaging = new GdPicture.GdPictureImaging();
public Form1()
{
InitializeComponent();
_gdPictureImaging.SetLicenseNumber("XXXXXXXXXXXXXXXX");
}
private void button1_Click(object sender, EventArgs e)
{
using (BackgroundWorker _worker = new BackgroundWorker())
{
var errorMessage = string.Empty;
lblStatus.Text = GetStatus();
_worker.WorkerSupportsCancellation = true;
_worker.WorkerReportsProgress = true;
_worker.DoWork += (s, ev) =>
{
// Create a new thread and Scan documents
Thread t = new Thread(() =>
{
try
{
ev.Result = Acquire();
}
catch (Exception ex)
{
_worker.ReportProgress(0, ex.Message);
}
});
t.Start();
// Poll for the status of Scanner in 1000ms intervals
for (int i = 0; i < 1000; i++)
{
Thread.Sleep(500);
if (t.ThreadState == ThreadState.Stopped)
{
_worker.ReportProgress(0, "Scan job completed");
break;
}
if (t.ThreadState == ThreadState.Running)
{
_worker.ReportProgress(0, GetStatus()); // Get status of Scanner
}
}
};
_worker.RunWorkerCompleted += (s, ev) =>
{
if (!ev.Cancelled && errorMessage == string.Empty)
{
if (ev.Result != null)
{
// handle result stream here
}
}
else
{
if (errorMessage != string.Empty)
{
}
}
};
_worker.ProgressChanged += (s, ev) =>
{
lblStatus.Text = ev.UserState.ToString();
};
_worker.RunWorkerAsync();
}
}
private Stream Acquire()
{
int imageId = 0;
var file = Stream.Null; // Stream to save scanned document
try
{
_gdPictureImaging.TwainSelectSource(IntPtr.Zero);
if (_gdPictureImaging.TwainOpenDefaultSource(IntPtr.Zero))
{
_gdPictureImaging.TwainSetHideUI(true);
_gdPictureImaging.TwainSetIndicators(false);
imageId = _gdPictureImaging.TwainAcquireToGdPictureImage(IntPtr.Zero); // Acquire image
if (imageId != 0)
{
file = new MemoryStream();
_gdPictureImaging.SaveAsPDFStream(imageId, ref file, false, "", "", "", "", ""); // Save to Stream
_gdPictureImaging.ReleaseGdPictureImage(imageId);
MessageBox.Show("Image Acquired");
}
else
{
throw new ApplicationException("Failed to scan the document");
}
_gdPictureImaging.TwainUnloadSourceManager(IntPtr.Zero); // Close source
_gdPictureImaging.TwainCloseSource();
return file;
}
else
{
throw new ApplicationException("Failed to open scanner source");
}
}
catch (Exception)
{
throw; // rethrow exception to the UI
}
}
private string GetStatus()
{
var statusMessage = String.Empty;
try
{
var status = _gdPictureImaging.TwainGetState();
switch (status)
{
case TwainStatus.TWAIN_ERROR:
statusMessage = "Could not communicate with the scanner. Please verify that scanner is turned on and connected";
break;
case TwainStatus.TWAIN_PRESESSION:
statusMessage = "Scan tool is initializing and preparing to communicate with the scanner";
break;
case TwainStatus.TWAIN_SM_LOADED:
statusMessage = "Scan tool related system files have been loaded";
break;
case TwainStatus.TWAIN_SM_OPEN:
statusMessage = "Scan tool is checking for the available scanners";
break;
case TwainStatus.TWAIN_SOURCE_ENABLED:
statusMessage = "Scanner is working";
break;
case TwainStatus.TWAIN_SOURCE_OPEN:
statusMessage = "Scan tool is communicating to the scanner";
break;
case TwainStatus.TWAIN_TRANSFER_READY:
statusMessage = "Scan tool has detected that files are ready for transfer";
break;
case TwainStatus.TWAIN_TRANSFERRING:
statusMessage = "Scanner is transferring the scanned images";
break;
};
return statusMessage;
}
catch (Exception)
{
throw;
}
}
}
}
