Added possibility to handle transferred data by app in another thread for high-speed scanner use.

samples/WinForm32/Form1.Designer.cs

@@ -41,6 +41,7 @@
       lblState = new System.Windows.Forms.Label();
       label3 = new System.Windows.Forms.Label();
       btnOpenDef = new System.Windows.Forms.Button();
+      ckShowUI = new System.Windows.Forms.CheckBox();
       capListView = new System.Windows.Forms.ListView();
       colCap = new System.Windows.Forms.ColumnHeader();
       colType = new System.Windows.Forms.ColumnHeader();
@@ -52,7 +53,7 @@
       btnStart = new System.Windows.Forms.Button();
       btnShowSettings = new System.Windows.Forms.Button();
       btnClose = new System.Windows.Forms.Button();
-      ckShowUI = new System.Windows.Forms.CheckBox();
+      ckBgImageHandling = new System.Windows.Forms.CheckBox();
       ((System.ComponentModel.ISupportInitialize)splitContainer1).BeginInit();
       splitContainer1.Panel1.SuspendLayout();
       splitContainer1.Panel2.SuspendLayout();
@@ -167,6 +168,7 @@
       // 
       // splitContainer1.Panel2
       // 
+      splitContainer1.Panel2.Controls.Add(ckBgImageHandling);
       splitContainer1.Panel2.Controls.Add(ckShowUI);
       splitContainer1.Panel2.Controls.Add(capListView);
       splitContainer1.Panel2.Controls.Add(label4);
@@ -207,6 +209,18 @@
       btnOpenDef.UseVisualStyleBackColor = true;
       btnOpenDef.Click += btnOpenDef_Click;
       // 
+      // ckShowUI
+      // 
+      ckShowUI.AutoSize = true;
+      ckShowUI.Checked = true;
+      ckShowUI.CheckState = System.Windows.Forms.CheckState.Checked;
+      ckShowUI.Location = new System.Drawing.Point(437, 35);
+      ckShowUI.Name = "ckShowUI";
+      ckShowUI.Size = new System.Drawing.Size(69, 19);
+      ckShowUI.TabIndex = 9;
+      ckShowUI.Text = "Show UI";
+      ckShowUI.UseVisualStyleBackColor = true;
+      // 
       // capListView
       // 
       capListView.Anchor = System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Left | System.Windows.Forms.AnchorStyles.Right;
@@ -289,17 +303,17 @@
       btnClose.UseVisualStyleBackColor = true;
       btnClose.Click += btnClose_Click;
       // 
-      // ckShowUI
+      // ckBgImageHandling
       // 
-      ckShowUI.AutoSize = true;
-      ckShowUI.Checked = true;
-      ckShowUI.CheckState = System.Windows.Forms.CheckState.Checked;
-      ckShowUI.Location = new System.Drawing.Point(437, 35);
-      ckShowUI.Name = "ckShowUI";
-      ckShowUI.Size = new System.Drawing.Size(69, 19);
-      ckShowUI.TabIndex = 9;
-      ckShowUI.Text = "Show UI";
-      ckShowUI.UseVisualStyleBackColor = true;
+      ckBgImageHandling.AutoSize = true;
+      ckBgImageHandling.Checked = true;
+      ckBgImageHandling.CheckState = System.Windows.Forms.CheckState.Checked;
+      ckBgImageHandling.Location = new System.Drawing.Point(512, 35);
+      ckBgImageHandling.Name = "ckBgImageHandling";
+      ckBgImageHandling.Size = new System.Drawing.Size(220, 19);
+      ckBgImageHandling.TabIndex = 10;
+      ckBgImageHandling.Text = "Handle image data in another thread";
+      ckBgImageHandling.UseVisualStyleBackColor = true;
       // 
       // Form1
       // 
@@ -345,5 +359,6 @@
     private System.Windows.Forms.ColumnHeader colSupport;
     private System.Windows.Forms.ColumnHeader colExtended;
     private System.Windows.Forms.CheckBox ckShowUI;
+    private System.Windows.Forms.CheckBox ckBgImageHandling;
   }
 }

samples/WinForm32/Form1.cs

@@ -6,12 +6,11 @@ using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Drawing;
-using System.Drawing.Imaging;
 using System.IO;
 using System.Linq;
 using System.Reflection;
-using System.Runtime.Versioning;
 using System.Threading;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 
 namespace WinFormSample
@@ -20,6 +19,8 @@ namespace WinFormSample
   {
     private TwainAppSession twain;
     private readonly string saveFolder;
+    readonly Stopwatch watch = new();
+    private bool _useThreadForImag;
 
     public Form1()
     {
@@ -33,8 +34,9 @@ namespace WinFormSample
       twain.StateChanged += Twain_StateChanged;
       twain.DefaultSourceChanged += Twain_DefaultSourceChanged;
       twain.CurrentSourceChanged += Twain_CurrentSourceChanged;
+      twain.SourceDisabled += Twain_SourceDisabled;
       twain.TransferReady += Twain_TransferReady;
-      twain.Transferred += Twain_DataTransferred;
+      twain.Transferred += Twain_Transferred;
       twain.TransferError += Twain_TransferError;
       twain.DeviceEvent += Twain_DeviceEvent;
 
@@ -47,6 +49,15 @@ namespace WinFormSample
       this.Disposed += Form1_Disposed;
     }
 
+    private void Twain_SourceDisabled(TwainAppSession sender, TW_IDENTITY_LEGACY e)
+    {
+      if (watch.IsRunning)
+      {
+        watch.Stop();
+        MessageBox.Show($"Took {watch.Elapsed} to finish that transfer.");
+      }
+    }
+
     private void SystemEvents_SessionSwitch(object sender, SessionSwitchEventArgs e)
     {
       switch (e.Reason)
@@ -103,28 +114,54 @@ namespace WinFormSample
 
     }
 
-    private void Twain_DataTransferred(TwainAppSession sender, TransferredEventArgs e)
+    private void Twain_Transferred(TwainAppSession sender, TransferredEventArgs e)
     {
       Debug.WriteLine($"[thread {Environment.CurrentManagedThreadId}] data transferred with info {e.ImageInfo}");
-      if (e.Data == null) return;
+      // if using a high-speed scanner, imaging handling could be a bottleneck
+      // so it's possible to pass the data to another thread while the scanning
+      // loop happens. Just remember to dispose it after.
 
-      // example of using some lib to handle image data
-      var saveFile = Path.Combine(saveFolder, (DateTime.Now.Ticks / 1000).ToString());
-      using (var img = new ImageMagick.MagickImage(e.Data))
+      if (_useThreadForImag)
       {
-        if (img.ColorType == ImageMagick.ColorType.Palette)
+        // bad thread example but whatev. should use a dedicated thread of some sort for real
+        Task.Run(() =>
         {
-          // bw or gray
-          saveFile += ".png";
-        }
-        else
+          HandleTransferredData(e);
+        });
+      }
+      else
+      {
+        HandleTransferredData(e);
+      }
+    }
+
+    private void HandleTransferredData(TransferredEventArgs e)
+    {
+      try
+      {
+        // example of using some lib to handle image data
+        var saveFile = Path.Combine(saveFolder, (DateTime.Now.Ticks / 1000).ToString());
+        using (var img = new ImageMagick.MagickImage(e.Data))
         {
-          // color
-          saveFile += ".jpg";
-          img.Quality = 75;
+          if (img.ColorType == ImageMagick.ColorType.Palette)
+          {
+            // bw or gray
+            saveFile += ".png";
+          }
+          else
+          {
+            // color
+            saveFile += ".jpg";
+            img.Quality = 75;
+          }
+          img.Write(saveFile);
+          Debug.WriteLine($"Saved image to {saveFile}");
         }
-        img.Write(saveFile);
-        Debug.WriteLine($"Saved image to {saveFile}");
+      }
+      catch { }
+      finally
+      {
+        e.Dispose();
       }
     }
 
@@ -362,7 +399,11 @@ namespace WinFormSample
 
     private void btnStart_Click(object sender, EventArgs e)
     {
-      twain.EnableSource(ckShowUI.Checked, false);
+      if (twain.EnableSource(ckShowUI.Checked, false).IsSuccess)
+      {
+        _useThreadForImag = ckBgImageHandling.Checked;
+        watch.Restart();
+      }
     }
   }
 }