Some more QoL and sample process options.

samples/WinForm32/Form1.Designer.cs

@@ -41,6 +41,9 @@
       lblState = new System.Windows.Forms.Label();
       label3 = new System.Windows.Forms.Label();
       btnOpenDef = new System.Windows.Forms.Button();
+      btnOpenFolder = new System.Windows.Forms.Button();
+      ckSystemDrawing = new System.Windows.Forms.CheckBox();
+      ckBgImageHandling = new System.Windows.Forms.CheckBox();
       ckShowUI = new System.Windows.Forms.CheckBox();
       capListView = new System.Windows.Forms.ListView();
       colCap = new System.Windows.Forms.ColumnHeader();
@@ -53,7 +56,7 @@
       btnStart = new System.Windows.Forms.Button();
       btnShowSettings = new System.Windows.Forms.Button();
       btnClose = new System.Windows.Forms.Button();
-      ckBgImageHandling = new System.Windows.Forms.CheckBox();
+      ckSaveDisk = new System.Windows.Forms.CheckBox();
       ((System.ComponentModel.ISupportInitialize)splitContainer1).BeginInit();
       splitContainer1.Panel1.SuspendLayout();
       splitContainer1.Panel2.SuspendLayout();
@@ -168,6 +171,9 @@
       // 
       // splitContainer1.Panel2
       // 
+      splitContainer1.Panel2.Controls.Add(ckSaveDisk);
+      splitContainer1.Panel2.Controls.Add(btnOpenFolder);
+      splitContainer1.Panel2.Controls.Add(ckSystemDrawing);
       splitContainer1.Panel2.Controls.Add(ckBgImageHandling);
       splitContainer1.Panel2.Controls.Add(ckShowUI);
       splitContainer1.Panel2.Controls.Add(capListView);
@@ -209,6 +215,38 @@
       btnOpenDef.UseVisualStyleBackColor = true;
       btnOpenDef.Click += btnOpenDef_Click;
       // 
+      // btnOpenFolder
+      // 
+      btnOpenFolder.Location = new System.Drawing.Point(512, 106);
+      btnOpenFolder.Name = "btnOpenFolder";
+      btnOpenFolder.Size = new System.Drawing.Size(147, 23);
+      btnOpenFolder.TabIndex = 13;
+      btnOpenFolder.Text = "Open saved folder";
+      btnOpenFolder.UseVisualStyleBackColor = true;
+      btnOpenFolder.Click += btnOpenFolder_Click;
+      // 
+      // ckSystemDrawing
+      // 
+      ckSystemDrawing.AutoSize = true;
+      ckSystemDrawing.Location = new System.Drawing.Point(512, 58);
+      ckSystemDrawing.Name = "ckSystemDrawing";
+      ckSystemDrawing.Size = new System.Drawing.Size(209, 19);
+      ckSystemDrawing.TabIndex = 11;
+      ckSystemDrawing.Text = "Use System.Drawing to save image";
+      ckSystemDrawing.UseVisualStyleBackColor = true;
+      // 
+      // ckBgImageHandling
+      // 
+      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;
+      // 
       // ckShowUI
       // 
       ckShowUI.AutoSize = true;
@@ -226,10 +264,10 @@
       capListView.Anchor = System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Left | System.Windows.Forms.AnchorStyles.Right;
       capListView.Columns.AddRange(new System.Windows.Forms.ColumnHeader[] { colCap, colType, colCur, colDef, colExtended, colSupport });
       capListView.FullRowSelect = true;
-      capListView.Location = new System.Drawing.Point(11, 87);
+      capListView.Location = new System.Drawing.Point(11, 135);
       capListView.MultiSelect = false;
       capListView.Name = "capListView";
-      capListView.Size = new System.Drawing.Size(771, 462);
+      capListView.Size = new System.Drawing.Size(771, 414);
       capListView.TabIndex = 8;
       capListView.UseCompatibleStateImageBehavior = false;
       capListView.View = System.Windows.Forms.View.Details;
@@ -267,7 +305,7 @@
       // label4
       // 
       label4.AutoSize = true;
-      label4.Location = new System.Drawing.Point(13, 62);
+      label4.Location = new System.Drawing.Point(11, 110);
       label4.Name = "label4";
       label4.Size = new System.Drawing.Size(91, 15);
       label4.TabIndex = 7;
@@ -303,17 +341,15 @@
       btnClose.UseVisualStyleBackColor = true;
       btnClose.Click += btnClose_Click;
       // 
-      // ckBgImageHandling
+      // ckSaveDisk
       // 
-      ckBgImageHandling.AutoSize = true;
+      ckSaveDisk.AutoSize = true;
-      ckBgImageHandling.Checked = true;
+      ckSaveDisk.Location = new System.Drawing.Point(512, 83);
-      ckBgImageHandling.CheckState = System.Windows.Forms.CheckState.Checked;
+      ckSaveDisk.Name = "ckSaveDisk";
-      ckBgImageHandling.Location = new System.Drawing.Point(512, 35);
+      ckSaveDisk.Size = new System.Drawing.Size(88, 19);
-      ckBgImageHandling.Name = "ckBgImageHandling";
+      ckSaveDisk.TabIndex = 12;
-      ckBgImageHandling.Size = new System.Drawing.Size(220, 19);
+      ckSaveDisk.Text = "Save to disk";
-      ckBgImageHandling.TabIndex = 10;
+      ckSaveDisk.UseVisualStyleBackColor = true;
-      ckBgImageHandling.Text = "Handle image data in another thread";
-      ckBgImageHandling.UseVisualStyleBackColor = true;
       // 
       // Form1
       // 
@@ -360,5 +396,8 @@
     private System.Windows.Forms.ColumnHeader colExtended;
     private System.Windows.Forms.CheckBox ckShowUI;
     private System.Windows.Forms.CheckBox ckBgImageHandling;
+    private System.Windows.Forms.CheckBox ckSystemDrawing;
+    private System.Windows.Forms.Button btnOpenFolder;
+    private System.Windows.Forms.CheckBox ckSaveDisk;
   }
 }

samples/WinForm32/Form1.cs

@@ -6,6 +6,7 @@ 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;
@@ -17,10 +18,15 @@ namespace WinFormSample
 {
   public partial class Form1 : Form
   {
-    private TwainAppSession twain;
+    TwainAppSession twain;
-    private readonly string saveFolder;
+    readonly string saveFolder;
     readonly Stopwatch watch = new();
-    private bool _useThreadForImag;
+    readonly ImageCodecInfo _jpegEncoder;
+    readonly EncoderParameters _jpegParameters;
+    readonly int _jpegQuality = 75;
+    bool _useThreadForImag;
+    bool _useSystemDrawing;
+    bool _saveDisk;
 
     public Form1()
     {
@@ -43,10 +49,15 @@ namespace WinFormSample
       capListView.SetDoubleBufferedAsNeeded();
       SystemEvents.SessionSwitch += SystemEvents_SessionSwitch;
 
-      saveFolder = Path.Combine(Path.GetTempPath(), "ntwain-sample");
+      saveFolder = Path.Combine(Path.GetTempPath(), "ntwain-sample" + Path.DirectorySeparatorChar);
       Directory.CreateDirectory(saveFolder);
 
       this.Disposed += Form1_Disposed;
+
+
+      _jpegParameters = new EncoderParameters(1);
+      _jpegParameters.Param[0] = new EncoderParameter(Encoder.Quality, (long)_jpegQuality);
+      _jpegEncoder = ImageCodecInfo.GetImageEncoders().First(enc => enc.FormatID == ImageFormat.Jpeg.Guid);
     }
 
     private void Twain_SourceDisabled(TwainAppSession sender, TW_IDENTITY_LEGACY e)
@@ -137,31 +148,62 @@ namespace WinFormSample
 
     private void HandleTransferredData(TransferredEventArgs e)
     {
-      try
+      if (e.Data != null)
       {
-        // example of using some lib to handle image data
+        try
-        var saveFile = Path.Combine(saveFolder, (DateTime.Now.Ticks / 1000).ToString());
-        using (var img = new ImageMagick.MagickImage(e.Data))
         {
-          if (img.ColorType == ImageMagick.ColorType.Palette)
+          // example of using some lib to handle image data
+          var saveFile = Path.Combine(saveFolder, (DateTime.Now.Ticks / 1000).ToString());
+
+          if (_useSystemDrawing)
           {
-            // bw or gray
+            using (var img = Image.FromStream(e.Data.AsStream()))
-            saveFile += ".png";
+            {
+              if (img.PixelFormat == System.Drawing.Imaging.PixelFormat.Format1bppIndexed ||
+                img.PixelFormat == System.Drawing.Imaging.PixelFormat.Format8bppIndexed)
+              {
+                // bw or gray
+                saveFile += ".png";
+                if (_saveDisk) img.Save(saveFile, ImageFormat.Png);
+                else img.Save(new NoOpStream(), ImageFormat.Png);
+              }
+              else
+              {
+                // color
+                saveFile += ".jpg";
+                if (_saveDisk) img.Save(saveFile, _jpegEncoder, _jpegParameters);
+                else img.Save(new NoOpStream(), _jpegEncoder, _jpegParameters);
+              }
+            }
           }
           else
           {
-            // color
+            using (var img = new ImageMagick.MagickImage(e.Data.AsSpan()))
-            saveFile += ".jpg";
+            {
-            img.Quality = 75;
+              var format = ImageMagick.MagickFormat.Png;
+              if (img.ColorType == ImageMagick.ColorType.Palette)
+              {
+                // bw or gray
+                saveFile += ".png";
+              }
+              else
+              {
+                // color
+                saveFile += ".jpg";
+                format = ImageMagick.MagickFormat.Jpeg;
+                img.Quality = _jpegQuality;
+              }
+              if (_saveDisk) img.Write(saveFile);
+              else img.Write(new NoOpStream(), format);
+            }
+            Debug.WriteLine($"Saved image to {saveFile}");
           }
-          img.Write(saveFile);
-          Debug.WriteLine($"Saved image to {saveFile}");
         }
-      }
+        catch { }
-      catch { }
+        finally
-      finally
+        {
-      {
+          e.Dispose();
-        e.Dispose();
+        }
       }
     }
 
@@ -402,8 +444,20 @@ namespace WinFormSample
       if (twain.EnableSource(ckShowUI.Checked, false).IsSuccess)
       {
         _useThreadForImag = ckBgImageHandling.Checked;
+        _useSystemDrawing = ckSystemDrawing.Checked;
+        _saveDisk = ckSaveDisk.Checked;
         watch.Restart();
       }
     }
+
+    private void btnOpenFolder_Click(object sender, EventArgs e)
+    {
+      try
+      {
+        if (!Directory.Exists(saveFolder)) Directory.CreateDirectory(saveFolder);
+        using (Process.Start(new ProcessStartInfo { FileName = saveFolder, UseShellExecute = true })) { }
+      }
+      catch { }
+    }
   }
 }

samples/WinForm32/NoOpStream.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace WinFormSample
+{
+  internal class NoOpStream : Stream
+  {
+    public override bool CanRead => false;
+
+    public override bool CanSeek => false;
+
+    public override bool CanWrite => true;
+
+    public override long Length => 0;
+
+    public override long Position { get => 0; set { } }
+
+    public override void Flush()
+    {
+    }
+
+    public override int Read(byte[] buffer, int offset, int count)
+    {
+      throw new NotImplementedException();
+    }
+
+    public override long Seek(long offset, SeekOrigin origin)
+    {
+      throw new NotImplementedException();
+    }
+
+    public override void SetLength(long value)
+    {
+    }
+
+    public override void Write(byte[] buffer, int offset, int count)
+    {
+    }
+  }
+}

src/NTwain/Data/BufferedData.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Buffers;
+using System.IO;
 
 namespace NTwain.Data
 {
@@ -13,7 +14,7 @@ namespace NTwain.Data
     // so the array max is made with 32 MB. Typical usage should be a lot less.
     internal static readonly ArrayPool<byte> MemPool = ArrayPool<byte>.Create(32 * 1024 * 1024, 8);
 
-    public BufferedData(int size)
+    internal BufferedData(int size)
     {
       _buffer = MemPool.Rent(size);
       _length = size;
@@ -27,14 +28,14 @@ namespace NTwain.Data
       _fromPool = fromPool;
     }
 
+    bool _disposed;
     bool _fromPool;
 
     /// <summary>
     /// Bytes buffer. This may be bigger than the data size
     /// and contain invalid data.
     /// </summary>
-    byte[]? _buffer;
+    byte[] _buffer;
-    public byte[]? Buffer { get; }
 
     /// <summary>
     /// Actual usable data length in the buffer.
@@ -45,19 +46,47 @@ namespace NTwain.Data
     /// As a span of usable data.
     /// </summary>
     /// <returns></returns>
+    /// <exception cref="ObjectDisposedException"></exception>
     public ReadOnlySpan<byte> AsSpan()
     {
-      if (_buffer != null) return _buffer.AsSpan(0, _length);
+      if (_disposed) throw new ObjectDisposedException(GetType().FullName);
-      return Span<byte>.Empty;
+      return _buffer.AsSpan(0, _length);
+    }
+
+    /// <summary>
+    /// As a span of usable data.
+    /// </summary>
+    /// <returns></returns>
+    /// <exception cref="ObjectDisposedException"></exception>
+    public ReadOnlyMemory<byte> AsMemory()
+    {
+      if (_disposed) throw new ObjectDisposedException(GetType().FullName);
+      return _buffer.AsMemory(0, _length);
+    }
+
+    /// <summary>
+    /// As a readonly stream.
+    /// </summary>
+    /// <returns></returns>
+    /// <exception cref="ObjectDisposedException"></exception>
+    public Stream AsStream()
+    {
+      if (_disposed) throw new ObjectDisposedException(GetType().FullName);
+      return new MemoryStream(_buffer, 0, _length, false);
     }
 
     public void Dispose()
     {
-      if (_fromPool && _buffer != null)
+      if (_fromPool && _disposed)
       {
         MemPool.Return(_buffer);
-        _buffer = null;
+        _disposed = true;
       }
     }
+
+    public static implicit operator ReadOnlySpan<byte>(BufferedData value) => value.AsSpan();
+    public static implicit operator ReadOnlyMemory<byte>(BufferedData value) => value.AsMemory();
+    public static implicit operator Stream(BufferedData value) => value.AsStream();
+
   }
 }

src/NTwain/TransferredEventArgs.cs

@@ -39,7 +39,7 @@ namespace NTwain
     /// IMPORTANT: Content of this array will not be valid once
     /// this event arg has been disposed.
     /// </summary>
-    public ReadOnlySpan<byte> Data => _data == null ? ReadOnlySpan<byte>.Empty : _data.AsSpan();
+    public BufferedData? Data => _data;
 
     /// <summary>
     /// The file info if the transfer involved file information.