[FileExplorerAddOns]Improves handling of Gcode Thumbnails (#27947)

* Improves handling of Gcode Thumbnails

* Remove Peek support

* Moves GcodeHelper to PreviewHandlerCommon

* Reverts minor change

* Skip unknown data on GcodeHelper.GetBestThumbnail

* Replaces QOI.Core with QoiImage

* Fixes spellchecker

* Reverts changes to NOTICE.md

* Minor QoiImage improvements

* Use custom QoiPixel struct

* Add MIT notice for the QOI reference code

* Fix spellcheck for the MIT notice

* Update NOTICE.md

tweaked notice a bit

.github/actions/spell-check/allow/names.txt

@@ -35,6 +35,7 @@ mshtang
 Myrvold
 naveensrinivasan
 nVidia
+phoboslab
 Ponten
 Pooja
 robmen
@@ -44,6 +45,7 @@ skycommand
 snickler
 sinclairinat
 streamjsonrpc
+Szablewski
 tilovell
 TheJoeFin
 Triet

.github/actions/spell-check/expect.txt

@@ -1014,6 +1014,7 @@ lstrlen
 LTRB
 LTRREADING
 luid
+LUMA
 lusrmgr
 LVal
 LWA
@@ -1496,6 +1497,7 @@ qianlifeng
 qit
 QITAB
 QITABENT
+qoi
 qps
 Quarternary
 QUERYENDSESSION
@@ -2250,6 +2252,7 @@ xsi
 XStr
 XUP
 XVIRTUALSCREEN
+xxxxxx
 YAxis
 ycv
 Yeet

NOTICE.md

@@ -67,6 +67,34 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 
+### The Quite OK Image Format reference decoder
+
+**Source**: https://github.com/phoboslab/qoi
+
+**Note**: [@pedrolamas](https://github.com/pedrolamas) translated and adapted the reference decoder code to C# that is in PowerToys from the original C++ implementation.
+
+MIT License
+
+Copyright (c) 2022 Dominic Szablewski
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
 ## Utility: ImageResizer
 
 ### Brice Lams's Image Resizer License

src/modules/previewpane/GcodePreviewHandler/GcodePreviewHandlerControl.cs

@@ -2,14 +2,6 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
-using System.Drawing;
-using System.IO;
-using System.Linq;
-using System.Runtime.InteropServices.ComTypes;
-using System.Text;
-using System.Windows.Forms;
 using Common;
 using Common.Utilities;
 using Microsoft.PowerToys.PreviewHandler.Gcode.Telemetry.Events;
@@ -67,7 +59,9 @@ namespace Microsoft.PowerToys.PreviewHandler.Gcode
 
                 using (var reader = new StreamReader(fs))
                 {
-                    thumbnail = GetThumbnail(reader);
+                    var gcodeThumbnail = GcodeHelper.GetBestThumbnail(reader);
+
+                    thumbnail = gcodeThumbnail?.GetBitmap();
                 }
 
                 _infoBarAdded = false;
@@ -92,66 +86,6 @@ namespace Microsoft.PowerToys.PreviewHandler.Gcode
             }
         }
 
-        /// <summary>
-        /// Reads the G-code content searching for thumbnails and returns the largest.
-        /// </summary>
-        /// <param name="reader">The TextReader instance for the G-code content.</param>
-        /// <returns>A thumbnail extracted from the G-code content.</returns>
-        public static Bitmap GetThumbnail(TextReader reader)
-        {
-            if (reader == null)
-            {
-                return null;
-            }
-
-            Bitmap thumbnail = null;
-
-            var bitmapBase64 = GetBase64Thumbnails(reader)
-                .OrderByDescending(x => x.Length)
-                .FirstOrDefault();
-
-            if (!string.IsNullOrEmpty(bitmapBase64))
-            {
-                var bitmapBytes = Convert.FromBase64String(bitmapBase64);
-
-                thumbnail = new Bitmap(new MemoryStream(bitmapBytes));
-            }
-
-            return thumbnail;
-        }
-
-        /// <summary>
-        /// Gets all thumbnails in base64 format found on the G-code data.
-        /// </summary>
-        /// <param name="reader">The TextReader instance for the G-code content.</param>
-        /// <returns>An enumeration of thumbnails in base64 format found on the G-code.</returns>
-        private static IEnumerable<string> GetBase64Thumbnails(TextReader reader)
-        {
-            string line;
-            StringBuilder capturedText = null;
-
-            while ((line = reader.ReadLine()) != null)
-            {
-                if (line.StartsWith("; thumbnail begin", StringComparison.InvariantCulture))
-                {
-                    capturedText = new StringBuilder();
-                }
-                else if (line == "; thumbnail end")
-                {
-                    if (capturedText != null)
-                    {
-                        yield return capturedText.ToString();
-
-                        capturedText = null;
-                    }
-                }
-                else if (capturedText != null)
-                {
-                    capturedText.Append(line[2..]);
-                }
-            }
-        }
-
         /// <summary>
         /// Occurs when RichtextBox is resized.
         /// </summary>

src/modules/previewpane/GcodeThumbnailProvider/GcodeThumbnailProvider.cs

@@ -2,7 +2,7 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 using System.Drawing.Drawing2D;
-using System.Text;
+using Common.Utilities;
 
 namespace Microsoft.PowerToys.ThumbnailHandler.Gcode
 {
@@ -45,64 +45,23 @@ namespace Microsoft.PowerToys.ThumbnailHandler.Gcode
                 return null;
             }
 
-            Bitmap thumbnail = null;
+            var gcodeThumbnail = GcodeHelper.GetBestThumbnail(reader);
 
-            var bitmapBase64 = GetBase64Thumbnails(reader)
-                .OrderByDescending(x => x.Length)
-                .FirstOrDefault();
+            var thumbnail = gcodeThumbnail?.GetBitmap();
 
-            if (!string.IsNullOrEmpty(bitmapBase64))
+            if (thumbnail != null && thumbnail.Width != cx && thumbnail.Height != cx)
             {
-                var bitmapBytes = Convert.FromBase64String(bitmapBase64);
-
-                thumbnail = new Bitmap(new MemoryStream(bitmapBytes));
-
-                if (thumbnail.Width != cx && thumbnail.Height != cx)
-                {
-                    // We are not the appropriate size for caller.  Resize now while
-                    // respecting the aspect ratio.
-                    float scale = Math.Min((float)cx / thumbnail.Width, (float)cx / thumbnail.Height);
-                    int scaleWidth = (int)(thumbnail.Width * scale);
-                    int scaleHeight = (int)(thumbnail.Height * scale);
-                    thumbnail = ResizeImage(thumbnail, scaleWidth, scaleHeight);
-                }
+                // We are not the appropriate size for caller.  Resize now while
+                // respecting the aspect ratio.
+                float scale = Math.Min((float)cx / thumbnail.Width, (float)cx / thumbnail.Height);
+                int scaleWidth = (int)(thumbnail.Width * scale);
+                int scaleHeight = (int)(thumbnail.Height * scale);
+                thumbnail = ResizeImage(thumbnail, scaleWidth, scaleHeight);
             }
 
             return thumbnail;
         }
 
-        /// <summary>
-        /// Gets all thumbnails in base64 format found on the G-code data.
-        /// </summary>
-        /// <param name="reader">The TextReader instance for the G-code content.</param>
-        /// <returns>An enumeration of thumbnails in base64 format found on the G-code.</returns>
-        private static IEnumerable<string> GetBase64Thumbnails(TextReader reader)
-        {
-            string line;
-            StringBuilder capturedText = null;
-
-            while ((line = reader.ReadLine()) != null)
-            {
-                if (line.StartsWith("; thumbnail begin", StringComparison.InvariantCulture))
-                {
-                    capturedText = new StringBuilder();
-                }
-                else if (line == "; thumbnail end")
-                {
-                    if (capturedText != null)
-                    {
-                        yield return capturedText.ToString();
-
-                        capturedText = null;
-                    }
-                }
-                else if (capturedText != null)
-                {
-                    capturedText.Append(line[2..]);
-                }
-            }
-        }
-
         /// <summary>
         /// Resize the image with high quality to the specified width and height.
         /// </summary>

src/modules/previewpane/UnitTests-GcodePreviewHandler/GcodePreviewHandlerTest.cs

@@ -19,14 +19,17 @@ namespace GcodePreviewHandlerUnitTests
     [System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "CA2201:Do not raise reserved exception types", Justification = "new Exception() is fine in test projects.")]
     public class GcodePreviewHandlerTest
     {
-        [TestMethod]
-        public void GcodePreviewHandlerControlAddsControlsToFormWhenDoPreviewIsCalled()
+        [DataTestMethod]
+        [DataRow("HelperFiles/sample.gcode")]
+        [DataRow("HelperFiles/sample_JPG.gcode")]
+        [DataRow("HelperFiles/sample_QOI.gcode")]
+        public void GcodePreviewHandlerControlAddsControlsToFormWhenDoPreviewIsCalled(string filePath)
         {
             // Arrange
             using (var gcodePreviewHandlerControl = new GcodePreviewHandlerControl())
             {
                 // Act
-                var file = File.ReadAllBytes("HelperFiles/sample.gcode");
+                var file = File.ReadAllBytes(filePath);
 
                 gcodePreviewHandlerControl.DoPreview<IStream>(GetMockStream(file));
 

src/modules/previewpane/UnitTests-GcodePreviewHandler/UnitTests-GcodePreviewHandler.csproj

@@ -22,6 +22,8 @@
 
   <ItemGroup>
     <None Remove="HelperFiles\sample.gcode" />
+    <None Remove="HelperFiles\sample_JPG.gcode" />
+    <None Remove="HelperFiles\sample_QOI.gcode" />
   </ItemGroup>
 
   <ItemGroup>
@@ -41,6 +43,12 @@
     <Content Include="HelperFiles\sample.gcode">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </Content>
+    <Content Include="HelperFiles\sample_JPG.gcode">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
+    <Content Include="HelperFiles\sample_QOI.gcode">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
     <Compile Include="..\STATestClassAttribute.cs" Link="STATestClassAttribute.cs" />
     <Compile Include="..\STATestMethodAttribute.cs" Link="STATestMethodAttribute.cs" />
   </ItemGroup>

src/modules/previewpane/UnitTests-GcodeThumbnailProvider/GcodeThumbnailProviderTests.cs

@@ -2,28 +2,24 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Drawing;
 using System.IO;
-using System.Runtime.InteropServices;
-using System.Runtime.InteropServices.ComTypes;
-using Common.ComInterlop;
 using Microsoft.PowerToys.STATestExtension;
 using Microsoft.PowerToys.ThumbnailHandler.Gcode;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
-using Moq;
 
 namespace GcodeThumbnailProviderUnitTests
 {
     [STATestClass]
     public class GcodeThumbnailProviderTests
     {
-        [TestMethod]
-        public void GetThumbnailValidStreamGcode()
+        [DataTestMethod]
+        [DataRow("HelperFiles/sample.gcode")]
+        [DataRow("HelperFiles/sample_JPG.gcode")]
+        [DataRow("HelperFiles/sample_QOI.gcode")]
+        public void GetThumbnailValidStreamGcode(string filePath)
         {
             // Act
-            var filePath = "HelperFiles/sample.gcode";
-
             GcodeThumbnailProvider provider = new GcodeThumbnailProvider(filePath);
 
             Bitmap bitmap = provider.GetThumbnail(256);

src/modules/previewpane/UnitTests-GcodeThumbnailProvider/UnitTests-GcodeThumbnailProvider.csproj

@@ -23,6 +23,8 @@
 
   <ItemGroup>
     <None Remove="HelperFiles\sample.gcode" />
+    <None Remove="HelperFiles\sample_JPG.gcode" />
+    <None Remove="HelperFiles\sample_QOI.gcode" />
   </ItemGroup>
 
   <ItemGroup>
@@ -44,5 +46,11 @@
     <Content Include="HelperFiles\sample.gcode">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </Content>
+    <Content Include="HelperFiles\sample_JPG.gcode">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
+    <Content Include="HelperFiles\sample_QOI.gcode">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </Content>
   </ItemGroup>
 </Project>

src/modules/previewpane/common/PreviewHandlerCommon.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <UseWindowsForms>true</UseWindowsForms>
     <AssemblyTitle>PowerToys.PreviewHandlerCommon</AssemblyTitle>
@@ -9,6 +9,8 @@
     <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
     <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
+    <Nullable>enable</Nullable>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
   <PropertyGroup>

src/modules/previewpane/common/Utilities/GcodeHelper.cs

@@ -0,0 +1,81 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+
+namespace Common.Utilities
+{
+    /// <summary>
+    /// Gcode file helper class.
+    /// </summary>
+    public static class GcodeHelper
+    {
+        /// <summary>
+        /// Gets any thumbnails found in a gcode file.
+        /// </summary>
+        /// <param name="reader">The <see cref="TextReader"/> instance to the gcode file.</param>
+        /// <returns>The thumbnails found in a gcode file.</returns>
+        public static IEnumerable<GcodeThumbnail> GetThumbnails(TextReader reader)
+        {
+            string? line;
+            var format = GcodeThumbnailFormat.Unknown;
+            StringBuilder? capturedText = null;
+
+            while ((line = reader.ReadLine()) != null)
+            {
+                if (line.StartsWith("; thumbnail", StringComparison.InvariantCulture))
+                {
+                    var parts = line[11..].Split(" ");
+
+                    switch (parts[1])
+                    {
+                        case "begin":
+                            format = parts[0].ToUpperInvariant() switch
+                            {
+                                "" => GcodeThumbnailFormat.PNG,
+                                "_JPG" => GcodeThumbnailFormat.JPG,
+                                "_QOI" => GcodeThumbnailFormat.QOI,
+                                _ => GcodeThumbnailFormat.Unknown,
+                            };
+                            capturedText = new StringBuilder();
+
+                            break;
+
+                        case "end":
+                            if (capturedText != null)
+                            {
+                                yield return new GcodeThumbnail(format, capturedText.ToString());
+
+                                capturedText = null;
+                            }
+
+                            break;
+                    }
+                }
+                else
+                {
+                    capturedText?.Append(line[2..]);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets the best thumbnail available in a gcode file.
+        /// </summary>
+        /// <param name="reader">The <see cref="TextReader"/> instance to the gcode file.</param>
+        /// <returns>The best thumbnail available in the gcode file.</returns>
+        public static GcodeThumbnail? GetBestThumbnail(TextReader reader)
+        {
+            return GetThumbnails(reader)
+                .Where(x => x.Format != GcodeThumbnailFormat.Unknown)
+                .OrderByDescending(x => (int)x.Format)
+                .ThenByDescending(x => x.Data.Length)
+                .FirstOrDefault();
+        }
+    }
+}

src/modules/previewpane/common/Utilities/GcodeThumbnail.cs

@@ -0,0 +1,72 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Drawing;
+using System.IO;
+using PreviewHandlerCommon.Utilities;
+
+namespace Common.Utilities
+{
+    /// <summary>
+    /// Represents a gcode thumbnail.
+    /// </summary>
+    public class GcodeThumbnail
+    {
+        /// <summary>
+        /// Gets the gcode thumbnail image format.
+        /// </summary>
+        public GcodeThumbnailFormat Format { get; }
+
+        /// <summary>
+        /// Gets the gcode thumbnail image data in base64.
+        /// </summary>
+        public string Data { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GcodeThumbnail"/> class.
+        /// </summary>
+        /// <param name="format">The gcode thumbnail image format.</param>
+        /// <param name="data">The gcode thumbnail image data in base64.</param>
+        public GcodeThumbnail(GcodeThumbnailFormat format, string data)
+        {
+            Format = format;
+            Data = data;
+        }
+
+        /// <summary>
+        /// Gets a <see cref="Bitmap"/> representing this thumbnail.
+        /// </summary>
+        /// <returns>A <see cref="Bitmap"/> representing this thumbnail.</returns>
+        public Bitmap? GetBitmap()
+        {
+            switch (Format)
+            {
+                case GcodeThumbnailFormat.JPG:
+                case GcodeThumbnailFormat.PNG:
+                    return BitmapFromBase64String();
+
+                case GcodeThumbnailFormat.QOI:
+                    return BitmapFromQoiBase64String();
+
+                default:
+                    return null;
+            }
+        }
+
+        private Bitmap BitmapFromBase64String()
+        {
+            var bitmapBytes = Convert.FromBase64String(Data);
+
+            return new Bitmap(new MemoryStream(bitmapBytes));
+        }
+
+        private Bitmap BitmapFromQoiBase64String()
+        {
+            var bitmapBytes = Convert.FromBase64String(Data);
+
+            return QoiImage.FromStream(new MemoryStream(bitmapBytes));
+        }
+    }
+}

src/modules/previewpane/common/Utilities/GcodeThumbnailFormat.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Utilities
+{
+    /// <summary>
+    /// The gcode thumbnail image format.
+    /// </summary>
+    public enum GcodeThumbnailFormat
+    {
+        /// <summary>
+        /// Unknown image format.
+        /// </summary>
+        Unknown,
+
+        /// <summary>
+        /// JPG image format.
+        /// </summary>
+        JPG,
+
+        /// <summary>
+        /// QOI image format.
+        /// </summary>
+        QOI,
+
+        /// <summary>
+        /// PNG image format.
+        /// </summary>
+        PNG,
+    }
+}

src/modules/previewpane/common/Utilities/QoiImage.cs

@@ -0,0 +1,177 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Buffers.Binary;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.IO;
+
+//// Based on https://github.com/phoboslab/qoi/blob/master/qoi.h
+
+namespace PreviewHandlerCommon.Utilities
+{
+    /// <summary>
+    /// QOI Image helper.
+    /// </summary>
+    public static class QoiImage
+    {
+#pragma warning disable SA1310 // Field names should not contain underscore
+        private const byte QOI_OP_INDEX = 0x00; // 00xxxxxx
+        private const byte QOI_OP_DIFF = 0x40;  // 01xxxxxx
+        private const byte QOI_OP_LUMA = 0x80;  // 10xxxxxx
+        private const byte QOI_OP_RUN = 0xc0;   // 11xxxxxx
+        private const byte QOI_OP_RGB = 0xfe;   // 11111110
+        private const byte QOI_OP_RGBA = 0xff;  // 11111111
+
+        private const byte QOI_MASK_2 = 0xc0;   // 11000000
+
+        private const int QOI_MAGIC = 'q' << 24 | 'o' << 16 | 'i' << 8 | 'f';
+        private const int QOI_HEADER_SIZE = 14;
+
+        private const uint QOI_PIXELS_MAX = 400000000;
+
+        private const byte QOI_PADDING_LENGTH = 8;
+#pragma warning restore SA1310 // Field names should not contain underscore
+
+        private record struct QoiPixel(byte R, byte G, byte B, byte A)
+        {
+            public readonly int GetColorHash() => (R * 3) + (G * 5) + (B * 7) + (A * 11);
+        }
+
+        /// <summary>
+        /// Creates a <see cref="Bitmap"/> from the specified QOI data stream.
+        /// </summary>
+        /// <param name="stream">A <see cref="Stream"/> that contains the QOI data.</param>
+        /// <returns>The <see cref="Bitmap"/> this method creates.</returns>
+        /// <exception cref="ArgumentException">The stream does not have a valid QOI image format.</exception>
+        public static Bitmap FromStream(Stream stream)
+        {
+            var fileSize = stream.Length;
+
+            if (fileSize < QOI_HEADER_SIZE + QOI_PADDING_LENGTH)
+            {
+                throw new ArgumentException("Not enough data for a QOI file");
+            }
+
+            using var reader = new BinaryReader(stream);
+
+            var headerMagic = ReadUInt32BigEndian(reader);
+
+            if (headerMagic != QOI_MAGIC)
+            {
+                throw new ArgumentException("Invalid QOI file header");
+            }
+
+            var width = ReadUInt32BigEndian(reader);
+            var height = ReadUInt32BigEndian(reader);
+            var channels = reader.ReadByte();
+            var colorSpace = reader.ReadByte();
+
+            if (width == 0 || height == 0 || channels < 3 || channels > 4 || colorSpace > 1 || height >= QOI_PIXELS_MAX / width)
+            {
+                throw new ArgumentException("Invalid QOI file data");
+            }
+
+            var pixelsCount = width * height;
+            var pixels = new QoiPixel[pixelsCount];
+            var index = new QoiPixel[64];
+
+            var pixel = new QoiPixel(0, 0, 0, 255);
+
+            var run = 0;
+            var chunksLen = fileSize - QOI_PADDING_LENGTH;
+
+            for (var pixelIndex = 0; pixelIndex < pixelsCount; pixelIndex++)
+            {
+                if (run > 0)
+                {
+                    run--;
+                }
+                else if (stream.Position < chunksLen)
+                {
+                    var b1 = reader.ReadByte();
+
+                    if (b1 == QOI_OP_RGB)
+                    {
+                        pixel.R = reader.ReadByte();
+                        pixel.G = reader.ReadByte();
+                        pixel.B = reader.ReadByte();
+                    }
+                    else if (b1 == QOI_OP_RGBA)
+                    {
+                        pixel.R = reader.ReadByte();
+                        pixel.G = reader.ReadByte();
+                        pixel.B = reader.ReadByte();
+                        pixel.A = reader.ReadByte();
+                    }
+                    else if ((b1 & QOI_MASK_2) == QOI_OP_INDEX)
+                    {
+                        pixel = index[b1];
+                    }
+                    else if ((b1 & QOI_MASK_2) == QOI_OP_DIFF)
+                    {
+                        pixel.R += (byte)(((b1 >> 4) & 0x03) - 2);
+                        pixel.G += (byte)(((b1 >> 2) & 0x03) - 2);
+                        pixel.B += (byte)((b1 & 0x03) - 2);
+                    }
+                    else if ((b1 & QOI_MASK_2) == QOI_OP_LUMA)
+                    {
+                        var b2 = reader.ReadByte();
+                        var vg = (b1 & 0x3f) - 32;
+                        pixel.R += (byte)(vg - 8 + ((b2 >> 4) & 0x0f));
+                        pixel.G += (byte)vg;
+                        pixel.B += (byte)(vg - 8 + (b2 & 0x0f));
+                    }
+                    else if ((b1 & QOI_MASK_2) == QOI_OP_RUN)
+                    {
+                        run = b1 & 0x3f;
+                    }
+
+                    index[pixel.GetColorHash() % 64] = pixel;
+                }
+
+                pixels[pixelIndex] = pixel;
+            }
+
+            return ConvertToBitmap(width, height, channels, pixels);
+        }
+
+        private static Bitmap ConvertToBitmap(uint width, uint height, byte channels, QoiPixel[] pixels)
+        {
+            var pixelFormat = channels == 4 ? PixelFormat.Format32bppArgb : PixelFormat.Format24bppRgb;
+            var bitmap = new Bitmap((int)width, (int)height, pixelFormat);
+
+            var bitmapData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.WriteOnly, pixelFormat);
+
+            unsafe
+            {
+                for (var pixelIndex = 0; pixelIndex < pixels.Length; pixelIndex++)
+                {
+                    var pixel = pixels[pixelIndex];
+                    var bitmapPixel = (byte*)bitmapData.Scan0 + (pixelIndex * channels);
+
+                    bitmapPixel[0] = pixel.B;
+                    bitmapPixel[1] = pixel.G;
+                    bitmapPixel[2] = pixel.R;
+                    if (channels == 4)
+                    {
+                        bitmapPixel[3] = pixel.A;
+                    }
+                }
+            }
+
+            bitmap.UnlockBits(bitmapData);
+
+            return bitmap;
+        }
+
+        private static uint ReadUInt32BigEndian(BinaryReader reader)
+        {
+            var buffer = reader.ReadBytes(4);
+
+            return BinaryPrimitives.ReadUInt32BigEndian(buffer);
+        }
+    }
+}

src/modules/previewpane/common/Utilities/ReadonlyStream.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Runtime.InteropServices;
 using System.Runtime.InteropServices.ComTypes;
@@ -17,7 +18,7 @@ namespace Common.Utilities
     /// </remarks>
     public class ReadonlyStream : Stream
     {
-        private IStream _stream;
+        private IStream? _stream;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ReadonlyStream"/> class.
@@ -238,6 +239,7 @@ namespace Common.Utilities
             }
         }
 
+        [MemberNotNull(nameof(_stream))]
         private void CheckDisposed()
         {
             if (_stream == null)

src/modules/previewpane/common/examplehandler/CustomControlTest.cs

@@ -20,12 +20,12 @@ namespace Common
         /// <summary>
         /// WebView2 Control to display Svg.
         /// </summary>
-        private WebView2 _browser;
+        private WebView2? _browser;
 
         /// <summary>
         /// WebView2 Environment
         /// </summary>
-        private CoreWebView2Environment _webView2Environment;
+        private CoreWebView2Environment? _webView2Environment;
 
         /// <summary>
         /// Name of the virtual host
@@ -38,7 +38,7 @@ namespace Common
         /// <remarks>
         /// Source: https://stackoverflow.com/a/283917/14774889
         /// </remarks>
-        public static string AssemblyDirectory
+        public static string? AssemblyDirectory
         {
             get
             {
@@ -60,7 +60,7 @@ namespace Common
             _browser = new WebView2();
             _browser.Dock = DockStyle.Fill;
             _browser.Visible = true;
-            _browser.NavigationCompleted += (object sender, CoreWebView2NavigationCompletedEventArgs args) =>
+            _browser.NavigationCompleted += (object? sender, CoreWebView2NavigationCompletedEventArgs args) =>
             {
                 // Put here logic needed after WebView2 control is done navigating to url/page
             };
@@ -83,7 +83,7 @@ namespace Common
                     _browser.NavigateToString("Test");
 
                     // Or navigate to Uri
-                    _browser.Source = new Uri(filePath);
+                    _browser.Source = new Uri(filePath!);
                 }
                 catch (NullReferenceException)
                 {