Create a small demo application for StbImage.

ReFuel.StbImage.Viewer/Program.cs

@@ -0,0 +1,209 @@
+/*
+ * ReFuel.StbImage.Viewer - A simple image viewer demo for ReFuel.StbImage.
+ * ------------------------------------------------------------------------
+ *
+ * Pass an image file as path (or drag and drop over the executable or window) to view
+ * of the file formats stb_image supports. Otherwise the default embedded image will be
+ * shown.
+ *
+ * The demo uses OpenGL2.1 for brevity sake - I did not feel like writing a shader program
+ * for this demo. It is very easy to port this demo to modern OpenGL if desired. Just
+ * replace the FFP calls with the equivalent programmable pipeline calls (glVertexAttribPointer,
+ * glUseShader and its friends).
+ */
+
+using System.Reflection;
+using System.Runtime.InteropServices;
+using OpenTK.Graphics.OpenGL;
+using OpenTK.Mathematics;
+using OpenTK.Windowing.Common;
+using OpenTK.Windowing.Desktop;
+using ReFuel.Stb;
+
+NativeWindow window = new NativeWindow(new NativeWindowSettings()
+{
+    Profile = ContextProfile.Any,
+    APIVersion = new Version(2, 1),
+    Title = "ReFuel StbImage Viewer",
+    AutoLoadBindings = true,
+    Flags = ContextFlags.Default,
+});
+
+bool quit = false;
+int texture = 0;
+int imageWidth = 0, imageHeight = 0;
+
+// This flag is important for OpenGL users, as texture coordinate systems
+// are the opposite of what most image formats use. Y is up not down.
+// Does not matter for DX, for example.
+StbImage.FlipVerticallyOnLoad = true;
+
+Vertex[] vertices = new Vertex[]
+{
+    new Vertex(-1, -1, 0, 0),
+    new Vertex(1, -1, 1, 0),
+    new Vertex(1, 1, 1, 1),
+    new Vertex(-1, -1, 0, 0),
+    new Vertex(1, 1, 1, 1),
+    new Vertex(-1, 1, 0, 1),
+};
+
+LoadImage(args.Length > 0 ? args[0] : null);
+
+GL.ClearColor(Color4.Black);
+GL.Enable(EnableCap.Texture2D);
+GL.Enable(EnableCap.Blend);
+GL.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha); // conventional blending function.
+GL.EnableClientState(ArrayCap.VertexArray);
+GL.EnableClientState(ArrayCap.TextureCoordArray);
+GL.EnableClientState(ArrayCap.ColorArray);
+
+window.Closing += (_) => quit = true;
+window.FramebufferResize += (_) => {
+    ResizeImage();
+    Paint();
+};
+window.FileDrop += (args) => 
+    LoadImage(
+        args.FileNames
+            .Select(x => new FileInfo(x))
+            .FirstOrDefault(x => x.Exists)?.FullName);
+
+window.WindowState = WindowState.Normal;
+while (!quit)
+{
+    NativeWindow.ProcessWindowEvents(true);
+    Paint();
+};
+
+void Paint()
+{
+    GL.Clear(ClearBufferMask.ColorBufferBit);
+    GL.Viewport(0, 0, window.FramebufferSize.X, window.FramebufferSize.Y);
+    GL.BindTexture(TextureTarget.Texture2D, texture);
+
+    unsafe
+    {
+        fixed (Vertex* pvert = vertices)
+        {
+            // We have to do it this way because the garbage collector may
+            // move the vertex data at any time. The OpenGL client will
+            // handle streaming the data at the glDrawArrays call, unlike
+            // the modern method.
+            GL.VertexPointer(2, VertexPointerType.Float, 32, (nint)(&pvert->X));
+            GL.TexCoordPointer(2, TexCoordPointerType.Float, 32, (nint)(&pvert->U));
+            GL.ColorPointer(4, ColorPointerType.Float, 32, (nint)(&pvert->Color));
+            GL.DrawArrays(PrimitiveType.Triangles, 0, vertices.Length);
+        }
+    }
+
+    window.Context.SwapBuffers();
+}
+
+void ResizeImage()
+{
+    // Regenerates the vertex positions to maintain the aspect ratio and fill the window.
+    float windowAspect = (float)window.FramebufferSize.X / window.FramebufferSize.Y;
+    float imageAspect = (float)imageWidth / imageHeight;
+    float ratio = imageAspect / windowAspect;
+
+    float widthNDC, heightNDC;
+    if (ratio > 1)
+    {
+        widthNDC = 2.0f;
+        heightNDC = 2.0f / ratio;
+    }
+    else
+    {
+        heightNDC = 2.0f;
+        widthNDC = 2.0f * ratio;
+    }
+
+    vertices[0].X = -widthNDC / 2; vertices[0].Y = -heightNDC / 2;
+    vertices[1].X = widthNDC / 2; vertices[1].Y = -heightNDC / 2;
+    vertices[2].X = widthNDC / 2; vertices[2].Y = heightNDC / 2;
+    vertices[3].X = -widthNDC / 2; vertices[3].Y = -heightNDC / 2;
+    vertices[4].X = widthNDC / 2; vertices[4].Y = heightNDC / 2;
+    vertices[5].X = -widthNDC / 2; vertices[5].Y = heightNDC / 2;
+}
+
+void LoadImage(string? path)
+{
+    // Load the given image, or the default if the path is null, or any other error happens.
+    StbImage? image = null;
+    if (path != null && File.Exists(path))
+    {
+        try
+        {
+            using Stream str = File.OpenRead(path);
+            StbImage.TryLoad(out image, str);
+        }
+        catch
+        {
+            // Ignore
+        }
+    }
+
+    if (image == null)
+    {
+        using Stream str = Assembly.GetExecutingAssembly().GetManifestResourceStream("default.png")!;
+        image = StbImage.Load(str);
+    }
+
+    // Boilerplate code for creating a new OpenGL texture.
+
+    GL.DeleteTexture(texture);
+    texture = GL.GenTexture();
+    GL.BindTexture(TextureTarget.Texture2D, texture);
+    GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, image.Width, image.Height, 0, image.Format switch
+    {
+        StbiImageFormat.Grey => PixelFormat.Red,
+        StbiImageFormat.GreyAlpha => PixelFormat.Rg,
+        StbiImageFormat.Rgb => PixelFormat.Rgb,
+        StbiImageFormat.Rgba => PixelFormat.Rgba,
+        _ => throw new Exception()
+    }, image.IsFloat ? PixelType.Float : PixelType.UnsignedByte, image.ImagePointer);
+    
+    // Generate mipmaps for better minification.
+    GL.GenerateMipmap(GenerateMipmapTarget.Texture2D);
+    // Enable them.
+    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)TextureMinFilter.LinearMipmapLinear);
+    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)TextureMagFilter.Linear);
+
+    // Set texture wrap mode to clamp to border to prevent bleeding on the image edges.
+    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)TextureWrapMode.ClampToBorder);
+    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)TextureWrapMode.ClampToBorder);
+
+    // For R or RA format images, we need to set the swizzle mask.
+    switch (image.Format)
+    {
+        case StbiImageFormat.Grey:
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleR, (int)TextureSwizzle.Red);
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleG, (int)TextureSwizzle.Red);
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleB, (int)TextureSwizzle.Red);
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleA, (int)TextureSwizzle.One);
+            break;
+        case StbiImageFormat.GreyAlpha:
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleR, (int)TextureSwizzle.Red);
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleG, (int)TextureSwizzle.Red);
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleA, (int)TextureSwizzle.Green);
+            // Yes the last channel is green, we uploaded the texture with the Rg color format.
+            GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureSwizzleB, (int)TextureSwizzle.Red);
+            break;
+    }
+
+    imageWidth = image.Width;
+    imageHeight = image.Height;
+    ResizeImage();
+
+    image.Dispose();
+}
+
+// Vertex struct for convenience. Padded to 32 bytes for memory alignment.
+[StructLayout(LayoutKind.Sequential, Size = 32)]
+struct Vertex(float x, float y, float u, float v)
+{
+    public float X = x, Y = y, U = u, V = v;
+    public Color4 Color = Color4.White;
+}
+

ReFuel.StbImage.Viewer/ReFuel.StbImage.Viewer.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- <ProjectReference Include="..\ReFuel.StbImage\ReFuel.StbImage.csproj" /> -->
+    <PackageReference Include="ReFuel.StbImage" Version="2.1.0"/>
+    <PackageReference Include="OpenTK" Version="4.9.4" /> 
+    <EmbeddedResource Include="../rf_stbimage.png" LogicalName="default.png"/>
+  </ItemGroup>
+
+</Project>

ReFuel.StbImage.sln

@@ -3,20 +3,46 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.0.31903.59
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ReFuel.StbImage", "ReFuel.StbImage.csproj", "{413ACBF4-3851-416F-B2A2-F7157EC306B2}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ReFuel.StbImage", "ReFuel.StbImage\ReFuel.StbImage.csproj", "{EB001CC8-6821-4579-BD5D-27C56A3C121E}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ReFuel.StbImage.Viewer", "ReFuel.StbImage.Viewer\ReFuel.StbImage.Viewer.csproj", "{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
+		Debug|x64 = Debug|x64
+		Debug|x86 = Debug|x86
 		Release|Any CPU = Release|Any CPU
+		Release|x64 = Release|x64
+		Release|x86 = Release|x86
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Debug|x64.Build.0 = Debug|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Debug|x86.Build.0 = Debug|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Release|x64.ActiveCfg = Release|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Release|x64.Build.0 = Release|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Release|x86.ActiveCfg = Release|Any CPU
+		{EB001CC8-6821-4579-BD5D-27C56A3C121E}.Release|x86.Build.0 = Release|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Debug|x64.Build.0 = Debug|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Debug|x86.Build.0 = Debug|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Release|Any CPU.Build.0 = Release|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Release|x64.ActiveCfg = Release|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Release|x64.Build.0 = Release|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Release|x86.ActiveCfg = Release|Any CPU
+		{4CFB8D5B-8CE9-46EE-A34B-0D61693BDE50}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
-	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{413ACBF4-3851-416F-B2A2-F7157EC306B2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{413ACBF4-3851-416F-B2A2-F7157EC306B2}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{413ACBF4-3851-416F-B2A2-F7157EC306B2}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{413ACBF4-3851-416F-B2A2-F7157EC306B2}.Release|Any CPU.Build.0 = Release|Any CPU
-	EndGlobalSection
 EndGlobal

ReFuel.StbImage/ReFuel.StbImage.csproj

@@ -14,7 +14,7 @@
     <!-- Nuget Properties. -->
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <PackageId>ReFuel.StbImage</PackageId>
-    <Version>2.0.2-rc.1</Version>
+    <Version>2.1.0</Version>
     <Authors>STBI Authors, H. Utku Maden</Authors>
     <Description>
       A C# wrapper for the ubiquitous stb_image.h and stb_image_write.h library.
@@ -26,10 +26,10 @@
     <RepositoryUrl>https://git.mixedup.dev/ReFuel/ReFuel.StbImage</RepositoryUrl>
     <RepositoryType>git</RepositoryType>
     <PackageTags>stb; stb_image; stbi; image; load; save; read; write</PackageTags>
-    <PackageReleaseNotes># 2.0.2
+    <PackageReleaseNotes># 2.1.0 (ABI BRAKING)
 * Fixed calling convention of unmanaged function pointers. (Thanks NogginBops!)
-* Allocating a GC handle to StbiStreamWrapper class and passing it as userdata into stbi in order to prevent
-  the object from being prematurely collected by the garbage collector when optimizations are enabled in Release mode.
+* Modified StbiStreamWrapper in order to fixed backing delegates of function pointers from being prematurely collected 
+  by release mode JIT and the GC. StbiStreamWrapper.Callbacks is now a readonly field. (ABI BREAKING)
 
 # 2.0.1
 * Enabled optimizations across the board for native and managed assemblies.
@@ -56,7 +56,7 @@
     <Content Include="runtimes/linux-arm64/native/*.so">
       <PackagePath>runtimes/linux-arm64/native/</PackagePath>
       <Pack>true</Pack>
-      <CopyToOutputDirectory>PreserveNewest/</CopyToOutputDirectory>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
     <Content Include="runtimes/linux-x64/native/*.so">
       <PackagePath>runtimes/linux-x64/native/</PackagePath>

ReFuel.StbImage/StbImage.cs

@@ -209,19 +209,19 @@ namespace ReFuel.Stb
         {
             int x, y, iFormat;
             StbiStreamWrapper wrapper = new StbiStreamWrapper(stream, true);
-            GCHandle gch = GCHandle.Alloc(wrapper, GCHandleType.Normal);
-            wrapper.CreateCallbacks(out stbi_io_callbacks cb);
             stream.Position = 0;
             IntPtr imagePtr;
-            if (asFloat)
+            fixed (stbi_io_callbacks* cb = &wrapper.Callbacks)
             {
-                imagePtr = (IntPtr)Stbi.loadf_from_callbacks(&cb, (void*)(IntPtr)gch, &x, &y, &iFormat, (int)format);
+                if (asFloat)
+                {
+                    imagePtr = (IntPtr)Stbi.loadf_from_callbacks(cb, null, &x, &y, &iFormat, (int)format);
+                }
+                else
+                {
+                    imagePtr = (IntPtr)Stbi.load_from_callbacks(cb, null, &x, &y, &iFormat, (int)format);
+                }
             }
-            else
-            {
-                imagePtr = (IntPtr)Stbi.load_from_callbacks(&cb, (void*)(IntPtr)gch, &x, &y, &iFormat, (int)format);
-            }
-            gch.Free();
 
             if (imagePtr != IntPtr.Zero)
             {
@@ -319,10 +319,12 @@ namespace ReFuel.Stb
         {
             int x, y, iFormat;
             StbiStreamWrapper wrapper = new StbiStreamWrapper(stream, true);
-            wrapper.CreateCallbacks(out stbi_io_callbacks cb);
-
+            int result;
             stream.Position = 0;
-            int result = Stbi.info_from_callbacks(&cb, null, &x, &y, &iFormat);
+            fixed (stbi_io_callbacks* cb = &wrapper.Callbacks)
+            {
+                result = Stbi.info_from_callbacks(cb, null, &x, &y, &iFormat);
+            }
 
             width = x;
             height = y;

ReFuel.StbImage/StbiStreamWrapper.cs

@@ -32,11 +32,12 @@ namespace ReFuel.Stb
     public unsafe delegate int StbiEofProc(void *userdata);
 
     /// <summary>
-    /// An easy to use stream wrapper for use with STBI image load functions.
+    /// An easy-to-use stream wrapper for use with STBI image load functions.
     /// </summary>
     public unsafe class StbiStreamWrapper : IDisposable
     {
-        private readonly stbi_io_callbacks _callbacks;
+        public readonly stbi_io_callbacks Callbacks;
+
         private readonly Stream _stream;
         private readonly bool _keepOpen;
         private bool _isDisposed;
@@ -45,8 +46,6 @@ namespace ReFuel.Stb
         private StbiSkipProc _skipCb;
         private StbiEofProc _eofCb;
 
-        public ref readonly stbi_io_callbacks Callbacks => ref _callbacks;
-
         public StbiStreamWrapper(Stream stream, bool keepOpen = false)
         {
             if (stream == null) throw new ArgumentNullException(nameof(stream));
@@ -58,18 +57,10 @@ namespace ReFuel.Stb
             _skipCb = SkipCb;
             _eofCb = EofCb;
 
-            _callbacks = default;
-            _callbacks.read = Marshal.GetFunctionPointerForDelegate<StbiReadProc>(_readCb);
-            _callbacks.skip = Marshal.GetFunctionPointerForDelegate<StbiSkipProc>(_skipCb);
-            _callbacks.eof = Marshal.GetFunctionPointerForDelegate<StbiEofProc>(_eofCb);
-        }
-
-        public void CreateCallbacks(out stbi_io_callbacks cb)
-        {
-            cb = default;
-            cb.read = Marshal.GetFunctionPointerForDelegate<StbiReadProc>(_readCb);
-            cb.skip = Marshal.GetFunctionPointerForDelegate<StbiSkipProc>(_skipCb);
-            cb.eof = Marshal.GetFunctionPointerForDelegate<StbiEofProc>(_eofCb);
+            Callbacks = default;
+            Callbacks.read = Marshal.GetFunctionPointerForDelegate<StbiReadProc>(_readCb);
+            Callbacks.skip = Marshal.GetFunctionPointerForDelegate<StbiSkipProc>(_skipCb);
+            Callbacks.eof = Marshal.GetFunctionPointerForDelegate<StbiEofProc>(_eofCb);
         }
 
         private int ReadCb(void *userdata, byte* buffer, int count)