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
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+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
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+		Release|x86 = Release|x86
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+		{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
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