Add pluggable image-comparison strategies with auto-selection, benchmarking, and test harness

.github/skills/code-review/SKILL.md

@@ -0,0 +1,17 @@
+# ImageComparator code review skill
+
+Use this skill to review pull requests in this repository with project-specific context.
+
+## Focus areas
+
+- Validate image-comparison correctness across strategies (`legacy`, `mad`, `dhash`, `auto`).
+- Check for numeric overflow risks in pixel and channel accumulation logic.
+- Verify `System.Drawing` pixel-format assumptions (especially 24bpp BGR byte order and stride handling).
+- Review CLI argument parsing edge cases (`--strategy`, `--benchmark`, `--benchmark-iterations`).
+- Ensure Windows-only behavior is explicit for `System.Drawing` paths and tests.
+- Confirm benchmark and test changes remain deterministic and minimal.
+
+## Review output expectations
+
+- Report only high-confidence correctness, security, or reliability issues.
+- Include exact file/line references and a concrete fix suggestion for each issue.

.github/workflows/ci.yml

@@ -19,13 +19,16 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: "8.0.x"
+          dotnet-version: "10.0.x"
 
       - name: Restore dependencies
         run: dotnet restore
 
       - name: Build
         run: dotnet build --no-restore --configuration Release
 
+      - name: Run tests
+        run: dotnet run --no-build --configuration Release --project ImageComparator.Tests/ImageComparator.Tests.csproj
+
       - name: Publish (self-contained)
         run: dotnet publish --no-build --configuration Release --output publish

ImageComparator.Tests/ImageComparator.Tests.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\ImageComparator\ImageComparator.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="TUnit" Version="1.64.13" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

ImageComparator.Tests/Program.cs

@@ -0,0 +1,99 @@
+namespace ImageComparator.Tests;
+
+using System.Drawing;
+using System.Runtime.Versioning;
+using ImageComparator;
+using TUnit.Core;
+
+public class BitmapCompareTests
+{
+    [Test]
+    [SupportedOSPlatform("windows")]
+    public async Task StrategiesRankIdenticalAboveDifferent()
+    {
+        if (!IsWindows())
+        {
+            Skip.Test("System.Drawing comparisons are Windows-only.");
+            return;
+        }
+
+        using var imageA = CreateSplitBitmap(Color.White, Color.Black);
+        using var imageB = CreateSplitBitmap(Color.White, Color.Black);
+        using var imageC = CreateSolidBitmap(Color.Blue);
+
+        var strategies = new[]
+        {
+            ComparisonStrategy.LegacyDominantChannel,
+            ComparisonStrategy.MeanAbsoluteDifference,
+            ComparisonStrategy.DifferenceHash,
+        };
+
+        foreach (var strategy in strategies)
+        {
+            var comparer = new BitmapCompare(strategy);
+            var sameSimilarity = comparer.GetSimilarity(imageA, imageB);
+            var differentSimilarity = comparer.GetSimilarity(imageA, imageC);
+
+            await Assert.That(sameSimilarity > differentSimilarity).IsTrue();
+        }
+    }
+
+    [Test]
+    [SupportedOSPlatform("windows")]
+    public async Task AutoStrategyPicksDifferenceHashForLargeImages()
+    {
+        if (!IsWindows())
+        {
+            Skip.Test("System.Drawing comparisons are Windows-only.");
+            return;
+        }
+        using var imageA = CreateSolidBitmap(Color.Green, width: 2400, height: 1600);
+        using var imageB = CreateSolidBitmap(Color.Green, width: 2400, height: 1600);
+        var comparer = new BitmapCompare(ComparisonStrategy.Auto);
+
+        _ = comparer.GetSimilarity(imageA, imageB);
+
+        await Assert.That(comparer.LastStrategyUsed).IsEqualTo(ComparisonStrategy.DifferenceHash);
+    }
+
+    [Test]
+    [SupportedOSPlatform("windows")]
+    public async Task BenchmarkReturnsConcreteStrategies()
+    {
+        if (!IsWindows())
+        {
+            Skip.Test("System.Drawing comparisons are Windows-only.");
+            return;
+        }
+
+        using var imageA = CreateSolidBitmap(Color.White);
+        using var imageB = CreateSolidBitmap(Color.Black);
+        var results = ComparisonBenchmark.Run(imageA, imageB, iterations: 3);
+
+        await Assert.That(results.Count).IsEqualTo(3);
+        await Assert.That(results.All(result => result.Strategy != ComparisonStrategy.Auto)).IsTrue();
+    }
+
+    [SupportedOSPlatform("windows")]
+    private static Bitmap CreateSolidBitmap(Color color, int width = 64, int height = 64)
+    {
+        var bitmap = new Bitmap(width, height);
+        using var graphics = Graphics.FromImage(bitmap);
+        graphics.Clear(color);
+        return bitmap;
+    }
+
+    [SupportedOSPlatform("windows")]
+    private static Bitmap CreateSplitBitmap(Color leftColor, Color rightColor, int width = 64, int height = 64)
+    {
+        var bitmap = new Bitmap(width, height);
+        using var graphics = Graphics.FromImage(bitmap);
+        graphics.Clear(rightColor);
+        using var brush = new SolidBrush(leftColor);
+        graphics.FillRectangle(brush, 0, 0, width / 2, height);
+        return bitmap;
+    }
+
+    [SupportedOSPlatformGuard("windows")]
+    private static bool IsWindows() => OperatingSystem.IsWindows();
+}

ImageComparator.sln

@@ -1,20 +1,46 @@
-
+
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 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ImageComparator", "ImageComparator\ImageComparator.csproj", "{04C06855-4D15-4E39-B460-257E4CC0B65A}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ImageComparator.Tests", "ImageComparator.Tests\ImageComparator.Tests.csproj", "{81EF9DFF-D736-4530-B67E-F942E7DBB5C9}"
+EndProject
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