C#で作るイラストから線画抽出するコンソールアプリ

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net9.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="OpenCvSharp4" Version="4.11.0.20250507" />
    <PackageReference Include="OpenCvSharp4.runtime.win" Version="4.11.0.20250507" />
  </ItemGroup>

</Project>

using System.ComponentModel;
using System.Globalization;

public class Opt
{
    public string Input { get; set; } = "";
    public string? Output { get; set; } = null;
    public double Gamma { get; set; } = 0.75;
    public static Opt ParseArgs(string[] a)
    {
        var o = new Opt();
        string? key = null;
        foreach (var token in a)
        {
            if (token.StartsWith("-"))
            {
                key = token;
            }
            else
            {
                switch (key)
                {
                    case "-i": case "--in": o.Input = token; break;
                    case "-o": case "--out": o.Output = token; break;
                    default:
                        // 位置引数互換
                        if (string.IsNullOrEmpty(o.Input)) o.Input = token;
                        else if (o.Output is null) o.Output = token;
                        break;
                }
                key = null;
            }
        }
        return o;
    }
    public static void PrintHelp()
    {
        Console.Error.WriteLine(
@"Usage:
  toline -i <input> [options]
  toline <input> [output.png]

Options:
  -i, --in <path>          入力ファイル
  -o, --out <path>         出力ファイル（省略時: <input>_line.png）
");
    }

}

// C#で作る適応値型2値化で線画を抽出するコンソールアプリ

// ビルドコマンド
// dotnet publish -r win-x64 -c Release /p:PublishSingleFile=true /p:IncludeAllContentForSelfExtract=true /p:SelfContained=true --output "exeの出力先のディレクトリ"
using OpenCvSharp;

class Program
{
    static void Main(string[] args)
    {
        if (args.Length == 0 || args.Contains("-h") || args.Contains("--help"))
        {
            Opt.PrintHelp();
            Environment.Exit(1);
        }

        var opt = Opt.ParseArgs(args);
        if (string.IsNullOrWhiteSpace(opt.Input))
        {
            Opt.PrintHelp();
            Environment.Exit(1);
        }

        string output = opt.Output ?? Path.Combine(
            Path.GetDirectoryName(opt.Input) ?? "",
            Path.GetFileNameWithoutExtension(opt.Input) + "_line.png");

        imageFilter(opt.Input, output, opt.Gamma);

        Console.WriteLine(output);
    }

    static void imageFilter(string inputPath, string outputPath, double gamma)
    {
        using var src = Cv2.ImRead(inputPath);

        if (src is null) return;
        if (src.Channels() == 3)
            Cv2.CvtColor(src, src, ColorConversionCodes.BGR2GRAY);
        if (src.Channels() == 4)
            Cv2.CvtColor(src, src, ColorConversionCodes.BGRA2GRAY);
        if (src.Channels() != 1)
            return;
        using var element = Cv2.GetStructuringElement(MorphShapes.Ellipse, new OpenCvSharp.Size(3, 3));
        using var work = new Mat();
        using var dst = new Mat();
        Cv2.AdaptiveThreshold(src, work, 255.0,
            AdaptiveThresholdTypes.GaussianC,
            ThresholdTypes.BinaryInv,
            51, 20);
        Cv2.Dilate(work, work, element);
        Cv2.Erode(work, work, element);
        Cv2.BitwiseNot(work, dst);         

        Cv2.ImWrite(outputPath, dst);
    }
}