Palettizer2/src/Program.cs

using System.CommandLine;
using System.CommandLine.Invocation;
using System.IO;
using StbImageSharp;

namespace Palettizer2
{
    class Program
    {
        static int Main(string[] args)
        {
            var palettize = new Command("palettize")
            {
                new Argument<DirectoryInfo>(
                    "directory",
                    "Path to a directory containing PNG files."
                ),
				new Argument<string>(
					"paletteName",
					"The name of the palette sprite to output."
				)
            };

            var root = new RootCommand{
	            palettize
            };

            palettize.Handler = CommandHandler.Create<DirectoryInfo, string>(HandlePalettize);
            return root.Invoke(args);
        }

        static void HandlePalettize(DirectoryInfo directory, string paletteName)
        {
	        var outputDir = Directory.CreateDirectory("output");
	        var palette = new Palette();
	        var writer = new StbImageWriteSharp.ImageWriter();

	        // add all sprite colors to palette
	        foreach (var imageFile in directory.EnumerateFiles("*.png"))
	        {
		        System.Console.WriteLine(imageFile.FullName);

		        var spriteDir = Path.GetDirectoryName(imageFile.FullName);

		        ImageResult image;
		        byte[] grayscaleImageBytes;
		        using (var stream = File.OpenRead(imageFile.FullName))
		        {
			        image = ImageResult.FromStream(stream, ColorComponents.RedGreenBlueAlpha);
			        grayscaleImageBytes = AddSpriteToPalette(palette, image);
		        }

		        var spriteWriteDir = Path.Combine(
			        outputDir.FullName,
			        Path.GetRelativePath(directory.FullName, spriteDir));

		        Directory.CreateDirectory(spriteWriteDir);
		        var spriteWritePath = Path.Combine(spriteWriteDir, imageFile.Name);

		        using (var stream = File.OpenWrite(spriteWritePath))
		        {
			        writer.WritePng(
				        grayscaleImageBytes,
				        image.Width,
				        image.Height,
				        StbImageWriteSharp.ColorComponents.RedGreenBlueAlpha,
				        stream);
		        }
	        }

	        // write palette sprite to PNG
	        var paletteOutputPath = Path.Combine(outputDir.FullName, paletteName + ".png");
	        using (var stream = File.OpenWrite(paletteOutputPath))
	        {
		        writer.WritePng(
			        palette.CreateIndexedPaletteBitmap(),
			        palette.Width,
			        palette.Height,
			        StbImageWriteSharp.ColorComponents.RedGreenBlueAlpha,
			        stream);
	        }
        }

        static byte[] AddSpriteToPalette(Palette palette, ImageResult image)
		{
			var grayscaleImage = new byte[image.Width * image.Height * 4];

			for (var i = 0; i < image.Width * image.Height * 4; i += 4)
			{
				var color = new Color
				{
					R = image.Data[i],
					G = image.Data[i + 1],
					B = image.Data[i + 2],
					A = image.Data[i + 3]
				};

				if (color.A == 0)
				{
					continue;
				}

				if (palette.ColorToGrayscaleMap.ContainsKey(color))
				{
					var grayscaleColor = palette.ColorToGrayscaleMap[color];

					grayscaleImage[i] = grayscaleColor;
					grayscaleImage[i + 1] = grayscaleColor;
					grayscaleImage[i + 2] = grayscaleColor;
					grayscaleImage[i + 3] = color.A;
				}
				else
				{
					if (palette.GrayscaleCount == 256)
					{
						System.Console.WriteLine("Too many colors! Bailing!");
						return grayscaleImage;
					}
					else
					{
                        palette.AddColor(color);

						var grayscaleColor = palette.ColorToGrayscaleMap[color];

						grayscaleImage[i] = grayscaleColor;
						grayscaleImage[i + 1] = grayscaleColor;
						grayscaleImage[i + 2] = grayscaleColor;
						grayscaleImage[i + 3] = color.A;
					}
				}
			}

			return grayscaleImage;
		}
    }
}