remapsmoke.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

namespace remapsmoke
{
	class Program
	{
		static void Main(string[] args)
		{
			foreach (var fn in Directory.GetFiles(@"d:\\crap\temphax\", "*.png"))
			{
				using (var img = (Bitmap)Bitmap.FromFile(fn))
				{
					UsedColors(img);
					img.Save(@"d:\\crap\output\" + Path.GetFileName(fn));
				}
			}
		}

		static byte RemapColor(byte c)
		{
			if (c < 0x90 || c >= 0x9c) return c;
			return (byte)(((c - 0x90) * 4) / 3 + 0x50);
		}

		static void UsedColors(Bitmap b)
		{
			var data = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);

			unsafe
			{
				var p = (byte*)data.Scan0;
				for (var i = 0; i < b.Width; i++)
					for (var j = 0; j < b.Height; j++)
						p[j * data.Stride + i] = RemapColor(p[j * data.Stride + i]);
			}

			b.UnlockBits(data);
		}
	}
}