AlbedoBaker.cs

using System.Drawing;
using System.Drawing.Imaging;
using System.Numerics;
using System.Runtime.InteropServices;

namespace RustMapViewer;

public static class AlbedoBaker
{
	private static readonly Vector4 StartColor = new(0.28627452f, 23f / 85f, 0.24705884f, 1f);
	private static readonly Vector4 WaterColor = new(0.16941601f, 0.31755757f, 0.36200002f, 1f);
	private static readonly Vector4 GravelColor = new(0.25f, 37f / 152f, 0.22039475f, 1f);
	private static readonly Vector4 DirtColor = new(0.6f, 0.47959462f, 0.33f, 1f);
	private static readonly Vector4 SandColor = new(0.7f, 0.65968585f, 0.5277487f, 1f);
	private static readonly Vector4 GrassColor = new(0.35486364f, 0.37f, 0.2035f, 1f);
	private static readonly Vector4 ForestColor = new(0.24843751f, 0.3f, 9f / 128f, 1f);
	private static readonly Vector4 RockColor = new(0.4f, 0.39379844f, 0.37519377f, 1f);
	private static readonly Vector4 SnowColor = new(0.86274517f, 0.9294118f, 0.94117653f, 1f);
	private static readonly Vector4 PebbleColor = new(7f / 51f, 0.2784314f, 0.2761563f, 1f);
	private static readonly Vector4 OffShoreColor = new(0.04090196f, 0.22060032f, 14f / 51f, 1f);
	private static readonly Vector3 SunDirection = Vector3.Normalize(new Vector3(0.95f, 2.87f, 2.37f));
	private static readonly Vector4 Half = new(0.5f, 0.5f, 0.5f, 0.5f);

	private const int ChDirt = 0;
	private const int ChSnow = 1;
	private const int ChSand = 2;
	private const int ChRock = 3;
	private const int ChGrass = 4;
	private const int ChForest = 5;
	private const int ChStones = 6;
	private const int ChGravel = 7;

	public static string BakeJpegDataUri(HeightMap height, SplatMap splat, float worldSize, int res, long jpegQuality = 85)
	{
		byte[] pixels = new byte[res * res * 3];
		float half = worldSize * 0.5f;
		float step = worldSize / (res - 1);

		Parallel.For(0, res, row =>
		{
			int z = res - 1 - row;
			float wz = -half + z * step;
			for (int x = 0; x < res; x++)
			{
				float wx = -half + x * step;
				float h = height.GetHeight(wx, wz);

				Vector4 c = StartColor;
				c = Vector4.Lerp(c, GravelColor, splat.GetSplat(wx, wz, ChGravel) * GravelColor.W);
				c = Vector4.Lerp(c, PebbleColor, splat.GetSplat(wx, wz, ChStones) * PebbleColor.W);
				c = Vector4.Lerp(c, RockColor, splat.GetSplat(wx, wz, ChRock) * RockColor.W);
				c = Vector4.Lerp(c, DirtColor, splat.GetSplat(wx, wz, ChDirt) * DirtColor.W);
				c = Vector4.Lerp(c, GrassColor, splat.GetSplat(wx, wz, ChGrass) * GrassColor.W);
				c = Vector4.Lerp(c, ForestColor, splat.GetSplat(wx, wz, ChForest) * ForestColor.W);
				c = Vector4.Lerp(c, SandColor, splat.GetSplat(wx, wz, ChSand) * SandColor.W);
				c = Vector4.Lerp(c, SnowColor, splat.GetSplat(wx, wz, ChSnow) * SnowColor.W);

				float depth = -h;
				if (depth > 0f)
				{
					c = Vector4.Lerp(c, WaterColor, Math.Clamp(0.5f + depth / 5f, 0f, 1f));
					c = Vector4.Lerp(c, OffShoreColor, Math.Clamp(depth / 50f, 0f, 1f));
				}
				else
				{
					float hl = height.GetHeight(wx - step, wz);
					float hr = height.GetHeight(wx + step, wz);
					float hd = height.GetHeight(wx, wz - step);
					float hu = height.GetHeight(wx, wz + step);
					Vector3 normal = Vector3.Normalize(new Vector3(hl - hr, 2f * step, hd - hu));
					float sun = MathF.Max(Vector3.Dot(normal, SunDirection), 0f);
					c += (sun - 0.5f) * 0.65f * c;
					c = (c - Half) * 0.94f + Half;
				}

				c *= 1.05f;
				int o = (row * res + x) * 3;
				pixels[o] = ToByte(c.Z);
				pixels[o + 1] = ToByte(c.Y);
				pixels[o + 2] = ToByte(c.X);
			}
		});

		using Bitmap bitmap = new(res, res, PixelFormat.Format24bppRgb);
		BitmapData data = bitmap.LockBits(new Rectangle(0, 0, res, res), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);
		try
		{
			for (int row = 0; row < res; row++)
			{
				Marshal.Copy(pixels, row * res * 3, data.Scan0 + row * data.Stride, res * 3);
			}
		}
		finally
		{
			bitmap.UnlockBits(data);
		}

		return JpegDataUri(bitmap, jpegQuality);
	}

	public static string JpegDataUri(Bitmap bitmap, long quality)
	{
		ImageCodecInfo codec = ImageCodecInfo.GetImageEncoders().First(e => e.FormatID == ImageFormat.Jpeg.Guid);
		using EncoderParameters encoderParams = new(1);
		encoderParams.Param[0] = new EncoderParameter(Encoder.Quality, quality);

		using MemoryStream ms = new();
		bitmap.Save(ms, codec, encoderParams);
		return "data:image/jpeg;base64," + Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
	}

	public static string PngDataUri(Bitmap bitmap)
	{
		using MemoryStream ms = new();
		bitmap.Save(ms, ImageFormat.Png);
		return "data:image/png;base64," + Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
	}

	private static byte ToByte(float v) => (byte)Math.Clamp(v * 255f, 0f, 255f);
}