acdream/tools/TextureDump/Program.cs

// TextureDump — probe rain-streak textures (0x050016A4..0x050016A8) for
// the volumetric rain density-trick decision.
using System;
using System.IO;
using System.IO.Compression;
using AcDream.Core.Textures;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using DatReaderWriter.Options;
using SysEnv = System.Environment;

string datDir = SysEnv.GetEnvironmentVariable("ACDREAM_DAT_DIR")
    ?? Path.Combine(SysEnv.GetFolderPath(SysEnv.SpecialFolder.UserProfile),
                    "Documents", "Asheron's Call");

Console.WriteLine($"datDir = {datDir}");
using var dats = new DatCollection(datDir, DatAccessType.Read);

string outDir = Path.Combine(AppContext.BaseDirectory, "out");
Directory.CreateDirectory(outDir);
Console.WriteLine($"outDir = {outDir}");

// Original ask: 0x050016A4..0x050016A8. A4/A5/A7/A8 don't exist as files; widen
// to 0x050016A0..0x050016AF to catch any related precip textures.
var idList = new System.Collections.Generic.List<uint>();
for (uint i = 0x050016A0; i <= 0x050016AF; i++) idList.Add(i);
uint[] ids = idList.ToArray();

(uint id, double densityFraction)? best = null;

foreach (var id in ids)
{
    Console.WriteLine();
    Console.WriteLine($"=== 0x{id:X8} ===");

    RenderSurface? rs = null;
    // SurfaceTexture wrapper (0x05xxxxxx) → first inner RenderSurface (0x06xxxxxx).
    if (dats.TryGet<SurfaceTexture>(id, out var st) && st is not null && st.Textures.Count > 0)
    {
        uint rsid = (uint)st.Textures[0];
        Console.WriteLine($"  SurfaceTexture wrapper, {st.Textures.Count} mip(s), first = 0x{rsid:X8}");
        if (dats.TryGet<RenderSurface>(rsid, out var inner) && inner is not null)
            rs = inner;
    }
    else if (dats.TryGet<RenderSurface>(id, out var direct) && direct is not null)
    {
        rs = direct;
    }
    if (rs is null)
    {
        Console.WriteLine("  (not a SurfaceTexture or RenderSurface, or not found)");
        continue;
    }

    Console.WriteLine($"  Dimensions: {rs.Width} x {rs.Height}");
    Console.WriteLine($"  PixelFormat: {rs.Format} (0x{(uint)rs.Format:X8})");
    Console.WriteLine($"  SourceData bytes: {rs.SourceData?.Length ?? 0}");
    Console.WriteLine($"  DefaultPaletteId: 0x{rs.DefaultPaletteId:X8}");

    Palette? palette = null;
    if (rs.DefaultPaletteId != 0)
    {
        if (dats.TryGet<Palette>(rs.DefaultPaletteId, out var pal) && pal is not null)
        {
            palette = pal;
            Console.WriteLine($"  Palette colors: {pal.Colors.Count}");
        }
    }

    var dec = SurfaceDecoder.DecodeRenderSurface(rs, palette);
    if (dec.Rgba8 is null || dec.Rgba8.Length == 0)
    {
        Console.WriteLine("  DECODE FAILED.");
        continue;
    }

    // Stats: alpha histogram (8 buckets), brightness mean/stddev, bright count.
    int n = dec.Width * dec.Height;
    int[] alphaBuckets = new int[8]; // 0..31, 32..63, ..., 224..255
    long sumB = 0;
    long sumBSq = 0;
    int brightAlpha = 0; // alpha > 128
    int brightLum = 0;   // brightness > 200
    int litLum = 0;      // brightness > 16 (any visible pixel)
    int midLum = 0;      // brightness > 64
    int nonZeroAlpha = 0;
    int maxLum = 0;
    for (int i = 0; i < n; i++)
    {
        byte r = dec.Rgba8[i * 4 + 0];
        byte g = dec.Rgba8[i * 4 + 1];
        byte b = dec.Rgba8[i * 4 + 2];
        byte a = dec.Rgba8[i * 4 + 3];
        int lum = (r + g + b) / 3;
        sumB += lum;
        sumBSq += (long)lum * lum;
        alphaBuckets[Math.Min(7, a / 32)]++;
        if (a > 128) brightAlpha++;
        if (lum > 200) brightLum++;
        if (lum > 64) midLum++;
        if (lum > 16) litLum++;
        if (a > 0) nonZeroAlpha++;
        if (lum > maxLum) maxLum = lum;
    }
    double mean = (double)sumB / n;
    double variance = ((double)sumBSq / n) - mean * mean;
    double stddev = Math.Sqrt(Math.Max(0, variance));

    Console.WriteLine($"  Pixels: {n}");
    Console.Write("  Alpha histogram (8 buckets, 0->255):");
    for (int b = 0; b < 8; b++) Console.Write($" {alphaBuckets[b]}");
    Console.WriteLine();
    Console.WriteLine($"  Brightness mean = {mean:F2}, stddev = {stddev:F2}, max = {maxLum}");
    Console.WriteLine($"  Lit pixels: lum>16 = {litLum} ({100.0 * litLum / n:F3}%)  lum>64 = {midLum} ({100.0 * midLum / n:F3}%)  lum>200 = {brightLum} ({100.0 * brightLum / n:F3}%)");
    Console.WriteLine($"  alpha>128 = {brightAlpha} ({100.0 * brightAlpha / n:F2}%)  nonZeroAlpha = {nonZeroAlpha} ({100.0 * nonZeroAlpha / n:F2}%)");

    // "Density" for fake-volumetric look: % of pixels that contribute a visible
    // streak. Use max(alpha>128, lum>200, nonZeroAlpha) as the proxy — different
    // textures encode the streak via either alpha-clip or pure luminance.
    double densityFrac = Math.Max(brightAlpha, Math.Max(brightLum, nonZeroAlpha)) / (double)n;
    if (best is null || densityFrac > best.Value.densityFraction)
        best = (id, densityFrac);

    string pngPath = Path.Combine(outDir, $"tex_{id:X8}.png");
    WritePng(pngPath, dec.Rgba8, dec.Width, dec.Height);
    Console.WriteLine($"  PNG: {pngPath}");
}

Console.WriteLine();
if (best is not null)
    Console.WriteLine($"DENSEST: 0x{best.Value.id:X8} (density frac {best.Value.densityFraction:F4})");
return 0;

// -------- Minimal PNG encoder (RGBA8, no filter, single IDAT, zlib via DeflateStream) --------
static void WritePng(string path, byte[] rgba, int width, int height)
{
    using var fs = File.Create(path);
    // Signature
    fs.Write(new byte[] { 0x89, (byte)'P', (byte)'N', (byte)'G', 0x0D, 0x0A, 0x1A, 0x0A });

    // IHDR
    var ihdr = new byte[13];
    WriteBE(ihdr, 0, (uint)width);
    WriteBE(ihdr, 4, (uint)height);
    ihdr[8] = 8;        // bit depth
    ihdr[9] = 6;        // color type RGBA
    ihdr[10] = 0;       // compression
    ihdr[11] = 0;       // filter
    ihdr[12] = 0;       // interlace
    WriteChunk(fs, "IHDR", ihdr);

    // IDAT: rows prefixed with filter byte 0, zlib-wrapped deflate.
    using var raw = new MemoryStream();
    for (int y = 0; y < height; y++)
    {
        raw.WriteByte(0);
        raw.Write(rgba, y * width * 4, width * 4);
    }
    byte[] uncompressed = raw.ToArray();

    using var compressed = new MemoryStream();
    // zlib header: 0x78 0x9C (deflate, default compression)
    compressed.WriteByte(0x78);
    compressed.WriteByte(0x9C);
    using (var deflate = new DeflateStream(compressed, CompressionLevel.Fastest, leaveOpen: true))
        deflate.Write(uncompressed, 0, uncompressed.Length);
    // Adler-32 of uncompressed data, big-endian.
    uint adler = Adler32(uncompressed);
    compressed.WriteByte((byte)(adler >> 24));
    compressed.WriteByte((byte)(adler >> 16));
    compressed.WriteByte((byte)(adler >> 8));
    compressed.WriteByte((byte)adler);

    WriteChunk(fs, "IDAT", compressed.ToArray());
    WriteChunk(fs, "IEND", Array.Empty<byte>());
}

static void WriteBE(byte[] buf, int offset, uint v)
{
    buf[offset + 0] = (byte)(v >> 24);
    buf[offset + 1] = (byte)(v >> 16);
    buf[offset + 2] = (byte)(v >> 8);
    buf[offset + 3] = (byte)v;
}

static void WriteChunk(Stream s, string type, byte[] data)
{
    var len = new byte[4];
    WriteBE(len, 0, (uint)data.Length);
    s.Write(len);
    var typeBytes = System.Text.Encoding.ASCII.GetBytes(type);
    s.Write(typeBytes);
    s.Write(data);
    var crcInput = new byte[typeBytes.Length + data.Length];
    Buffer.BlockCopy(typeBytes, 0, crcInput, 0, typeBytes.Length);
    Buffer.BlockCopy(data, 0, crcInput, typeBytes.Length, data.Length);
    uint crc = Crc32(crcInput);
    s.WriteByte((byte)(crc >> 24));
    s.WriteByte((byte)(crc >> 16));
    s.WriteByte((byte)(crc >> 8));
    s.WriteByte((byte)crc);
}

static uint Crc32(byte[] data)
{
    uint c = 0xFFFFFFFFu;
    foreach (var b in data)
    {
        uint v = (c ^ b) & 0xFF;
        for (int k = 0; k < 8; k++)
            v = ((v & 1) != 0) ? (0xEDB88320u ^ (v >> 1)) : (v >> 1);
        c = v ^ (c >> 8);
    }
    return c ^ 0xFFFFFFFFu;
}

static uint Adler32(byte[] data)
{
    const uint MOD = 65521;
    uint a = 1, b = 0;
    foreach (var x in data)
    {
        a = (a + x) % MOD;
        b = (b + a) % MOD;
    }
    return (b << 16) | a;
}