poe2-bot/src/Poe2Trade.Screen/DetectGridHandler.cs

namespace Poe2Trade.Screen;

using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using Serilog;
using Region = Poe2Trade.Core.Region;

class DetectGridHandler
{
    public DetectGridResult Detect(Region region, int minCellSize = 20, int maxCellSize = 70,
        string? file = null, bool debug = false)
    {
        Bitmap bitmap = ScreenCapture.CaptureOrLoad(file, region);
        int w = bitmap.Width;
        int h = bitmap.Height;

        var bmpData = bitmap.LockBits(
            new Rectangle(0, 0, w, h),
            ImageLockMode.ReadOnly,
            PixelFormat.Format32bppArgb
        );
        byte[] pixels = new byte[bmpData.Stride * h];
        Marshal.Copy(bmpData.Scan0, pixels, 0, pixels.Length);
        bitmap.UnlockBits(bmpData);
        int stride = bmpData.Stride;

        byte[] gray = new byte[w * h];
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++)
            {
                int i = y * stride + x * 4;
                gray[y * w + x] = (byte)((pixels[i] + pixels[i + 1] + pixels[i + 2]) / 3);
            }

        bitmap.Dispose();

        int bandH = 200;
        int bandStep = 40;
        const int veryDarkPixelThresh = 12;
        const double gridSegThresh = 0.25;

        var candidates = new List<(int bandY, int cellW, double hAc, int hLeft, int hRight)>();

        for (int by = 0; by + bandH <= h; by += bandStep)
        {
            double[] darkDensity = new double[w];
            for (int x = 0; x < w; x++)
            {
                int count = 0;
                for (int y = by; y < by + bandH; y++)
                {
                    if (gray[y * w + x] < veryDarkPixelThresh) count++;
                }
                darkDensity[x] = (double)count / bandH;
            }

            var gridSegs = SignalProcessing.FindDarkDensitySegments(darkDensity, gridSegThresh, 200);

            foreach (var (segLeft, segRight) in gridSegs)
            {
                int segLen = segRight - segLeft;
                double[] segment = new double[segLen];
                Array.Copy(darkDensity, segLeft, segment, 0, segLen);

                var (period, acScore) = SignalProcessing.FindPeriodWithScore(segment, minCellSize, maxCellSize);
                if (period <= 0) continue;

                var (extLeft, extRight) = SignalProcessing.FindGridExtent(segment, period);
                if (extLeft < 0) continue;

                int absLeft = segLeft + extLeft;
                int absRight = segLeft + extRight;
                int extent = absRight - absLeft;

                if (extent < period * 8 || extent < 200) continue;

                candidates.Add((by, period, acScore, absLeft, absRight));
            }
        }

        candidates.Sort((a, b) =>
        {
            double sa = a.hAc * (a.hRight - a.hLeft);
            double sb = b.hAc * (b.hRight - b.hLeft);
            return sb.CompareTo(sa);
        });

        // Pass 2: Verify vertical periodicity
        foreach (var cand in candidates.Take(10))
        {
            int colSpan = cand.hRight - cand.hLeft;
            if (colSpan < cand.cellW * 3) continue;

            double[] rowDensity = new double[h];
            for (int y = 0; y < h; y++)
            {
                int count = 0;
                for (int x = cand.hLeft; x < cand.hRight; x++)
                {
                    if (gray[y * w + x] < veryDarkPixelThresh) count++;
                }
                rowDensity[y] = (double)count / colSpan;
            }

            var vGridSegs = SignalProcessing.FindDarkDensitySegments(rowDensity, gridSegThresh, 100);
            if (vGridSegs.Count == 0) continue;

            var (vSegTop, vSegBottom) = vGridSegs.OrderByDescending(s => s.end - s.start).First();
            int vSegLen = vSegBottom - vSegTop;
            double[] vSegment = new double[vSegLen];
            Array.Copy(rowDensity, vSegTop, vSegment, 0, vSegLen);

            var (cellH, vAc) = SignalProcessing.FindPeriodWithScore(vSegment, minCellSize, maxCellSize);
            if (cellH <= 0) continue;

            var (extTop, extBottom) = SignalProcessing.FindGridExtent(vSegment, cellH);
            if (extTop < 0) continue;

            int top = vSegTop + extTop;
            int bottom = vSegTop + extBottom;
            int vExtent = bottom - top;

            if (vExtent < cellH * 3 || vExtent < 100) continue;

            int gridW = cand.hRight - cand.hLeft;
            int gridH = bottom - top;
            int cols = Math.Max(2, (int)Math.Round((double)gridW / cand.cellW));
            int rows = Math.Max(2, (int)Math.Round((double)gridH / cellH));

            gridW = cols * cand.cellW;
            gridH = rows * cellH;

            return new DetectGridResult
            {
                Detected = true,
                Region = new Region(region.X + cand.hLeft, region.Y + top, gridW, gridH),
                Cols = cols,
                Rows = rows,
                CellWidth = Math.Round((double)gridW / cols, 1),
                CellHeight = Math.Round((double)gridH / rows, 1),
            };
        }

        return new DetectGridResult { Detected = false };
    }
}

public class DetectGridResult
{
    public bool Detected { get; set; }
    public Region? Region { get; set; }
    public int Cols { get; set; }
    public int Rows { get; set; }
    public double CellWidth { get; set; }
    public double CellHeight { get; set; }
}