OSMServer/RenderPath/Renderer.cs

using System.Diagnostics.CodeAnalysis;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text.Json;
using OSMDatastructure.Graph;
using Pathfinding;

namespace RenderPath;

public class Renderer
{

    public static void DrawGraph(string resultPath)
    {
        FileStream fs = new FileStream(resultPath, FileMode.Open);
        PathResult graph = JsonSerializer.Deserialize<PathResult>(fs)!;
        List<Coordinates> coords = new List<Coordinates>();
        foreach (PathNode node in graph.pathNodes)
            coords.Add(node.coordinates);
        string workingDir = new DirectoryInfo(resultPath).FullName;

        DrawLoadedNodes(graph.nodes!, graph.gScore!, coords, workingDir);
    }

    [SuppressMessage("Interoperability", "CA1416:Plattformkompatibilität überprüfen")]
    public static void DrawLoadedNodes(HashSet<OsmNode> nodes, Dictionary<ulong, double> gScoreDict, List<Coordinates> pathCoordinates, string workingDir)
    {
        float minLat = nodes.Min(node => node.coordinates.latitude);
        float minLon = nodes.Min(node => node.coordinates.longitude);
        float maxLat = nodes.Max(node => node.coordinates.latitude);
        float maxLon = nodes.Max(node => node.coordinates.longitude);

        double minWeight = gScoreDict.Min(kv => kv.Value);
        double maxWeight = gScoreDict.Max(kv => kv.Value);
        
        float latDiff = maxLat - minLat;
        float lonDiff = maxLon - minLon;

        const int imageMaxSize = 10000;
        float scaleFactor = latDiff > lonDiff ? imageMaxSize / latDiff : imageMaxSize / lonDiff;

        int pixelsX = (int)(lonDiff * scaleFactor);
        int pixelsY = (int)(latDiff * scaleFactor);

        Bitmap ret = new Bitmap(pixelsX, pixelsY, PixelFormat.Format32bppRgb);
        Graphics g = Graphics.FromImage(ret);
        g.Clear(Color.White);

        Color start = Color.FromArgb(0, 0, 255);
        Color center = Color.FromArgb(255, 255, 0);
        Color end = Color.FromArgb(0, 255, 0);

        foreach (KeyValuePair<ulong, double> kv in gScoreDict)
        {
            double percentage = (kv.Value - minWeight) / (maxWeight - minWeight);
            Brush b = new SolidBrush(GradientPick(percentage, start, center, end));
            OsmNode node = nodes.First(node => node.nodeId.Equals(kv.Key));
            
            float x = (node.coordinates.longitude - minLon) * scaleFactor;
            float y = (maxLat - node.coordinates.latitude) * scaleFactor;
            g.FillEllipse(b, x, y, 2, 2);
        }
        
        Pen p = new Pen(Color.Red, 2);

        for (int i = 0; i < pathCoordinates.Count - 1; i++)
        {
            Coordinates c1 = pathCoordinates[i];
            Coordinates c2 = pathCoordinates[i+1];
            Point p1 = new(Convert.ToInt32((c1.longitude - minLon) * scaleFactor), Convert.ToInt32((maxLat - c1.latitude) * scaleFactor));
            Point p2 = new(Convert.ToInt32((c2.longitude - minLon) * scaleFactor), Convert.ToInt32((maxLat - c2.latitude) * scaleFactor));
            g.DrawLine(p, p1, p2);
        }
        
        ret.Save($"{workingDir}-routing.png", ImageFormat.Bmp);
    }
    
    /*
     * https://stackoverflow.com/questions/55601338/get-a-color-value-within-a-gradient-based-on-a-value
     */
    private static int LinearInterp(int start, int end, double percentage) => start + (int)Math.Round(percentage * (end - start));
    private static Color ColorInterp(Color start, Color end, double percentage) =>
        Color.FromArgb(LinearInterp(start.A, end.A, percentage),
            LinearInterp(start.R, end.R, percentage),
            LinearInterp(start.G, end.G, percentage),
            LinearInterp(start.B, end.B, percentage));
    private static Color GradientPick(double percentage, Color Start, Color Center, Color End) {
        if (percentage < 0.5)
            return ColorInterp(Start, Center, percentage / 0.5);
        else if (percentage == 0.5)
            return Center;
        else
            return ColorInterp(Center, End, (percentage - 0.5)/0.5);
    }
}