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 static class Renderer
{
    private const int ImageMaxSize = 20000;
    private const float PenThickness = 4;

    public class Bounds
    {
        public readonly float minLat, maxLat, minLon, maxLon;

        public Bounds(float minLat, float minLon, float maxLat, float maxLon)
        {
            this.minLon = minLon;
            this.maxLat = maxLat;
            this.maxLon = maxLon;
            this.minLat = minLat;
        }
    }

    [SuppressMessage("Interoperability", "CA1416:Plattformkompatibilität überprüfen")]
    public static void DrawGraph(string resultPath, Image? area = null, Bounds? bounds = null)
    {
        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;

        Image renderedImage = DrawLoadedNodes(graph.gScoreNodes!, graph.gScore!, coords, area, bounds);
        renderedImage.Save($"{workingDir}-routing.png");
    }

    [SuppressMessage("Interoperability", "CA1416:Plattformkompatibilität überprüfen")]
    public static ValueTuple<Image, Bounds> DrawArea(RegionManager rm)
    {
        HashSet<OsmNode> nodes = new HashSet<OsmNode>();
        foreach (OSMDatastructure.Region r in rm.GetAllRegions())
            nodes = nodes.Concat(r.nodes).ToHashSet();

        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);

        float latDiff = maxLat - minLat;
        float lonDiff = maxLon - minLon;

        float scaleFactor = latDiff > lonDiff ? ImageMaxSize / latDiff : ImageMaxSize / lonDiff;

        int pixelsX = (int)(lonDiff * scaleFactor);
        int pixelsY = (int)(latDiff * scaleFactor);
        
        Image ret = new Bitmap(pixelsX, pixelsY, PixelFormat.Format32bppRgb);
        Graphics g = Graphics.FromImage(ret);
        g.Clear(Color.White);

        Color start = Color.FromArgb(255, 25, 25, 25);
        Color center = Color.FromArgb(255, 0, 0, 0);
        Color end = Color.FromArgb(255, 0, 255, 0);

        foreach (OsmNode node in nodes)
        {
            foreach (OsmEdge edge in node.edges)
            {
                Coordinates c1 = node.coordinates;
                OsmNode nNode = rm.GetNode(edge.neighborId, edge.neighborRegion)!;
                Coordinates c2 = nNode.coordinates;

                Pen p = new Pen(GradientPick(0, start, center, end), PenThickness);
                float x1 = (c1.longitude - minLon) * scaleFactor;
                float y1 = (maxLat - c1.latitude) * scaleFactor;
                float x2 = (c2.longitude - minLon) * scaleFactor;
                float y2 = (maxLat - c2.latitude) * scaleFactor;
                
                g.DrawLine(p, x1, y1, x2, y2);
            }
        }

        return new ValueTuple<Image, Bounds>(ret, new Bounds(minLat,minLon,maxLat,maxLon));
    }

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

        float scaleFactor = latDiff > lonDiff ? ImageMaxSize / latDiff : ImageMaxSize / lonDiff;

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

        Image ret;
        Graphics g;
        if (renderOver is null)
        {
            ret = new Bitmap(pixelsX, pixelsY, PixelFormat.Format32bppRgb);
            g = Graphics.FromImage(ret);
            g.Clear(Color.White);
        }
        else
        {
            ret = renderOver;
            g = Graphics.FromImage(ret);
        }

        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;

            x -= (PenThickness * 1.5f) / 2;
            y -= (PenThickness * 1.5f) / 2;
            g.FillEllipse(b, x, y, PenThickness * 1.5f, PenThickness * 1.5f);
        }
        
        Pen p = new Pen(Color.Red, PenThickness);

        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);
        }

        return ret;
    }
    
    /*
     * 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);
    }
}