OSMServer/RenderPath/Renderer.cs

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

namespace RenderPath;

public static class Renderer
{
    private const int ImageMaxSize = 20000;
    private const float PenThickness = 4;
    private static readonly Color RouteColor = Color.Red;
    private static readonly Color WeightStartColor = Color.FromArgb(0, 0, 255);
    private static readonly Color WeightCenterColor = Color.FromArgb(255, 255, 0);
    private static readonly Color WeightEndColor = Color.FromArgb(0, 255, 0);

    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 Image DrawPathfinder(Pathfinder pathfinder)
    {
        Console.WriteLine("Rendering loaded Regions");
        ValueTuple<Image, Bounds> areaRender = DrawArea(pathfinder.regionManager);
        Console.WriteLine("Rendering gScores (Weights)");
        ValueTuple<Image, Bounds> areaGScoreRender = DrawGScores(pathfinder.gScore!, areaRender.Item1, areaRender.Item2);
        Console.WriteLine("Rendering path");
        ValueTuple<Image, Bounds> areaGScorePathRender = DrawPath(pathfinder.pathResult!, areaGScoreRender.Item1, areaGScoreRender.Item2);

        return areaGScorePathRender.Item1;
    }

    [SuppressMessage("Interoperability", "CA1416:Plattformkompatibilität überprüfen")]
    public static ValueTuple<Image, Bounds> DrawArea(RegionManager rm)
    {
        HashSet<OsmNode> nodes = new();
        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);

        //TODO Use road priority for roadcolor
        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(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 ValueTuple<Image, Bounds> DrawPath(PathResult pathResult, Image? renderOver = null, Bounds? bounds = null)
    {
        List<Coordinates> coordinates = new();
        foreach(PathNode node in pathResult.pathNodes)
            coordinates.Add(node.coordinates);
        
        float minLat = bounds?.minLat ?? coordinates.Min(coords => coords.latitude);
        float minLon = bounds?.minLon ?? coordinates.Min(coords => coords.longitude);
        float maxLat = bounds?.maxLat ?? coordinates.Max(coords => coords.latitude);
        float maxLon = bounds?.maxLon ?? coordinates.Max(coords => coords.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 = renderOver ?? new Bitmap(pixelsX, pixelsY, PixelFormat.Format32bppRgb);
        Graphics g = Graphics.FromImage(ret);
        if(renderOver is null)
            g.Clear(Color.White);

        Pen p = new Pen(RouteColor, PenThickness);

        for (int i = 0; i < coordinates.Count - 1; i++)
        {
            Coordinates c1 = coordinates[i];
            Coordinates c2 = coordinates[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 new ValueTuple<Image, Bounds>(ret, new Bounds(minLat,minLon,maxLat,maxLon));
    }

    [SuppressMessage("Interoperability", "CA1416:Plattformkompatibilität überprüfen")]
    public static ValueTuple<Image, Bounds> DrawGScores(Dictionary<OsmNode, double> gScoreDict, Image? renderOver = null,
        Bounds? bounds = null)
    {
        float minLat = bounds?.minLat ?? gScoreDict.Min(kv => kv.Key.coordinates.latitude);
        float minLon = bounds?.minLon ?? gScoreDict.Min(kv => kv.Key.coordinates.longitude);
        float maxLat = bounds?.maxLat ?? gScoreDict.Max(kv => kv.Key.coordinates.latitude);
        float maxLon = bounds?.maxLon ?? gScoreDict.Max(kv => kv.Key.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 = renderOver ?? new Bitmap(pixelsX, pixelsY, PixelFormat.Format32bppRgb);
        Graphics g = Graphics.FromImage(ret);
        if(renderOver is null)
            g.Clear(Color.White);
        
        foreach (KeyValuePair<OsmNode, double> kv in gScoreDict)
        {
            double percentage = (kv.Value - minWeight) / (maxWeight - minWeight);
            Brush b = new SolidBrush(GradientPick(percentage, WeightStartColor, WeightCenterColor, WeightEndColor));
            
            float x = (kv.Key.coordinates.longitude - minLon) * scaleFactor;
            float y = (maxLat - kv.Key.coordinates.latitude) * scaleFactor;

            x -= (PenThickness * 1.5f) / 2;
            y -= (PenThickness * 1.5f) / 2;
            g.FillEllipse(b, x, y, PenThickness * 1.5f, PenThickness * 1.5f);
        }

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

    /*
     * 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);
    }
}