UVtools/UVtools.Core/EmguCV/EmguContours.cs

/*
 *                     GNU AFFERO GENERAL PUBLIC LICENSE
 *                       Version 3, 19 November 2007
 *  Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 *  Everyone is permitted to copy and distribute verbatim copies
 *  of this license document, but changing it is not allowed.
 */

using System;
using System.Collections;
using Emgu.CV;
using Emgu.CV.Util;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Threading.Tasks;
using Emgu.CV.CvEnum;
using UVtools.Core.Extensions;

namespace UVtools.Core.EmguCV;

/// <summary>
/// Utility methods for contour handling.  
/// Use only with Tree type
/// </summary>
public class EmguContours : IReadOnlyList<EmguContour>, IDisposable
{
    private readonly EmguContour[] _contours;

    public IEnumerator<EmguContour> GetEnumerator()
    {
        return ((IEnumerable<EmguContour>)_contours).GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return _contours.GetEnumerator();
    }

    public int Count => _contours.Length;

    public readonly int[,] Hierarchy = new int[0,0];


    public EmguContour this[int index] => _contours[index];

    public EmguContours(VectorOfVectorOfPoint vectorOfPointsOfPoints)
    {
        _contours = new EmguContour[vectorOfPointsOfPoints.Size];
        for (int i = 0; i < _contours.Length; i++)
        {
            _contours[i] = new EmguContour(vectorOfPointsOfPoints[i]);
        }
    }

    public EmguContours(VectorOfVectorOfPoint vectorOfPointsOfPoints, int[,] hierarchy) : this(vectorOfPointsOfPoints)
    {
        Hierarchy = hierarchy;
    }

    public EmguContours(IInputOutputArray mat, RetrType mode = RetrType.List, ChainApproxMethod method = ChainApproxMethod.ChainApproxSimple, Point offset = default)
    {
        using var contours = mat.FindContours(out Hierarchy, mode, method, offset);
        _contours = new EmguContour[contours.Size];
        for (int i = 0; i < _contours.Length; i++)
        {
            _contours[i] = new EmguContour(contours[i]);
        }
    }

    public (int Index, EmguContour Contour, double Distance)[][] CalculateCentroidDistances(bool includeOwn = false, bool sortByDistance = true)
    {
        var items = new (int Index, EmguContour Contour, double Distance)[Count][];
        for (int i = 0; i < Count; i++)
        {
            items[i] = new (int Index, EmguContour Contour, double Distance)[Count-1];
            int count = 0;
            for (int x = 0; x < Count; x++)
            {
                if (x == i)
                {
                    if (includeOwn)
                    {
                        items[i][count] = new(x, this[x], 0);
                    }
                    continue;
                }
                items[i][count] = new (x, this[x], PointExtensions.FindLength(this[i].Centroid, this[x].Centroid));

                count++;
            }

            if(sortByDistance) items[i] = items[i].OrderBy(tuple => tuple.Distance).ToArray();
        }

        return items;
    }

    public void Dispose()
    {
        foreach (var contour in _contours)
        {
            contour.Dispose();
        }
    }

    /// <summary>
    /// Gets contours inside a point
    /// </summary>
    /// <param name="contours"></param>
    /// <param name="hierarchy"></param>
    /// <param name="location"></param>
    /// <param name="includeLimitingArea">If true it will include all limiting area, otherwise only outer contour will be returned</param>
    /// <returns></returns>
    public static VectorOfVectorOfPoint GetContoursInside(VectorOfVectorOfPoint contours, int[,] hierarchy, Point location, bool includeLimitingArea = true)
    {
        var vector = new VectorOfVectorOfPoint();
        var vectorSize = contours.Size;
        for (var i = vectorSize - 1; i >= 0; i--)
        {
            if (CvInvoke.PointPolygonTest(contours[i], location, false) < 0) continue;
            vector.Push(contours[i]);
            if (!includeLimitingArea) break;
            for (int n = i + 1; n < vectorSize; n++)
            {
                if (hierarchy[n, EmguContour.HierarchyParent] != i) continue;
                vector.Push(contours[n]);
            }
            break;
        }

        return vector;
    }

    /// <summary>
    /// Gets a contour given a location.
    /// </summary>
    /// <param name="contours"></param>
    /// <param name="location"></param>
    /// <param name="index">Contour index, -1 if not exists</param>
    /// <returns>null if not exists</returns>
    public static VectorOfPoint? GetContourInside(VectorOfVectorOfPoint contours, Point location, out int index)
    {
        index = -1;
        var vectorSize = contours.Size;
        for (int i = vectorSize - 1; i >= 0; i--)
        {
            if (CvInvoke.PointPolygonTest(contours[i], location, false) < 0) continue;
            index = i;
            return contours[i];
        }

        return null;
    }

    /// <summary>
    /// Gets only the outer most external contours
    /// Only compatible with Tree type of contour detection
    /// </summary>
    /// <param name="contours"></param>
    /// <param name="hierarchy"></param>
    /// <returns></returns>
    public static VectorOfVectorOfPoint GetExternalContours(VectorOfVectorOfPoint contours, int[,] hierarchy)
    {
        var result = new VectorOfVectorOfPoint();
        var vectorSize = contours.Size;
        for (var i = 0; i < vectorSize; i++)
        {
            if (hierarchy[i, EmguContour.HierarchyParent] != -1) continue;
            result.Push(contours[i]);
        }

        return result;
    }

    /// <summary>
    /// Gets contours inside contours that are black pixels
    /// </summary>
    /// <param name="contours"></param>
    /// <param name="hierarchy"></param>
    /// <returns></returns>
    public static VectorOfVectorOfPoint GetNegativeContours(VectorOfVectorOfPoint contours, int[,] hierarchy)
    {
        var result = new VectorOfVectorOfPoint();
        var vectorSize = contours.Size;
        for (var i = 0; i < vectorSize; i++)
        {
            if (hierarchy[i, EmguContour.HierarchyParent] == -1) continue;
            result.Push(contours[i]);
        }

        return result;
    }

    /// <summary>
    /// Gets contours that are positive and negative pixels and group them by areas
    /// Only compatible with Tree type of contour detection
    /// </summary>
    /// <returns></returns>
    public static List<VectorOfVectorOfPoint>[] GetContoursInGroups(VectorOfVectorOfPoint contours, int[,] hierarchy)
    {
        return new []{GetPositiveContoursInGroups(contours, hierarchy), GetNegativeContoursInGroups(contours, hierarchy)};
    }

    /// <summary>
    /// Gets contours that are positive pixels and group them by areas
    /// Only compatible with Tree type of contour detection
    /// </summary>
    /// <returns></returns>
    public static List<VectorOfVectorOfPoint> GetPositiveContoursInGroups(VectorOfVectorOfPoint contours, int[,] hierarchy)
    {
        var result = new List<VectorOfVectorOfPoint>();
        var vectorSize = contours.Size;
        var processedContours = new bool[vectorSize];
        for (int i = 0; i < vectorSize; i++)
        {
            if (processedContours[i]) continue;
            processedContours[i] = true;
            var index = result.Count;
            result.Add(new VectorOfVectorOfPoint(contours[i]));
            for (int n = i + 1; n < vectorSize; n++)
            {
                if (processedContours[n] || hierarchy[n, EmguContour.HierarchyParent] != i) continue;
                processedContours[n] = true;
                result[index].Push(contours[n]);
            }
        }

        return result;
    }

    /// <summary>
    /// Gets contours inside contours that are black pixels and group them by areas
    /// Only compatible with Tree type of contour detection
    /// </summary>
    /// <returns></returns>
    public static List<VectorOfVectorOfPoint> GetNegativeContoursInGroups(VectorOfVectorOfPoint contours, int[,] hierarchy)
    {
        var result = new List<VectorOfVectorOfPoint>();
        var vectorSize = contours.Size;
        var processedContours = new bool[vectorSize];
        for (int i = 0; i < vectorSize; i++)
        {
            if (processedContours[i]) continue;
            processedContours[i] = true;
            if (hierarchy[i, EmguContour.HierarchyParent] == -1) continue;
            var index = result.Count;
            result.Add(new VectorOfVectorOfPoint(contours[i]));
            for (int n = i + 1; n < vectorSize; n++)
            {
                if (processedContours[n] || hierarchy[n, EmguContour.HierarchyParent] != i) continue;
                processedContours[n] = true;
                result[index].Push(contours[n]);
            }
        }

        return result;
    }

    /// <summary>
    /// Gets contour real area for a limited area
    /// </summary>
    /// <param name="contours"></param>
    /// <returns></returns>
    public static double GetContourArea(VectorOfVectorOfPoint contours)
    {
        var vectorSize = contours.Size;
        if (vectorSize == 0) return 0;

        double result = CvInvoke.ContourArea(contours[0]);
        for (var i = 1; i < vectorSize; i++)
        {
            result -= CvInvoke.ContourArea(contours[i]);
        }
        return result;
    }

    /// <summary>
    /// Gets the largest contour area from a contour list
    /// </summary>
    /// <param name="contours">Contour list</param>
    /// <returns></returns>
    public static double GetLargestContourArea(VectorOfVectorOfPoint contours)
    {
        var vectorSize = contours.Size;
        if (vectorSize == 0) return 0;

        double result = 0;
        for (var i = 0; i < vectorSize; i++)
        {
            result = Math.Max(result, CvInvoke.ContourArea(contours[i]));
        }
        return result;
    }

    /// <summary>
    /// Gets contours real area for a group of contours
    /// </summary>
    /// <param name="contours">Grouped contours</param>
    /// <param name="useParallel">True to run in parallel</param>
    /// <returns>Array with same size with contours area</returns>
    public static double[] GetContoursArea(List<VectorOfVectorOfPoint> contours, bool useParallel = false)
    {
        var result = new double[contours.Count];

        if (useParallel)
        {
            Parallel.For(0, contours.Count, CoreSettings.ParallelOptions, i =>
            {
                result[i] = GetContourArea(contours[i]);
            });
        }
        else
        {
            for (var i = 0; i < contours.Count; i++)
            {
                result[i] = GetContourArea(contours[i]);
            }
        }
            
        return result;
    }

    /// <summary>
    /// Checks if two contours intersects and return the intersecting pixel count
    /// </summary>
    /// <param name="contour1">Contour 1</param>
    /// <param name="contour2">Contour 2</param>
    /// <returns>Intersecting pixel count</returns>
    public static int ContoursIntersectingPixels(VectorOfVectorOfPoint contour1, VectorOfVectorOfPoint contour2)
    {
        var contour1Rect = CvInvoke.BoundingRectangle(contour1[0]);
        var contour2Rect = CvInvoke.BoundingRectangle(contour2[0]);

        /* early exit if the bounding rectangles don't intersect */
        if (!contour1Rect.IntersectsWith(contour2Rect)) return 0;
        var totalRect = Rectangle.Union(contour1Rect, contour2Rect);

        using var contour1Mat = EmguExtensions.InitMat(totalRect.Size);
        using var contour2Mat = EmguExtensions.InitMat(totalRect.Size);

        var inverseOffset = new Point(-totalRect.X, -totalRect.Y);
        CvInvoke.DrawContours(contour1Mat, contour1, -1, EmguExtensions.WhiteColor, -1, LineType.EightConnected, null, int.MaxValue, inverseOffset);
        CvInvoke.DrawContours(contour2Mat, contour2, -1, EmguExtensions.WhiteColor, -1, LineType.EightConnected, null, int.MaxValue, inverseOffset);

        CvInvoke.BitwiseAnd(contour1Mat, contour2Mat, contour1Mat);

        return CvInvoke.CountNonZero(contour1Mat);
    }

    /// <summary>
    /// Checks if two contours intersects
    /// </summary>
    /// <param name="contour1">Contour 1</param>
    /// <param name="contour2">Contour 2</param>
    /// <returns></returns>
    public static bool ContoursIntersect(VectorOfVectorOfPoint contour1, VectorOfVectorOfPoint contour2)
    {
        return ContoursIntersectingPixels(contour1, contour2) > 0;
    }
}