OpenCvSharp で色領域抽出 (C++ API で)

ColorExtraction.cs

using OpenCvSharp;
using OpenCvSharp.CPlusPlus;
using System;

namespace OpenCvSharpSample
{
    class Program
    {
        static void Main(string[] args)
        {
            // ファイル読み込み
            var mat = new Mat("lena.jpg");
            
            // 肌色領域を抽出
            var skinMat = ColorExtraction(mat, ColorConversion.BgrToHsv, 0, 10, 80, 255, 0, 255);

            Cv2.ImShow("SrcMat", mat);
            Cv2.ImShow("SkinColor", skinMat);
            Cv2.WaitKey(0);
        }

        // OpenCvSharp3　では ColorConversionCodes
        public static Mat ColorExtraction(Mat srcMat, ColorConversion code,
        int ch1Lower, int ch1Upper,
        int ch2Lower, int ch2Upper,
        int ch3Lower, int ch3Upper)
        {
            if (srcMat == null)
                throw new ArgumentNullException("srcMat");

            var colorMat = srcMat.CvtColor(code);

            var lut = new Mat(256, 1, MatType.CV_8UC3);

            var lower = new int[3] { ch1Lower, ch2Lower, ch3Lower };
            var upper = new int[3] { ch1Upper, ch2Upper, ch3Upper };

            // cv::Mat_<cv::Vec3b>
            var mat3 = new MatOfByte3(lut);

            var indexer = mat3.GetIndexer();

            for (int i = 0; i < 256; i++)
            {
                var color = indexer[i];
                byte temp;

                for (int k = 0; k < 3; k++)
                {

                    if (lower[k] <= upper[k])
                    {
                        if ((lower[k] <= i) && (i <= upper[k]))
                        {
                            temp = 255;
                        }
                        else
                        {
                            temp = 0;
                        }
                    }
                    else
                    {
                        if ((i <= upper[k]) || (lower[k] <= i))
                        {
                            temp = 255;
                        }
                        else
                        {
                            temp = 0;
                        }
                    }

                    color[k] = temp;
                }

                indexer[i] = color;
            }

            Cv2.LUT(colorMat, lut, colorMat);

            var channelMat = colorMat.Split();

            var maskMat = new Mat();

            Cv2.BitwiseAnd(channelMat[0], channelMat[1], maskMat);
            Cv2.BitwiseAnd(maskMat, channelMat[2], maskMat);

            srcMat.CopyTo(maskMat, maskMat);

            return maskMat;
        }
    }
}