DigitalImageProcessing/DigitalImageProcessing/Segmentation.cs

namespace DigitalImageProcessing
{
    internal static class Segmentation
    {
        private const float _0 = 1e-6f;
        public static void Run1(int thresholdDelta)
        {
            int thresholdValue = 128;

            float delta = float.MaxValue;
            int loopCount = 0;

            int[,] grayImage = GLobalTools.GetGrayAsArray(@"C:\Users\Surface\Downloads\Sprite-0001.png");

            while (delta > thresholdDelta)
            {
                loopCount++;
                List<int> forePix = [], backPix = [];
                for (int i = 0; i < grayImage.GetLength(0); i++)
                    for (int j = 0; j < grayImage.GetLength(1); j++)
                        if (grayImage[i, j] >= thresholdValue)
                            forePix.Add(grayImage[i, j]);
                        else
                            backPix.Add(grayImage[i, j]);
                int fore = (int)forePix.Average();
                int back = (int)backPix.Average();
                int thres = (fore + back) / 2;
                delta = int.Abs(thres - thresholdValue);
                thresholdValue = thres;
                Console.WriteLine($"Current Threshold Value: {thres}, Delta: {delta}");
            }
            Console.WriteLine($"Threshold Value: {thresholdValue} found in {loopCount} loops.");
            int[,] foreground = grayImage.Select(i => i > thresholdValue ? 255 : 0);
            foreground.Save(@"C:\Users\Surface\Downloads\OIP_foreground.webp");
        }
        public static void Run2()
        {
            int[,] gray = GLobalTools.GetGrayAsArray(@"C:\Users\Surface\Downloads\Sprite-0001.png");
            int[] pixels = new int[254];
            int size = 0;


            for (int i = 0; i < gray.GetLength(0); i++)
                for (int j = 0; j < gray.GetLength(1); j++)
                    if (gray[i, j] is > 0 and < 255)
                    {
                        pixels[gray[i, j] - 1]++;
                        size++;
                    }

            float[] pws = new float[pixels.Length]; // 类概率
            int mut = 0;
            for (int t = 0; t < pixels.Length; t++)
            {
                pws[t] = (float)pixels[t] / size;
                mut += t * pixels[t];
            }

            float w0 = 0; // 类内概率
            float mu0 = 0; // 类内均值
            float wxmax = 0; // 类间方差最大值
            int threshold = 0;
            for (int t = 0; t < pixels.Length; t++)
            {
                w0 += pws[t];
                mu0 += t * pws[t];
                float w1 = 1 - w0;
                if (w0 < _0 || w1 < _0) continue;
                float mu1 = (mut - mu0) / w1;
                mu0 /= w0;
                float wx = w0 * w1 * (mu0 / w0 - mu1) * (mu0 / w0 - mu1);
                if (wx > wxmax)
                {
                    wxmax = wx;
                    threshold = t + 1;
                }
            }
            Console.WriteLine($"Threshold Value: {threshold}");
            int[,] foreground = gray.Select(i => i > threshold ? 255 : 0);
            foreground.Save(@"C:\Users\Surface\Downloads\OIP_foreground.webp");
        }
    }
}