using System;using System.Drawing;namespace BMP2Grey{  class Program  {    static void ToGrey(Bitmap img1)    {      for (int i = 0; i < img1.Width; i++)      {        for (int j = 0; j < img1.Height; j++)        {          Color pixelColor = img1.GetPixel(i, j);          //計算灰度值          int grey = (int)(0.299 * pixelColor.R + 0.587 * pixelColor.G + 0.114 * pixelColor.B);          Color newColor = Color.FromArgb(grey, grey, grey);          img1.SetPixel(i, j, newColor);        }      }    }    static void Thresholding(Bitmap img1)    {      int[] histogram = new int[256];      int minGrayValue=255, maxGrayValue=0;      //求取直方圖      for (int i = 0; i < img1.Width; i++)      {        for (int j = 0; j < img1.Height; j++)        {          Color pixelColor = img1.GetPixel(i, j);          histogram[pixelColor.R]++;          if (pixelColor.R > maxGrayValue) maxGrayValue = pixelColor.R;          if (pixelColor.R < minGrayValue) minGrayValue = pixelColor.R;        }      }      //迭代計算閥值      int threshold = -1;      int newThreshold = (minGrayValue + maxGrayValue) / 2;      for(int iterationTimes = 0; threshold != newThreshold && iterationTimes < 100; iterationTimes++)      {        threshold = newThreshold;        int lP1 =0;        int lP2 =0;        int lS1 = 0;        int lS2 = 0;        //求兩個區域的灰度的平均值        for (int i = minGrayValue;i < threshold;i++)        {          lP1 += histogram[i] * i;          lS1 += histogram[i];        }        int mean1GrayValue = (lP1 / lS1);        for (int i = threshold+1;i < maxGrayValue;i++)        {          lP2 += histogram[i] * i;          lS2 += histogram[i];        }        int mean2GrayValue = (lP2 / lS2);        newThreshold = (mean1GrayValue + mean2GrayValue) / 2;      }      //計算二值化      for (int i = 0; i < img1.Width; i++)      {        for (int j = 0; j < img1.Height; j++)        {          Color pixelColor = img1.GetPixel(i, j);          if (pixelColor.R > threshold) img1.SetPixel(i, j, Color.FromArgb(255, 255, 255));          else img1.SetPixel(i, j, Color.FromArgb(0, 0, 0));        }      }    }    static void Main(string[] args)    {      try      {        //打開位圖文件        Bitmap img1 = new Bitmap("test.jpg", true);        //灰度化        ToGrey(img1);        //二值化        Thresholding(img1);        //寫回位圖文件        img1.Save("output.jpg");        Console.WriteLine("Converted.");      }      catch (ArgumentException)      {        Console.WriteLine("Invalid usage!");        Console.WriteLine("Usage: bmp2grey source object");      }    }  }}