IPCALLServicePro/HNWD.Pregrant.Common/BitmapGray.cs

using System.Drawing;

namespace HNWD.Pregrant.Common
{
    public class BitmapGray
    {
        public 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);
                    //计算灰度值
                    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);
                }
            }
        }

        public static void Thresholding(Bitmap img1)
        {
            int[] histogram = new int[256];
            int minGrayValue = 255, maxGrayValue = 0;
            //求取直方图
            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;
                }
            }
            //迭代计算阀值
            int threshold = -1;
            int newThreshold = (minGrayValue + maxGrayValue) / 2;
            for (int iterationTimes = 0; threshold != newThreshold && iterationTimes < 255; iterationTimes++)
            {
                threshold = newThreshold;
                int lP1 = 0;
                int lP2 = 0;
                int lS1 = 0;
                int lS2 = 0;
                //求两个区域的灰度的平均值
                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 = 0;

                if (lS2 != 0)
                {
                    mean2GrayValue = (lP2 / lS2);
                }

                newThreshold = (mean1GrayValue + mean2GrayValue) / 2;
            }
            //计算二值化
            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));
                }
            }
        }
    }
}