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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);
//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);
}
}
}
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 < 100; 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 = (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));
}
}
}
static void Main(string[] args)
{
try
{
//打开位图文件
Bitmap img1 = new Bitmap("test.jpg", true);
//灰度化
ToGrey(img1);
//二值化
Thresholding(img1);
//写回位图文件
img1.Save("output.jpg");
Console.WriteLine("Converted.");
}
catch (ArgumentException)
{
Console.WriteLine("Invalid usage!");
Console.WriteLine("Usage: bmp2grey source object");
}
}
}
}
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