转自：https://www.cnblogs.com/dearzhoubi/p/8622325.html

灰度图像的点运算可分为线性点运算和非线性点运算两种。
4.1线性点运算定义
线性点运算就是输出灰度级与输入灰度级呈线性关系的点运算。在这种情况下,灰度变换函数的形式为:

g(x, y)=pf(x,y)+L

其中 f(x,y) 为输入图像在点 (x,y) 的灰度值, g(x,y) 为相应的输出点的灰度值。显然,如果P=1和L=0,g(x,y)就是f(x,y)的复制;如果P<1,输出图像的对比度将增大;如果P>1,则对比度将减少;如果P=1而L≠0,该操作仅使所有像素的灰度值上移或下移,其效果是使整个图像在显示时更暗或更亮;如果P为负值,暗区域将变亮,亮区域将变暗,该操作完成了图像求补。

 

linearPOForm.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;namespace histogram
{public partial class linearPOForm : Form{public linearPOForm(){InitializeComponent();}private void startLinear_Click(object sender, EventArgs e){//设置DialogResult属性this.DialogResult = DialogResult.OK;}private void close_Click(object sender, EventArgs e){this.Close();}//设置两个get访问器public string GetScaling{get{//得到斜率return scaling.Text;}}public string GetOffset{get{//得到偏移量return offset.Text;}}}
}

Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;namespace histogram
{public partial class Form1 : Form{public Form1(){InitializeComponent();}//文件名private string curFileName;//图像对象private System.Drawing.Bitmap curBitmpap;/// <summary>/// 打开图像文件/// </summary>private void open_Click(object sender, EventArgs e){//创建OpenFileDialogOpenFileDialog opnDlg = new OpenFileDialog();//为图像选择一个筛选器opnDlg.Filter = "所有图像文件|*.bmp;*.pcx;*.png;*.jpg;*.gif;" +"*.tif;*.ico;*.dxf;*.cgm;*.cdr;*.wmf;*.eps;*.emf|" +"位图(*.bmp;*.jpg;*.png;...)|*.bmp;*.pcx;*.png;*.jpg;*.gif;*.tif;*.ico|" +"矢量图(*.wmf;*.eps;*.emf;...)|*.dxf;*.cgm;*.cdr;*.wmf;*.eps;*.emf";//设置对话框标题opnDlg.Title = "打开图像文件";//启用“帮助”按钮opnDlg.ShowHelp = true;//如果结果为“打开”，选定文件if (opnDlg.ShowDialog() == DialogResult.OK){//读取当前选中的文件名curFileName = opnDlg.FileName;//使用Image.FromFile创建图像对象try{curBitmpap = (Bitmap)Image.FromFile(curFileName);}catch (Exception exp){MessageBox.Show(exp.Message);}}//对窗体进行重新绘制，这将强制执行paint事件处理程序Invalidate();}/// <summary>/// 在控件需要重新绘制时发生/// </summary>private void Form1_Paint(object sender, PaintEventArgs e){//获取Graphics对象Graphics g = e.Graphics;if (curBitmpap != null){//使用DrawImage方法绘制图像//160,20：显示在主窗体内，图像左上角的坐标//curBitmpap.Width, curBitmpap.Height图像的宽度和高度g.DrawImage(curBitmpap, 160, 20, curBitmpap.Width, curBitmpap.Height);}}/// <summary>/// 关闭窗体 /// </summary>private void close_Click(object sender, EventArgs e){this.Close();}private void histogram_Click(object sender, EventArgs e){if (curBitmpap != null){//定义并实例化新窗体，并把图像数据传递给它histForm histoGram = new histForm(curBitmpap);histoGram.ShowDialog();}}private void linearPO_Click(object sender, EventArgs e){if (curBitmpap!=null){//实例化linearPOForm窗体linearPOForm linearForm = new linearPOForm();//点击确定按钮if (linearForm.ShowDialog()==DialogResult.OK){Rectangle rect = new Rectangle(0, 0, curBitmpap.Width, curBitmpap.Height);System.Drawing.Imaging.BitmapData bmpData = curBitmpap.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, curBitmpap.PixelFormat);IntPtr ptr = bmpData.Scan0;int bytes = curBitmpap.Width * curBitmpap.Height;byte[] grayValues = new byte[bytes];System.Runtime.InteropServices.Marshal.Copy(ptr, grayValues, 0, bytes);int temp = 0;//得到斜率double a = Convert.ToDouble(linearForm.GetScaling);//得到偏移量double b = Convert.ToDouble(linearForm.GetOffset);for (int i = 0; i < bytes; i++){//根据公式计算线性点运算//加0.5表示四舍五入temp = (int)(a * grayValues[i] + b + 0.5);//灰度值限制在0~255之间//大于255，则为255；小于0则为0if (temp>255){grayValues[i] = 255;}else if (temp<0){grayValues[i] = 0;}else{grayValues[i] = (byte)temp;}}System.Runtime.InteropServices.Marshal.Copy(grayValues, 0, ptr, bytes);curBitmpap.UnlockBits(bmpData);}Invalidate();}}}
}