c#數字圖像處理（四）線性點運算

 

灰度圖像的點運算可分為線性點運算和非線性點運算兩種。
4.1線性點運算定義
線性點運算就是輸出灰度級與輸入灰度級呈線性關系的點運算。在這種情況下,灰度變換函數的形式為:

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

其中 f(x,y) 為輸入圖像在點 (x,y) 的灰度值, g(x,y) 為相應的輸出點的灰度值。顯然,如果P=1和L=0,g(x,y)就是f(x,y)的復制;如果P<1,輸出圖像的對比度將增大;如果P>1,則對比度將減少;如果P=1而L≠0,該操作僅使所有像素的灰度值上移或下移,其效果是使整個圖像在顯示時更暗或更亮;如果P為負值,暗區域將變亮,亮區域將變暗,該操作完成了圖像求補。

 

 

 

 

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)
        {
            //設置DialogResult屬性
            this.DialogResult = DialogResult.OK;
        }

        private void close_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        //設置兩個get訪問器
        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;
        //圖像對象
        private System.Drawing.Bitmap curBitmpap;

        /// <summary>
        /// 打開圖像文件
        /// </summary>
        private void open_Click(object sender, EventArgs e)
        {
            //創建OpenFileDialog
            OpenFileDialog opnDlg = new OpenFileDialog();
            //為圖像選擇一個篩選器
            opnDlg.Filter = "所有圖像文件|*.bmp;*.pcx;*.png;*.jpg;*.gif;" +
                "*.tif;*.ico;*.dxf;*.cgm;*.cdr;*.wmf;*.eps;*.emf|" +
                "位圖(*.bmp;*.jpg;*.png;...)|*.bmp;*.pcx;*.png;*.jpg;*.gif;*.tif;*.ico|" +
                "矢量圖(*.wmf;*.eps;*.emf;...)|*.dxf;*.cgm;*.cdr;*.wmf;*.eps;*.emf";
            //設置對話框標題
            opnDlg.Title = "打開圖像文件";
            //啟用“幫助”按鈕
            opnDlg.ShowHelp = true;

            //如果結果為“打開”，選定文件
            if (opnDlg.ShowDialog() == DialogResult.OK)
            {
                //讀取當前選中的文件名
                curFileName = opnDlg.FileName;
                //使用Image.FromFile創建圖像對象
                try
                {
                    curBitmpap = (Bitmap)Image.FromFile(curFileName);
                }
                catch (Exception exp)
                {
                    MessageBox.Show(exp.Message);
                }
            }
            //對窗體進行重新繪制，這將強制執行paint事件處理程序
            Invalidate();
        }

        /// <summary>
        /// 在控件需要重新繪制時發生
        /// </summary>
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            //獲取Graphics對象
            Graphics g = e.Graphics;
            if (curBitmpap != null)
            {
                //使用DrawImage方法繪制圖像
                //160,20：顯示在主窗體內，圖像左上角的坐標
                //curBitmpap.Width, curBitmpap.Height圖像的寬度和高度
                g.DrawImage(curBitmpap, 160, 20, curBitmpap.Width, curBitmpap.Height);
            }
        }

        /// <summary>
        /// 關閉窗體 
        /// </summary>
        private void close_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void histogram_Click(object sender, EventArgs e)
        {
            if (curBitmpap != null)
            {
                //定義並實例化新窗體，並把圖像數據傳遞給它
                histForm histoGram = new histForm(curBitmpap);
                histoGram.ShowDialog();
            }
        }

        private void linearPO_Click(object sender, EventArgs e)
        {
            if (curBitmpap!=null)
            {
                //實例化linearPOForm窗體
                linearPOForm linearForm = new linearPOForm();

                //點擊確定按鈕
                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++)
                    {
                        //根據公式計算線性點運算
                        //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之間
                        //大於255，則為255；小於0則為0
                        if (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();
            }
        }
    }
}