c#数字图像处理（三）灰度直方图

灰度直方图是灰度的函数,描述的是图像中具有该灰度级的像素的个数。如果用直角坐标系来表示,则它的横坐标是灰度级,纵坐标是该灰度出现的概率(像素的个数)。

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 histForm : Form

    {

        //利用构造函数实现窗体之间的数据传递

        public histForm(Bitmap bmp)

        {

            InitializeComponent();

            //把主窗体的图像数据传递给从窗体

            bmpHist = bmp;

            //灰度级计数

            countPixel = new int[];  //8位可表示256个灰度级

        }

        private void close_Click(object sender, EventArgs e)

        {

            this.Close();

        }

        //图像数据

        private System.Drawing.Bitmap bmpHist;

        //灰度等级

        private int[] countPixel;

        //记录最大的灰度级个数

        private int maxPixel;

        /// <summary>

        /// 计算各个灰度级所具有的像素个数

        /// </summary>

        private void histForm_Load(object sender, EventArgs e)

        {

            //锁定8位灰度位图

            Rectangle rect = new Rectangle(, , bmpHist.Width, bmpHist.Height);

            System.Drawing.Imaging.BitmapData bmpData = bmpHist.LockBits(rect,

                System.Drawing.Imaging.ImageLockMode.ReadWrite, bmpHist.PixelFormat);

            IntPtr ptr = bmpData.Scan0;

            int bytes = bmpHist.Width * bmpHist.Height;

            byte[] grayValues = new byte[bytes];

            System.Runtime.InteropServices.Marshal.Copy(ptr, grayValues, , bytes);//灰度值数据存入grayValues中

            byte temp = ;

            maxPixel = ;

            //灰度等级数组清零

            Array.Clear(countPixel, , );

            //计算各个灰度级的像素个数

            for (int i = ; i < bytes; i++)

            {

                //灰度级

                temp = grayValues[i];

                //计数加1

                countPixel[temp]++;

                if (countPixel[temp] > maxPixel)

                {

                    //找到灰度频率最大的像素数，用于绘制直方图

                    maxPixel = countPixel[temp];

                }

            }

            //解锁

            System.Runtime.InteropServices.Marshal.Copy(grayValues, , ptr, bytes);

            bmpHist.UnlockBits(bmpData);

        }

        /// <summary>

        /// 绘制直方图

        /// </summary>

        private void histForm_Paint(object sender, PaintEventArgs e)

        {

            //获取Graphics对象

            Graphics g = e.Graphics;

            //创建一个宽度为1的黑色钢笔

            Pen curPen = new Pen(Brushes.Black, );

            //绘制坐标轴

            g.DrawLine(curPen, , , , );//横坐标

            g.DrawLine(curPen, , , , );//纵坐标

            //绘制并标识坐标刻度

            g.DrawLine(curPen, , , , );

            g.DrawLine(curPen, , , , );

            g.DrawLine(curPen, , , , );

            g.DrawLine(curPen, , , , );

            g.DrawLine(curPen, , , , );

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(, ));

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(,));

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(, ));

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(, ));

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(, ));

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(, ));

            g.DrawLine(curPen, , , , );

            g.DrawString("", new Font("New Timer", ), Brushes.Black, new PointF(, ));

            g.DrawString(maxPixel.ToString(), new Font("New Timer", ), Brushes.Black, new PointF(, ));

            //绘制直方图

            double temp = ;

            for (int i = ; i < ; i++)

            {

                //纵坐标长度

                temp = 200.0 * countPixel[i] / maxPixel;

                g.DrawLine(curPen,  + i, ,  + i,  - (int)temp);

            }

            //释放对象

            curPen.Dispose();

        }

    }

}