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();
        }
    }
}