[摘录] 一种改进的边界检测的方法

Each pixel has 8 neighbours. If pixel co-ordinate is x & y. Then its neighbouring pixels are (x+1,y+1), (x,y+1), (x+1,y), (x-1,y-1), (x,y-1), (x-1,y), (x-1,y+1) & (x+1,y-1). The color difference of two pixels means RGB difference among the two pixels. If two pixels are (x,y) & (a,b), then the color difference will be:

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int total = Math.Abs(b.GetPixel(a, b).B - b.GetPixel(x, y).B) + 
		Math.Abs(b.GetPixel(a, b).R - b.GetPixel(x, y).R) + 
		Math.Abs(b.GetPixel(a, b).G - b.GetPixel(x, y).G);

In my method of edge detection, 1st takes a bitmap whose height & width is similar to the original image and the color of all its pixels is white.

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int n, m;
n = b.Height;
m = b.Width;
int total = 0;
Bitmap B1 = new Bitmap(m, n);
for (int i = 0; i < m; i++)
    for (int j = 0; j < n; j++)
    {
        B1.SetPixel(i, j, Color.White);
    }

Then for each pixel of an image, it determines the color difference, of its neighbour's pixels. If any neighbour's color difference is greater or equal than the threshold value, then it is an edge & gives the pixel value Black. Normally threshold value is 90. But if we are increasing the threshold value, then the edge will decrease and if the threshold value decreases then the edge will increase.

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for (int i = 1; i < m - 1; i++)
for (int j = 1; j < n - 1; j++)
{
    total = Math.Abs(b.GetPixel(i + 1, j + 1).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i + 1, j + 1).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i + 1, j + 1).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i, j + 1).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i, j + 1).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i, j + 1).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i + 1, j).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i + 1, j).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i + 1, j).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i - 1, j - 1).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i - 1, j - 1).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i - 1, j - 1).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i, j - 1).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i, j - 1).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i, j - 1).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i - 1, j).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i - 1, j).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i - 1, j).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i - 1, j + 1).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i - 1, j + 1).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i - 1, j + 1).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
    
    total = Math.Abs(b.GetPixel(i + 1, j - 1).B - b.GetPixel(i, j).B) + 
    	Math.Abs(b.GetPixel(i + 1, j - 1).R - b.GetPixel(i, j).R) + 
    	Math.Abs(b.GetPixel(i + 1, j - 1).G - b.GetPixel(i, j).G);
    if (total > _proposedThresoldValue)
    { B1.SetPixel(i, j, Color.Black); continue; }
}

We can compare my method of edge detection to sobel or prewitt edge detection. For comparing this, we have to select sobel or prewitt check box and proposed check box. Black pixel indicates that this pixel is common for proposed and sobel/prewitt. Red pixel indicates that this pixel is only for sobel/prewitt. And blue pixel indicates that this pixel is only for proposed.

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if (checkBox_sobel.Checked && checkBox_pro.Checked)
{
    Bitmap b1 = (Bitmap)pictureBox2.Image;
    Bitmap b2 = (Bitmap)pictureBox4.Image;
    Bitmap map = new Bitmap(pictureBox2.Image.Width, pictureBox2.Image.Height);
    
    for (int i = 1; i < b1.Width - 1; i++)
        for (int j = 1; j < b1.Height - 1; j++)
        {
            if (b1.GetPixel(i, j).R == 0 && b2.GetPixel(i, j).R == 0)
                map.SetPixel(i, j, Color.Black);
            else if (b1.GetPixel(i, j).R == 0)
                map.SetPixel(i, j, Color.Red);
            else if (b2.GetPixel(i, j).R == 0)
                map.SetPixel(i, j, Color.Blue);
        }
        
    pictureBox5.Image = map;
}
else if (checkBox_prewitt.Checked && checkBox_pro.Checked)
{
    Bitmap b1 = (Bitmap)pictureBox3.Image;
    Bitmap b2 = (Bitmap)pictureBox4.Image;
    Bitmap map = new Bitmap(pictureBox3.Image.Width, pictureBox3.Image.Height);
    
    for (int i = 1; i < b1.Width - 1; i++)
        for (int j = 1; j < b1.Height - 1; j++)
        {
            if (b1.GetPixel(i, j).R == 0 && b2.GetPixel(i, j).R == 0)
                map.SetPixel(i, j, Color.Black);
            else if (b1.GetPixel(i, j).R == 0)
                map.SetPixel(i, j, Color.Red);
            else if (b2.GetPixel(i, j).R == 0)
                map.SetPixel(i, j, Color.Blue);
        }
        
    pictureBox5.Image = map;
}

If we decrease the threshold value, than edge will be thicker and if we increase the threshold value, then edge will be wider.

源码:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace edge_detect
{
    public partial class Form1 : Form
    {
        private string _fileName = "";
        private int _proposedThresoldValue = 90;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            openFileDialog1.ShowDialog();
        }

        private void openFileDialog1_FileOk(object sender, CancelEventArgs e)
        {

            _fileName = openFileDialog1.FileName;
            pictureBox1.Image = Image.FromFile(_fileName);
        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            pictureBox2.Image = sobel(pictureBox1.Image);
        }

        public Image sobel(Image im)
        {
            int[,] gx = new int[,] { { -1, 0, 1 }, { -2, 0, 2 }, { -1, 0, 1 } };   //  The matrix Gx
            int[,] gy = new int[,] { { 1, 2, 1 }, { 0, 0, 0 }, { -1, -2, -1 } };  //  The matrix Gy
            Bitmap b = (Bitmap)im;
            Bitmap b1 = new Bitmap(im);
            for (int i = 1; i < b.Height - 1; i++)   // loop for the image pixels height
            {
                for (int j = 1; j < b.Width - 1; j++) // loop for image pixels width    
                {
                    float new_x = 0, new_y = 0;
                    float c;
                    for (int hw = -1; hw < 2; hw++)  //loop for cov matrix
                    {
                        for (int wi = -1; wi < 2; wi++)
                        {
                            c = (b.GetPixel(j + wi, i + hw).B + b.GetPixel(j + wi, i + hw).R + b.GetPixel(j + wi, i + hw).G) / 3;
                            new_x += gx[hw + 1, wi + 1] * c;
                            new_y += gy[hw + 1, wi + 1] * c;
                        }
                    }


                    if (new_x * new_x + new_y * new_y > 128 * 128)
                        b1.SetPixel(j, i, Color.Black);
                    else
                        b1.SetPixel(j, i, Color.White);
                }
            }
            return (Image)b1;
        }


        private void button5_Click(object sender, EventArgs e)
        {
            Prewitt p = new Prewitt();
            Image edgedImage;
            edgedImage = p.apply(pictureBox1.Image);
            pictureBox3.Image = edgedImage;
        }

        private void button_save_Click(object sender, EventArgs e)
        {
            saveFileDialog1.ShowDialog();
        }

        private void saveFileDialog1_FileOk(object sender, CancelEventArgs e)
        {
            /*
            save_file = saveFileDialog1.FileName;
            Bitmap b = new Bitmap(pictureBox1.Image);
            b.Save(save_file);
            */
        }


        private void button8_Click(object sender, EventArgs e)
        {
            pictureBox4.Image = ProposedEdgeDetection((Bitmap)pictureBox1.Image);
        }

        private Bitmap ProposedEdgeDetection(Bitmap b)
        {
            int n, m;
            n = b.Height;
            m = b.Width;
            int total = 0;
            Bitmap B1 = new Bitmap(m, n);

            for (int i = 0; i < m; i++)
                for (int j = 0; j < n; j++)
                {
                    B1.SetPixel(i, j, Color.White);
                }

            for (int i = 1; i < m - 1; i++)
                for (int j = 1; j < n - 1; j++)
                {


                    total = Math.Abs(b.GetPixel(i + 1, j + 1).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i + 1, j + 1).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i + 1, j + 1).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                    total = Math.Abs(b.GetPixel(i, j + 1).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i, j + 1).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i, j + 1).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                    total = Math.Abs(b.GetPixel(i + 1, j).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i + 1, j).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i + 1, j).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                    total = Math.Abs(b.GetPixel(i - 1, j - 1).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i - 1, j - 1).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i - 1, j - 1).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }


                    total = Math.Abs(b.GetPixel(i, j - 1).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i, j - 1).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i, j - 1).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                    total = Math.Abs(b.GetPixel(i - 1, j).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i - 1, j).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i - 1, j).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                    total = Math.Abs(b.GetPixel(i - 1, j + 1).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i - 1, j + 1).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i - 1, j + 1).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                    total = Math.Abs(b.GetPixel(i + 1, j - 1).B - b.GetPixel(i, j).B) + Math.Abs(b.GetPixel(i + 1, j - 1).R - b.GetPixel(i, j).R) + Math.Abs(b.GetPixel(i + 1, j - 1).G - b.GetPixel(i, j).G);
                    if (total > _proposedThresoldValue)
                    { B1.SetPixel(i, j, Color.Black); continue; }

                }

            return B1;
        }

        private void button9_Click(object sender, EventArgs e)
        {
            Bitmap b = (Bitmap)black_white(pictureBox1.Image);
            pictureBox1.Image = (Image)b;
        }

        public Bitmap black_white(Image Im)
        {
            Bitmap b = (Bitmap)Im;
            int A, B, C, c;
            for (int i = 1; i < b.Height; i++)   // loop for the image pixels height
            {
                for (int j = 1; j < b.Width; j++)  // loop for the image pixels width
                {
                    Color col;
                    col = b.GetPixel(j, i);

                    A = Convert.ToInt32(col.R);
                    B = Convert.ToInt32(col.G);
                    C = Convert.ToInt32(col.B);
                    ////if(A>128||B>128||C>128)
                    if ((A > 128 && B > 128) || (A > 128 && C > 128) || (C > 128 && B > 128))
                        c = 255;
                    else
                        c = 0;

                    if (c == 0)
                        b.SetPixel(j, i, Color.Black);
                    else
                        b.SetPixel(j, i, Color.GhostWhite);

                }
            }
            return b;
        }

        private void button11_Click_1(object sender, EventArgs e)
        {
            Bitmap b = new Bitmap(pictureBox2.Image);

            pictureBox1.Image = (Image)b;
            pictureBox2.Image = (Image)black_white(pictureBox2.Image);
        }

        private void button16_Click(object sender, EventArgs e)
        {
            Bitmap b = new Bitmap(gray(pictureBox1.Image));
            pictureBox1.Image = (Image)b;
        }

        public Bitmap gray(Image Im)
        {
            Bitmap b = (Bitmap)Im;
            for (int i = 1; i < b.Height; i++)   // loop for the image pixels height
            {
                for (int j = 1; j < b.Width; j++)  // loop for the image pixels width
                {
                    Color col;
                    col = b.GetPixel(j, i);
                    b.SetPixel(j, i, Color.FromArgb((col.R + col.G + col.B) / 3, (col.R + col.G + col.B) / 3, (col.R + col.G + col.B) / 3));

                }
            }
            return b;
        }

        private void button21_Click(object sender, EventArgs e)
        {
            Bitmap b = new Bitmap(pictureBox4.Image);
            pictureBox1.Image = (Image)b;
        }

        private void button22_Click(object sender, EventArgs e)
        {
            Bitmap b = new Bitmap(pictureBox3.Image);
            pictureBox1.Image = (Image)b;
        }

        private void button3_Click(object sender, EventArgs e)
        {
            _proposedThresoldValue = Convert.ToInt16(textBox1.Text);
        }

        private void button_cmp_Click(object sender, EventArgs e)
        {
            if (checkBox_sobel.Checked && checkBox_pro.Checked)
            {
                Bitmap b1 = (Bitmap)pictureBox2.Image;
                Bitmap b2 = (Bitmap)pictureBox4.Image;
                Bitmap map = new Bitmap(pictureBox2.Image.Width, pictureBox2.Image.Height);

                for (int i = 1; i < b1.Width - 1; i++)
                    for (int j = 1; j < b1.Height - 1; j++)
                    {
                        if (b1.GetPixel(i, j).R == 0 && b2.GetPixel(i, j).R == 0)
                            map.SetPixel(i, j, Color.Black);
                        else if (b1.GetPixel(i, j).R == 0)
                            map.SetPixel(i, j, Color.Red);
                        else if (b2.GetPixel(i, j).R == 0)
                            map.SetPixel(i, j, Color.Blue);
                    }

                pictureBox5.Image = map;
            }
            else if (checkBox_prewitt.Checked && checkBox_pro.Checked)
            {
                Bitmap b1 = (Bitmap)pictureBox3.Image;
                Bitmap b2 = (Bitmap)pictureBox4.Image;
                Bitmap map = new Bitmap(pictureBox3.Image.Width, pictureBox3.Image.Height);

                for (int i = 1; i < b1.Width - 1; i++)
                    for (int j = 1; j < b1.Height - 1; j++)
                    {
                        if (b1.GetPixel(i, j).R == 0 && b2.GetPixel(i, j).R == 0)
                            map.SetPixel(i, j, Color.Black);
                        else if (b1.GetPixel(i, j).R == 0)
                            map.SetPixel(i, j, Color.Red);
                        else if (b2.GetPixel(i, j).R == 0)
                            map.SetPixel(i, j, Color.Blue);
                    }

                pictureBox5.Image = map;
            }
        }
    }
}
class Prewitt
{
    Bitmap b;
    public Image apply(Image im)
    {
        //int[,] gx = new int[,] { { -1, 0, 1 }, { -2, 0, 2 }, { -1, 0, 1 } };   //  The matrix Gx
        //int[,] gy = new int[,] { { 1, 2, 1 }, { 0, 0, 0 }, { -1, -2, -1 } };  //  The matrix Gy

        int[,] gx = new int[,] { { 1, 1, 1 }, { 0, 0, 0 }, { -1, -1, -1 } };   //  The matrix Gx
        int[,] gy = new int[,] { { -1, 0, 1 }, { -1, 0, 1 }, { -1, 0, 1 } };  //  The matrix Gy
        b = (Bitmap)im;
        Bitmap b1 = new Bitmap(b.Width, b.Height);
        for (int i = 1; i < b.Height - 1; i++)   // loop for the image pixels height
        {
            for (int j = 1; j < b.Width - 1; j++) // loop for image pixels width    
            {
                float new_x = 0, new_y = 0;
                float c;
                for (int hw = -1; hw < 2; hw++)  //loop for cov matrix
                {
                    for (int wi = -1; wi < 2; wi++)
                    {
                        c = (b.GetPixel(j + wi, i + hw).B + b.GetPixel(j + wi, i + hw).R + b.GetPixel(j + wi, i + hw).G) / 3;

                        new_x += gx[hw + 1, wi + 1] * c;
                        new_y += gy[hw + 1, wi + 1] * c;
                    }
                }
                if (new_x * new_x + new_y * new_y > 128 * 100)
                    b1.SetPixel(j, i, Color.Black);
                else
                    b1.SetPixel(j, i, Color.White);
            }
        }
        return (Image)b1;
    }
}