Use OpenCVdotNet to Capture Object on Webcam

using System;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;
using System.Windows.Forms;
using OpenCVDotNet; //don't forget to add opencvdotnel.dll as Reference

namespace Objcap
{
    public partial class Form1 : Form
    {       
        private CVCapture capture;            //buffer for captured image from webcam
        private CVImage backgnd;              //buffer for previous image, subtract's result and captured image
        private byte threshold=30;            //threshold value = 30
        private bool only_first = false;      //flag
        private int filename = 0;

        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            timer1.Enabled = !(timer1.Enabled); //toggle start/stop 
            if (timer1.Enabled)
                capture = new CVCapture(0);     //start camera when timer enabled
            else
                capture.Release();              //stop camera when timer disabled
        }        
        private void timer1_Tick(object sender, EventArgs e)
        {
            using (CVImage frame = capture.QueryFrame())  //get camera frame
            {
                frame.Resize(160, 120);             //resize image to 160x120 pixel
                if (only_first == false)            //only first time
                {
                    backgnd = new CVImage(frame);   //copy buffer to get the same size
                    only_first = true;              //disable flag forever
                }
                //gray scale conversion
                for (int row = 0; row < frame.Height; ++row)
                {
                    for (int col = 0; col < frame.Width; ++col)
                    {
                        CVRgbPixel pixel = frame[row, col]; //get current pixel
                        byte bwValue = pixel.BwValue;   //get the gray color
                        frame[row, col] = new CVRgbPixel(bwValue, bwValue, bwValue);    //set current pixel to gray
                    }
                }
                int pixelnum = 0; // number of different pixel
                for (int row = 0; row < frame.Height; ++row)
                {
                    for (int col = 0; col < frame.Width; ++col)
                    {
                        if (Math.Abs(frame[row, col].BwValue - backgnd[row, col].BwValue) > threshold)
                        {                       
                            pixelnum++;
                        }
                        backgnd[row, col] = frame[row, col];  // save current frame to backgroun frame for next time
                    }
                } 
                 pictureBox1.Image = frame.ToBitmap();  //display image
                 int objsize = 500;  //depend on Size of Object to be captured
                                     // if number of different pixel > objsize then save image to hard drive                 
                if (pixelnum > objsize)
                {
                    using (CVImage frame2 = capture.QueryFrame())
                    {                              
                        // Capture color image
                        filename++;                                                               //change file name   
                        string path = "D:/webcam/";                                               // Path to save file
                        path += DateTime.Today.Day.ToString()+"."+filename.ToString() + ".jpg";   // Full path - file name with added day saved                       
                        frame2.ToBitmap().Save(path, ImageFormat.Jpeg);                           // Save image file with max resolution of webcam
                        frame2.Resize(160, 120);                                                  // Resize image to show on picturebox3
                        pictureBox3.Image = frame2.ToBitmap();                                    //Show captured image
                    }
                }      
                 label5.Text = "Pictures: " + filename.ToString();                                // Show number of captured imagea  
            }
            GC.Collect();
        }
    }
}