I am trying to write a code for contrast but contrast depends on threshold value.What I mean is using entered threshold value or if it is not entered by user I want to write a default value for threshold.As far as I know I should do this by using constructor but I am not good at object oriented programming.How can I do that?

Here is the code for Form1.cs:

using AForge.Video.DirectShow;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace imageprocessing
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public FilterInfoCollection devices;
        public VideoCaptureDevice camera;

        
        private void Form1_Load(object sender, EventArgs e)
        {
            devices = new FilterInfoCollection(FilterCategory.VideoInputDevice);
            foreach (FilterInfo item in devices)
            {
                cb_show.Items.Add(item.Name);

            }

            camera = new VideoCaptureDevice();
            cb_show.SelectedIndexChanged  = cb_show_SelectedIndexChanged;
        }
        private void cb_show_SelectedIndexChanged(object sender, EventArgs e)
        {
            try
            {
                if (camera.IsRunning == false)
                {
                    camera = new VideoCaptureDevice(devices[cb_show.SelectedIndex].MonikerString);
                    camera.NewFrame  = Camera_NewFrame;
                    camera.Start();
                }
            }
            catch (Exception exc)
            {
                MessageBox.Show(exc.Message   "");
            }
        }
        List<byte> alldata = new List<byte>();
        public void Camera_NewFrame(object sender, AForge.Video.NewFrameEventArgs eventArgs)
        {
            Bitmap image = (Bitmap)eventArgs.Frame.Clone();
            byte[] maindata = new byte[image.Width * 3];

            if (btn_grayWasClicked == true)
            {
                alldata.Clear();
                for (int i = 0; i < image.Height; i  )
                {
                    int count = 0;
                    for (int j = 0; j < image.Width; j  )
                    {
                        Color color = image.GetPixel(j, i);
                        maindata[count] = color.R;
                        maindata[count   1] = color.G;
                        maindata[count   2] = color.B;
                        count  = 3;
                    }
                    byte[] processGray = Gray.GrayFilter(maindata, image.Width);
                    alldata.AddRange(processGray);
                }
            }
            if (btn_thresholdWasClicked == true)
            {
                alldata.Clear();
int thresh= Convert.ToInt32(tb_contrast.Text);
            Threshold.ApplyThreshold(alldata.ToArray(),1920,thresh);
                for (int i = 0; i < image.Height; i  )
                {
                    int count = 0;
                    for (int j = 0; j < image.Width; j  )
                    {
                        Color color = image.GetPixel(j, i);
                        maindata[count] = color.R;
                        maindata[count   1] = color.G;
                        maindata[count   2] = color.B;
                        count  = 3;
                    }
                    byte[] processthreshold = Threshold.ApplyThreshold(maindata, image.Width,thresh);
                    alldata.AddRange(processthreshold);
                }
            }
        }
        private bool btn_grayWasClicked = false;
        private bool btn_thresholdWasClicked = false;

        private void btn_gray_Click(object sender, EventArgs e)
        {
            btn_grayWasClicked = true;
        }

        private void btn_threshold_Click(object sender, EventArgs e)
        {
            btn_thresholdWasClicked = true;
        }
        private void btn_contrast_Click(object sender, EventArgs e)
        {
            int kontrast = Convert.ToInt32(tb_contrast.Text);
            Contrast.contrast(alldata.ToArray(),1920,kontrast);

        }

        private void button2_Click(object sender, EventArgs e)
        {
            
            unsafe
            {
                byte[] a = new byte[691200];
                a = alldata.ToArray();

                Bitmap image = new Bitmap(1920, 360);
                Rectangle rect = new Rectangle(0, 0, 640, 360);
                BitmapData bmpData = image.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

                IntPtr ptr = bmpData.Scan0; 
                byte* ptr0 = (byte*)ptr.ToPointer();
                for (int i = 0; i < 360; i = i   3)
                {
                    for (int j = 0; j < 1920; j  )
                    {
                        a[i]=ptr0[i];
                    }

                }
                Marshal.Copy(a, 0, ptr, 691200);
                image.UnlockBits(bmpData);

                picfilter.Image = image;
            }
        }
    }
}

Here is the code for Threshold.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace imageprocessing
{
    class Threshold
    {
        public static byte[] ApplyThreshold(byte[] data, int width,int thresh)
        {
            List<byte> threshold = new List<byte>();
            byte[] all = data.ToArray();
            
            for (int j = 0; j < width-1; j  )
            {
                if (all[j] > thresh)
                {
                    threshold.Add(all[j]);
                }
                else
                    threshold.Add(all[j]);
            }
            return data;
        }
    }
}

CodePudding user response：

Instead of using:

int thresh= Convert.ToInt32(tb_contrast.Text);

You should use the int.TryParse()

for example:

int thresh;

// this is a better method to check if the textbox contains a valid integer.
if(!int.TryParse(tb_contrast.Text, out thresh))
    thresh = 20; // enter here your default value.

// you should also check the range of the value, never trust user input
// in this case you are only comparing, Always good to be critical on it
if (thresh > 255)
    thresh = 255;
else if (thresh < 0)
    thresh = 0;

To answer the title in your question.

"How can I get default value for threshold with constructor in C#?"

Your threshold class doesn't have a constructor. There is just one static method. So it's more like a helper class.