How do I detect objects from an image that taken from camera's live preview

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C#

.NET

object-detection

i am a fresher working on project that captures image and display on the picture box in C# .net-framework.
i have made new project for just testing code for object detection in image.
suppose i have 4 diamonds on an image. after capturing image there will be a 4 rectangles on 4 diamonds.
so i have used Emgu.Cv and code that detects object but only some objects. or not proper detection.

here is some outputs.

https://ibb.co/Hzv4SXB
https://ibb.co/ryGjjjS
https://ibb.co/3sQY9mB

here in some images the app detects the perfect objects and in some images that the app create border on image. i want to detect all the objets are there.

What I have tried:

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;
using Emgu.CV;
using Emgu.CV.Structure;
using Emgu.CV.Util;



namespace objectdetection
{
  
    public partial class Form1 : Form
    {
        Image<Bgr, byte> imgInput;
        public Bitmap img;
        bool show = false;

        public Form1()
        {
            InitializeComponent();
        }
        
        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();

            if (ofd.ShowDialog() == DialogResult.OK)
            {
               // imgInput = new Emgu.CV.Image<Emgu.CV.Structure.Bgr,Int32>((Bitmap)img);
                imgInput = new Image<Bgr, byte>(ofd.FileName);
                pictureBox1.Image = imgInput.Bitmap;
                
            }
            
        }   

        private void button2_Click(object sender, EventArgs e)
        {

            Image<Gray, byte> imgout = new Image<Gray, byte>(imgInput.Width, imgInput.Height, new Gray(10));
            Image<Gray, byte> imgout2 = new Image<Gray, byte>(imgInput.Width, imgInput.Height, new Gray(10));

            CvInvoke.CvtColor(imgInput, imgout, Emgu.CV.CvEnum.ColorConversion.Bgr2Rgb);
            pictureBox2.Image = imgout[0].Bitmap;

            CvInvoke.Threshold(imgout[0], imgout2, 1, 255, Emgu.CV.CvEnum.ThresholdType.Binary);

            VectorOfVectorOfPoint contours = new VectorOfVectorOfPoint();
            Mat hier = new Mat();

            pictureBox3.Image = imgout2.Bitmap;


            CvInvoke.FindContours(imgout[0], contours, hier, Emgu.CV.CvEnum.RetrType.External, Emgu.CV.CvEnum.ChainApproxMethod.ChainApproxSimple);

           
            Dictionary<int, double> dict = new Dictionary<int, double>();

            if (contours.Size > 0)
            {
                for (int i = 0; i < contours.Size; i++)
                {
                    double area = CvInvoke.ContourArea(contours[i]);
                    Rectangle rect = CvInvoke.BoundingRectangle(contours[i]);

                      if (rect.Width > 10 && rect.Height > 10 && area > 500)
                      {
                            dict.Add(i, area);
                      }
                }
            }



            var item = dict.OrderByDescending(v => v.Value);

           // Image<Bgr, byte> imgout1 = new Image<Bgr, byte>(imgInput.Width, imgInput.Height, new Bgr(0, 0, 0));

            foreach (var it in item)
            {
                int key = int.Parse(it.Key.ToString());
                Rectangle rect = CvInvoke.BoundingRectangle(contours[key]);
               // CvInvoke.DrawContours(imgInput, contours, key, new MCvScalar(255, 255, 255),4);
                CvInvoke.Rectangle(imgInput, rect, new MCvScalar(0, 0, 255), 5);
            }

            pictureBox4.Image = imgInput.Bitmap;

        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {

        }
    }
}