Adding red, green, and blue pixels into a list after being red form the input file

using System;
using System.IO;
using System.Collections.Generic;

namespace Module_12
{
    
    public class Program
    {
        static void Main(string[] args)
        {
            // Open the input and output file.
            FileStream inputFile = new("ScrambledFlag.ppm", FileMode.Open, FileAccess.Read);
            StreamReader reader = new(inputFile);
            FileStream outputFile = new("UnscrambledFlag.ppm", FileMode.Create, FileAccess.Write);
            StreamWriter writer = new(outputFile);

            //read header of input file
            while (!reader.EndOfStream)
            {
                
                string? nextLine = reader.ReadLine();

                if ( nextLine != null )
                {
                    string[] nextItem = nextLine.Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
                    if (nextItem.Length == 0) { continue; }

                    //reading header and converting to int
                    string? p = reader.ReadLine();
                    int x = Convert.ToInt32(nextItem[0]);
                    int y = Convert.ToInt32(nextItem[1]);
                    int z = Convert.ToInt32(reader.ReadLine());

                    List<Pixel> pixels = new List<Pixel>(x * y);

                    for (int i = 0; i < pixels.Count; i++)
                    {
                        int first;
                        int second;
                        int third;


                        pixels.Add();
                    }



                    //writing header to output file
                    //write header to output file
                    writer.WriteLine(p);
                }
            }
            
        }
    }
}