Convert BMP to Hex C# code

using System;
using System.Drawing;
using System.IO;
using System.Windows.Forms;



namespace _128x64oled_icon
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        string filePath, SavedFile;
        string SavedFolder = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
        Bitmap myBitmap;

        private void bt_convert_Click(object sender, EventArgs e)
        {
            if (!File.Exists(filePath))
            {
                MessageBox.Show("No existing file selected");
                return;
            }
 
            int userWidth = int.Parse(textWidth.Text);
            int userHeight = int.Parse(textHeight.Text);
           

            SavedFolder =  Path.GetDirectoryName(filePath);  // save folder for later
            SavedFile = Path.GetFileName(filePath);  // save   file

            for (int y = 0; y < userHeight; y++)   // y < 64
            {
                for (int x = 0; x < userWidth;  x++)  // x <128
                {
                    Color pixelColor =  myBitmap.GetPixel(x, y);
                    if (pixelColor.R < 170)   //  || (pixelColor.B < 93) || (pixelColor.G < 93))      // was 170
                    {
                      myBitmap.SetPixel(x, y, Color.Black);
                    }
                    else
                    {
                        myBitmap.SetPixel(x, y, Color.White);
                    }
                }
            }
            //    MessageBox.Show(pixelColor.R.ToString()  + " " + pixelColor.G.ToString() + " " + pixelColor.B.ToString());

            myBitmap.Save(filePath + "_black.bmp");


            // new code
            int byteSize = userWidth * (userHeight / 8);
            byte[] normal_hex = new byte[byteSize]; 

            int k = -1;
            


            Array.Clear(normal_hex, 0, normal_hex.Length);

            //  start code for Arduino Adafruit_GFX  bytes from left to right
            if (Ada_rb.Checked == true)
            {
                int mask = 0;

                Array.Clear(normal_hex, 0, normal_hex.Length);
                for (int y = 0; y < userHeight; y++)
                {
                    for (int x = 0; x < userWidth; x++)
                    {
                        if ((x % 8) == 0)
                        {
                            k++;
                            mask = 8;
                        }

                        mask--;

                        Color pixelColor = myBitmap.GetPixel(x, y);   //  x= 0 -> 64 = 8 bytes y = 0-> 64 = 8 bytes
                        if (pixelColor.R == 0)
                        {
                            normal_hex[k] += (byte)(1 << mask);
                        }
                    }
                }
            }   // end code Adafruit
            else
            {  


                //  code for ATtiny85  SSD1306_minimal  bytes from top to bottom  
                for (int y = 0; y < userHeight; y += 8)
                {
                    for (int x = 0; x < userWidth; x++)
                    {
                        k++;

                        for (int i = 0; i < 8; i++)
                        {

                            Color pixelColor = myBitmap.GetPixel(x, i + y);   //  x= 0 -> 64 = 8 bytes y = 0-> 64 = 8 bytes
                            if (pixelColor.R == 0)
                            {
                                normal_hex[k] += (byte)(1 << i);
                            }
                        }
                    }
                }
            }  // end code mini

            FileStream fl =  File.Create(SavedFolder + "\\" +    SavedFile + ".hex");
            string hex = BitConverter.ToString(normal_hex).Replace("-", ",0x");

            string Plain = Path.GetFileNameWithoutExtension(SavedFile);

            StreamWriter s = new StreamWriter(fl);
            s.Write("// ");
            s.Write(userWidth);
            s.Write(" x ");
            s.WriteLine(userHeight);
            s.Write("const unsigned char ");
            s.Write(Plain);
            s.WriteLine(" [] PROGMEM = { ");
            s.Write("0x");
            s.Write(hex);
            s.WriteLine("};");
            s.Close();



            tb_message.Text =   SavedFolder + "\\" + SavedFile  + ".hex created!";
            //  MessageBox.Show(filePath  +".bin created!");


            //   Application.Exit();
        }

        private void mini_rb_CheckedChanged(object sender, EventArgs e)
        {
            tb_message.Text = "mini = " + mini_rb.Checked + "   Ada = " + Ada_rb.Checked;

        }


        private void bt_browse_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog   openFileDialog1 = new OpenFileDialog())
            {

                openFileDialog1.InitialDirectory =   SavedFolder;


                openFileDialog1.Filter = "bmp (*.bmp)|*.bmp|All files (*.*)|*.*";

                openFileDialog1.FilterIndex = 1;


                openFileDialog1.Multiselect = false;
                openFileDialog1.Title =  "Please, Select Source File";
                openFileDialog1.FileName= "";

                if   (openFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    filePath = openFileDialog1.FileName;
                    myBitmap = new Bitmap(filePath); // Get the color of a pixel  within myBitmap.
                    textWidth.Text = myBitmap.Width.ToString();
                    textHeight.Text = myBitmap.Height.ToString();
                }
            }
   
        }  // private
    }
}