C# IMAPRO Binarize

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace ImageEditor
{
    public partial class BinarizeImage : Form
    {
        Bitmap image;
        public BinarizeImage(Bitmap img)
        {
            this.image = img;
            InitializeComponent();
            binaryString();
        }

        private void binaryString()
        {
            int w = image.Width;
            int h = image.Height;
            if (h > 400 || w >400)
            {
                float nh = (float)h * .75f;
                float nw = (float)w * .75f;
                Bitmap newimg = new Bitmap((int)nw, (int)nh);
                using (Graphics grx = Graphics.FromImage(newimg))
                {
                    grx.DrawImage(image,0,0,nw,nh);
                }
                image = newimg;
            }
            string texto = "";
            Bitmap map = (Bitmap)image;
            string[] arr = new string[image.Height];
            //string[] arr = new string[img.Height];
            for (int i = 0; i < image.Height; i++)
            {

                for (int j = 0; j < image.Width; j++)
                {
                    //richTextBox1.Font = new Font(Font.Name, 10, Font.Style);
                    if ((map.GetPixel(j, i).A == 255 && map.GetPixel(j, i).B == 255 && map.GetPixel(j, i).G == 255 && map.GetPixel(j, i).R == 255))
                    {
                        texto += "1";
                    }
                    else
                    {
                        texto += "0";
                    }

                }
                texto = texto + "\n";
                arr[i] = texto;

            }
            //Bitmap bmap = (Bitmap)image;
            for (int i = 0; i < arr.Length; i++)
            {
                AutoScroll = true;
                AutoScrollMinSize = new Size(image.Width * 4, image.Height * 5);
                richTextBox1.Size = new Size(image.Width * 4, image.Height * 5);
                richTextBox1.Text = arr[i];
            }
        }

    }
}