Can someone help me with this C#

Question

Hi, Iv had to convert a program from Java to C#, I thought I had done it, but it doesnt work, and Im at a loose end because I cant figure out why it isnt working. Anyway, what it is is a Mandelbrot Set that Im trying to display in a picturebox, I am drawing the fractal to a bitmap then getting the picturebox to display the bitmap. If anyone can explain what Im doing wrong that would be great.

 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;
using System.Drawing.Drawing2D;
using System.Design;

namespace Assignment_Attempt_3
{
    public partial class Form1 : Form
    {


        public Form1()
        {
            InitializeComponent();
            Image bp = new Bitmap(this.pictureBox1.Height,this.pictureBox1.Width);
	        Graphics g1 = Graphics.FromImage(bp);
            pictureBox1.Image = bp;

        }
            public struct HSBColor
    {
        float h;
        float s;
        float b;
        int a;

        public HSBColor(float h, float s, float b)
        {
            this.a = 0xff;
            this.h = Math.Min(Math.Max(h, 0), 255);
            this.s = Math.Min(Math.Max(s, 0), 255);
            this.b = Math.Min(Math.Max(b, 0), 255);
        }

        public HSBColor(int a, float h, float s, float b)
        {
            this.a = a;
            this.h = Math.Min(Math.Max(h, 0), 255);
            this.s = Math.Min(Math.Max(s, 0), 255);
            this.b = Math.Min(Math.Max(b, 0), 255);
        }

        public float H
        {
            get { return h; }
        }

        public float S
        {
            get { return s; }
        }

        public float B
        {
            get { return b; }
        }

        public int A
        {
            get { return a; }
        }

        public Color Color
        {
            get
            {
                return FromHSB(this);
            }
        }
        
        public static Color FromHSB(HSBColor hsbColor)
        {
            float r = hsbColor.b;
            float g = hsbColor.b;
            float b = hsbColor.b;
            if (hsbColor.s != 0)
            {
                float max = hsbColor.b;
                float dif = hsbColor.b * hsbColor.s / 255f;
                float min = hsbColor.b - dif;

                float h = hsbColor.h * 360f / 255f;

                if (h < 60f)
                {
                    r = max;
                    g = h * dif / 60f + min;
                    b = min;
                }
                else if (h < 120f)
                {
                    r = -(h - 120f) * dif / 60f + min;
                    g = max;
                    b = min;
                }
                else if (h < 180f)
                {
                    r = min;
                    g = max;
                    b = (h - 120f) * dif / 60f + min;
                }
                else if (h < 240f)
                {
                    r = min;
                    g = -(h - 240f) * dif / 60f + min;
                    b = max;
                }
                else if (h < 300f)
                {
                    r = (h - 240f) * dif / 60f + min;
                    g = min;
                    b = max;
                }
                else if (h <= 360f)
                {
                    r = max;
                    g = min;
                    b = -(h - 360f) * dif / 60 + min;
                }
                else
                {
                    r = 0;
                    g = 0;
                    b = 0;
                }
            }

            return Color.FromArgb
                (
                    hsbColor.a,
                    (int)Math.Round(Math.Min(Math.Max(r, 0), 255)),
                    (int)Math.Round(Math.Min(Math.Max(g, 0), 255)),
                    (int)Math.Round(Math.Min(Math.Max(b, 0), 255))
                    );
        }
       
    }
	private const int MAX = 256;      // max iterations
	private const double SX = -2.025; // start value real
	private const double SY = -1.125; // start value imaginary
	private const double EX = 0.6;    // end value real
	private const double EY = 1.125;  // end value imaginary
	private static int x1, y1, xs, ys, xe, ye;
	private static double xstart, ystart, xende, yende, xzoom, yzoom;
	private static bool action, rectangle, finished;
	private static float xy;
	private Image bp;
	private Graphics g1;
    //private HSB HSBcol=new HSB();

    public void init() // all instances will be prepared
    {
        //HSBcol = new HSB();
        this.Size = new Size(640, 480);
        finished = false;
        x1 = this.Width;
        y1 = this.Height;
        xy = (float)x1 / (float)y1;
       //?JAVA? picture = createImage(x1, y1);
       //?JAVA? g1 = picture.getGraphics();
        finished = true;
        mandelbrot();
    }

    public void destroy() // delete all instances 
    {
        if (finished)
        {
            bp = null;
            g1 = null;
            GC.Collect(); // garbage collection
        }
    }

    public void start()
    {
        action = false;
        rectangle = false;
        initvalues();
        xzoom = (xende - xstart) / (double)x1;
        yzoom = (yende - ystart) / (double)y1;
        mandelbrot();
    }

    public void stop()
    {
    }

    private void mandelbrot() // calculate all points
    {
        int x, y;
        float h, b, alt = 0.0f;

        action = false;
        for (x = 0; x < x1; x += 2)
            for (y = 0; y < y1; y++)
            {
                h = pointcolour(xstart + xzoom * (double)x, ystart + yzoom * (double)y); // color value
                if (h != alt)
                {
                    b = 1.0f - h * h; // brightnes

                    Color color = HSBColor.FromHSB(new HSBColor(h * 255, 0.8f * 255, b * 255));  // VERY IMPORTANT
                    //djm 
                    alt = h;
                    Pen pen = new Pen(color);
                    g1.DrawLine(pen, x, y, x + 1, y);  
                }
            }
        action = true;
    }

    private float pointcolour(double xwert, double ywert) // color value from 0.0 to 1.0 by iterations
    {
        double r = 0.0, i = 0.0, m = 0.0;
        int j = 0;

        while ((j < MAX) && (m < 4.0))
        {
            j++;
            m = r * r - i * i;
            i = 2.0 * r * i + ywert;
            r = m + xwert;
        }
        return (float)j / (float)MAX;
    }

    private void initvalues() // reset start values
    {
        xstart = SX;
        ystart = SY;
        xende = EX;
        yende = EY;
        if ((float)((xende - xstart) / (yende - ystart)) != xy)
            xstart = xende - (yende - ystart) * (double)xy;
    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        //e.consume();
        if (action)
        {
            xs = e.X;
            ys = e.Y;
        }
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        int z, w;

        //e.consume();
        if (action)
        {
            xe = e.X;
            ye = e.Y;
            if (xs > xe)
            {
                z = xs;
                xs = xe;
                xe = z;
            }
            if (ys > ye)
            {
                z = ys;
                ys = ye;
                ye = z;
            }
            w = (xe - xs);
            z = (ye - ys);
            if ((w < 2) && (z < 2)) initvalues();
            else
            {
                if (((float)w > (float)z * xy)) ye = (int)((float)ys + (float)w / xy);
                else xe = (int)((float)xs + (float)z * xy);
                xende = xstart + xzoom * (double)xe;
                yende = ystart + yzoom * (double)ye;
                xstart += xzoom * (double)xs;
                ystart += yzoom * (double)ys;
            }
            xzoom = (xende - xstart) / (double)x1;
            yzoom = (yende - ystart) / (double)y1;
            mandelbrot();
            rectangle = false;
            Refresh();
        }

    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        //e.consume();
        if (action)
        {
            xe = e.X;
            ye = e.Y;
            rectangle = true;
            Refresh();
        }
    }


    }
}