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On a canvas, how do I let the user to only draw a circle in a specified line?

Im doing school project. My task is to write a small Winform application that represents the Bezier Curve, but with some constraints.
I did almost everything, just one more step is ahead of me.
The whole program starts with an empty canvas, then the user can click on it, and a circle is drawn. After every 4th click, the bezier curve appears to that polygon. Now comes my problem.
What I am stuck with is that I have to controll somehow where the 5th click is going to be. It must be on a line that comes from 2 points: the 3rd and 4th points.
Can anybody help me with this? I have really no idea how to even start.
So far, this is my code.
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;
namespace grafika_beadando_kettesert
{
public partial class MainForm : Form
{
Graphics g;
int counter = 0;
Pen PenBlack = Pens.Black; //ezzel a tollal rajzolom a vonalat
Pen PenCurve = new Pen(Color.Blue, 3f); //ezzel a tollal rajzolom a görbét
Brush PenPoint; //Ezzel töltöm ki a pontot
int size = 4; // a lerakott pont mérete
int found = -1;
List<PointF> Points = new List<PointF>(); //ebbe a listába tárolom a pontokat
PointF p0, p1;
public MainForm()
{
InitializeComponent();
PenPoint = new SolidBrush(canvas.BackColor);
this.DoubleBuffered = true;
}
private void canvas_Paint(object sender, PaintEventArgs e)
{
g = e.Graphics;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
for (int i = 0; i < Points.Count - 1; i++) // mindig meg kell rajzolni az eddig meghúzott vonalakat a polygonból újra
g.DrawLine(PenBlack, Points[i], Points[i + 1]);
if (counter == 4)
{
DrawBeziergorbe();
counter = 0;
}
for (int i = 0; i < Points.Count; i++) // ezzel rajzolom meg az eddig felrakott pontokat újra
{
g.FillEllipse(PenPoint, Points[i].X - size, Points[i].Y - size, 2 * size, 2 * size);
g.DrawEllipse(PenBlack, Points[i].X - size, Points[i].Y - size, 2 * size, 2 * size);
}
}
private void canvas_MouseUp(object sender, MouseEventArgs e)
{
found = -1;
}
private void canvas_MouseMove(object sender, MouseEventArgs e)
{
if (found != -1)
{
Points[found] = e.Location;
canvas.Invalidate();
}
}
private void canvas_MouseDown(object sender, MouseEventArgs e)
{
for (int i = 0; i < Points.Count; i++)
{
if (Math.Abs(Points[i].X - e.X) <= size && Math.Abs(Points[i].Y - e.Y) <= size)
{
found = i;
break;
}
}
if (found == -1)
{
Points.Add(e.Location); //ha nincs túl közel a lerakott pont egy jelenlegihez, akkor hozzáadja a
//"Points" listához, hogy innen kiolvasva újra belehessen rajzolni
found = Points.Count - 1;
counter++;
canvas.Invalidate();
}
}
private void DrawBeziergorbe() //Mivel n-ed fokú bezier görbe kell, ezért használom a binomiálisos megoldást
{
int n = Points.Count - 1;
double t = 0;
double h = 1.0 / 500.0;
double b = 0.0;
p0 = new PointF(0, 0);
for (int i = 0; i <= n; i++)
{
b = B(n, i, t);
p0.X += (float)(b * Points[i].X);
p0.Y += (float)(b * Points[i].Y);
}
while (t < 1)
{
t += h;
p1 = new PointF(0, 0);
for (int i = 0; i <= n; i++)
{
b = B(n, i, t);
p1.X += (float)(b * Points[i].X);
p1.Y += (float)(b * Points[i].Y);
}
g.DrawLine(PenCurve, p0, p1);
p0 = p1;
}
}
private double B(int n, int i, double t)
{
return Binom(n, i) * (Math.Pow(1 - t, n - i) * Math.Pow(t, i));
}
private uint Binom(int n, int k)
{
if (n == 0) return 0;
else if (k == 0 || k == n) return 1;
else return Binom(n - 1, k - 1) + Binom(n - 1, k);
}
}
}

You can simply project the click position on the desired line.
If c is the click position and A and B are the two last control points, then the projected position p is:
d = B - A
p = A + dot(c - A, d) / dot(d, d) * d

Free-form selection crop C#

How can I make a free-form selection (like in paint or photoshop) in a picture box and then crop that selection and save it to a folder?
I already did a rectangle crop but I want that free-form selection..
Here is my rectangle crop:
Image img;
bool mouseClicked;
Point startPoint = new Point();
Point endPoint = new Point();
Rectangle rectCropArea;
private void Button1_Click(System.Object sender, System.EventArgs e)
{
}
private void OnLoad(System.Object sender, System.EventArgs e)
{
loadPrimaryImage();
}
private void loadPrimaryImage()
{
img = Image.FromFile("..\\..\\images.jpg");
PictureBox1.Image = img;
}
private void PicBox_MouseUp(System.Object sender, System.Windows.Forms.MouseEventArgs e)
{
mouseClicked = false;
if ((endPoint.X != -1)) {
Point currentPoint = new Point(e.X, e.Y);
Y1.Text = e.X.ToString();
Y2.Text = e.Y.ToString();
}
endPoint.X = -1;
endPoint.Y = -1;
startPoint.X = -1;
startPoint.Y = -1;
}
private void PicBox_MouseDown(System.Object sender, System.Windows.Forms.MouseEventArgs e)
{
mouseClicked = true;
startPoint.X = e.X;
startPoint.Y = e.Y;
//Display coordinates
X1.Text = startPoint.X.ToString();
Y1.Text = startPoint.Y.ToString();
endPoint.X = -1;
endPoint.Y = -1;
rectCropArea = new Rectangle(new Point(e.X, e.Y), new Size());
}
private void PicBox_MouseMove(System.Object sender, System.Windows.Forms.MouseEventArgs e)
{
Point ptCurrent = new Point(e.X, e.Y);
if ((mouseClicked)) {
if ((endPoint.X != -1)) {
//Display Coordinates
X1.Text = startPoint.X.ToString();
Y1.Text = startPoint.Y.ToString();
X2.Text = e.X.ToString();
Y2.Text = e.Y.ToString();
}
endPoint = ptCurrent;
if ((e.X > startPoint.X & e.Y > startPoint.Y)) {
rectCropArea.Width = e.X - startPoint.X;
rectCropArea.Height = e.Y - startPoint.Y;
} else if ((e.X < startPoint.X & e.Y > startPoint.Y)) {
rectCropArea.Width = startPoint.X - e.X;
rectCropArea.Height = e.Y - startPoint.Y;
rectCropArea.X = e.X;
rectCropArea.Y = startPoint.Y;
} else if ((e.X > startPoint.X & e.Y < startPoint.Y)) {
rectCropArea.Width = e.X - startPoint.X;
rectCropArea.Height = startPoint.Y - e.Y;
rectCropArea.X = startPoint.X;
rectCropArea.Y = e.Y;
} else {
rectCropArea.Width = startPoint.X - e.X;
rectCropArea.Height = startPoint.Y - e.Y;
rectCropArea.X = e.X;
rectCropArea.Y = e.Y;
}
PictureBox1.Refresh();
}
}
private void PicBox_Paint(System.Object sender, System.Windows.Forms.PaintEventArgs e)
{
Pen drawLine = new Pen(Color.Red);
drawLine.DashStyle = DashStyle.Dash;
e.Graphics.DrawRectangle(drawLine, rectCropArea);
}
private void btnCrop_Click(System.Object sender, System.EventArgs e)
{
PictureBox2.Refresh();
Bitmap sourceBitmap = new Bitmap(PictureBox1.Image, PictureBox1.Width, PictureBox1.Height);
Graphics g = PictureBox2.CreateGraphics();
if (!(CheckBox1.Checked)) {
g.DrawImage(sourceBitmap, new Rectangle(0, 0, PictureBox2.Width, PictureBox2.Height), rectCropArea, GraphicsUnit.Pixel);
sourceBitmap.Dispose();
} else {
int x1 = 0;
int x2 = 0;
int y1 = 0;
int y2 = 0;
try {
x1 = Convert.ToInt32(CX1.Text);
x2 = Convert.ToInt32(CX2.Text);
y1 = Convert.ToInt32(CY1.Text);
y2 = Convert.ToInt32(CY2.Text);
} catch (Exception ex) {
MessageBox.Show("Enter valid Coordinates (only Integer values)");
}
if (((x1 < x2 & y1 < y2))) {
rectCropArea = new Rectangle(x1, y1, x2 - x1, y2 - y1);
} else if ((x2 < x1 & y2 > y1)) {
rectCropArea = new Rectangle(x2, y1, x1 - x2, y2 - y1);
} else if ((x2 > x1 & y2 < y1)) {
rectCropArea = new Rectangle(x1, y2, x2 - x1, y1 - y2);
} else {
rectCropArea = new Rectangle(x2, y2, x1 - x2, y1 - y2);
}
PictureBox1.Refresh();
//This repositions the dashed box to new location as per coordinates entered.
g.DrawImage(sourceBitmap, new Rectangle(0, 0, PictureBox2.Width, PictureBox2.Height), rectCropArea, GraphicsUnit.Pixel);
sourceBitmap.Dispose();
}
}
private void pictureBox1_MouseClick(System.Object sender, System.Windows.Forms.MouseEventArgs e)
{
PictureBox1.Refresh();
}
private void CheckBox1_CheckedChanged(System.Object sender, System.EventArgs e)
{
if ((CheckBox1.Checked)) {
CX1.Visible = true;
Label10.Visible = true;
CY1.Visible = true;
Label9.Visible = true;
CX2.Visible = true;
Label8.Visible = true;
CY2.Visible = true;
Label7.Visible = true;
X1.Text = "0";
X2.Text = "0";
Y1.Text = "0";
Y2.Text = "0";
} else {
CX1.Visible = false;
Label10.Visible = false;
CY1.Visible = false;
Label9.Visible = false;
CX2.Visible = false;
Label8.Visible = false;
CY2.Visible = false;
Label7.Visible = false;
}
}
public Form1()
{
Load += OnLoad;
}
}

To copy a free-form selection you need to work with polygons.
Here is a complete example. Just paste this into a new solution and try it out (just change the path to the images).
It will create 2 pictureboxes and load an image into the first one and also create an image. Then you can click on the first image and when you have clicked 2 times it will start to show a selection, when you are finished just press the button and it will copy the selection to the other pictureBox and then save it as an png image.
What it does is to create a brush from the first image and then paint the polygon onto another image and set the other pixels in the rectangle to a background color of your choice, in this case the color: Color.Transparent.
Example:
public partial class Form1 : Form {
private List<Point> _points = new List<Point>();
private PictureBox _pictureBox1;
private PictureBox _pictureBox2;
private Button _button1;
public Form1() {
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e) {
Size = new Size(1366, 675);
_pictureBox1 = new PictureBox {
Location = new Point(12, 51),
Size = new Size(651, 474),
BorderStyle = BorderStyle.FixedSingle
};
_pictureBox2 = new PictureBox
{
Location = new Point(669, 51),
Size = new Size(651, 474),
BorderStyle = BorderStyle.FixedSingle
};
_button1 = new Button {
Text = #"Copy selected area",
Location = new Point(13, 13),
Size = new Size(175, 23)
};
Controls.AddRange(new Control[] { _pictureBox1, _pictureBox2, _button1 });
_pictureBox1.Image = Image.FromFile(#"d:\temp\Hopetoun_falls.jpg");
_points = new List<Point>();
_pictureBox1.MouseDown += delegate(object o, MouseEventArgs args) { _points.Add(args.Location); _pictureBox1.Refresh(); };
_pictureBox1.Paint += pictureBox1_Paint;
_button1.Click += button_Click;
}
private void pictureBox1_Paint(object sender, PaintEventArgs e) {
if (_points.Count < 2) {
return;
}
var max = _points.Count;
for (int i = 1; i < max; i++) {
e.Graphics.DrawLine(Pens.Red, _points[i-1].X, _points[i-1].Y, _points[i].X, _points[i].Y);
}
e.Graphics.DrawLine(Pens.Red, _points[max - 1].X, _points[max - 1].Y, _points[0].X, _points[0].Y);
}
private static Bitmap GetSelectedArea(Image source, Color bgColor, List<Point> points) {
var bigBm = new Bitmap(source);
using (var gr = Graphics.FromImage(bigBm)) {
// Set the background color.
gr.Clear(bgColor);
// Make a brush out of the original image.
using (var br = new TextureBrush(source)) {
// Fill the selected area with the brush.
gr.FillPolygon(br, points.ToArray());
// Find the bounds of the selected area.
var sourceRect = GetPointListBounds(points);
// Make a bitmap that only holds the selected area.
var result = new Bitmap(sourceRect.Width, sourceRect.Height);
// Copy the selected area to the result bitmap.
using (var resultGr = Graphics.FromImage(result)) {
var destRect = new Rectangle(0, 0, sourceRect.Width, sourceRect.Height);
resultGr.DrawImage(bigBm, destRect, sourceRect, GraphicsUnit.Pixel);
}
// Return the result.
return result;
}
}
}
private static Rectangle GetPointListBounds(List<Point> points) {
int xmin = points[0].X;
int xmax = xmin;
int ymin = points[0].Y;
int ymax = ymin;
for (int i = 1; i < points.Count; i++) {
if (xmin > points[i].X) xmin = points[i].X;
if (xmax < points[i].X) xmax = points[i].X;
if (ymin > points[i].Y) ymin = points[i].Y;
if (ymax < points[i].Y) ymax = points[i].Y;
}
return new Rectangle(xmin, ymin, xmax - xmin, ymax - ymin);
}
private void button_Click(object sender, EventArgs e) {
if (_points.Count < 3) {
return;
}
var img = GetSelectedArea(_pictureBox1.Image, Color.Transparent, _points);
_pictureBox2.Image = img;
_pictureBox2.Image.Save(#"d:\temp\sample.png", ImageFormat.Png);
}
}

Moving Bitlines takes snapshot of background image with it in panel in C#

I am working on a project where I have to align series of images so for that I use lines created using bitmap. Now user can move and rotate this line in anywhere inside panel which has that image as background. Now I have already tried to make panel double buffered which solves the problem of background snapshot while rotating, but when I move that line it takes a piece of background with it. I also tried to refresh panel but that's not working.
Heres the code:
private bool _rotating;
private bool _dragging;
private int _clickX;
private int _clickY;
private Point _clickCoords;
private int _middleX;
private int _middleY;
private int _centerX;
private int _centerY;
private double _radius;
private DateTime lastRotate = DateTime.Today;
public void UpdateCircle(Line l)
{
_centerX = (l.EndPoint.X + l.StartPoint.X) / 2 + l.Left;
_centerY = (l.EndPoint.Y + l.StartPoint.Y) / 2 + l.Top;
_radius = GetDistance(l.StartPoint.X, l.StartPoint.Y, l.EndPoint.X, l.EndPoint.Y) / 2;
// panel5.Refresh();
}
public void UpdateMiddle(Line l)
{
_middleX = (l.EndPoint.X + l.StartPoint.X) / 2;
_middleY = (l.EndPoint.Y + l.StartPoint.Y) / 2;
// panel5.Refresh();
}
public double GetDistance(double x1, double y1, double x2, double y2)
{
return Math.Sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
public void LineMouseDown(object sender, MouseEventArgs e)
{
var l = (Line)sender;
if (GetDistance(e.X, e.Y, l.StartPoint.X, l.StartPoint.Y) < 30 ||
GetDistance(e.X, e.Y, l.EndPoint.X, l.EndPoint.Y) < 30)
{
_rotating = true;
}
else
{
_dragging = true;
panel5.Refresh();
}
_clickX = e.X;
_clickY = e.Y;
panel5.Refresh();
_clickCoords = new Point(l.Left + e.X, l.Top + e.Y);
UpdateCircle(l);
UpdateMiddle(l);
// panel5.Refresh();
}
public void LineMouseUp(object sender, MouseEventArgs e)
{
_rotating = false;
_dragging = false;
panel5.Refresh();
}
public void LineMouseMove(object sender, MouseEventArgs e)
{
// panel5.Refresh();
var l = (Line)sender;
if (_rotating)
{
if ((DateTime.Now - lastRotate).TotalMilliseconds > 60)
{
try
{
var angle = GetAngle(l.Left + e.X, l.Top + e.Y, _centerX, 0, _centerX, _centerY);
var newStartPoint = new Point(
(int)Math.Round(_middleX + _radius * Math.Sin(angle)),
(int)Math.Round(_middleY + _radius * Math.Cos(angle))
);
var newEndPoint = new Point(2 * _middleX - newStartPoint.X, 2 * _middleY - newStartPoint.Y);
l.SetPoints(newStartPoint, newEndPoint);
UpdateMiddle(l);
lastRotate = DateTime.Now;
}
catch
{
//ignored
}
}
}
else if (_dragging)
{
l.Left = l.Left + e.X - _clickX;
l.Top = l.Top + e.Y - _clickY;
// panel5.Refresh();
}
}
public double GetAngle(int x2, int y2, int x1, int y1, int x0, int y0)
{
double angle = Math.Atan2(y1 - y0, x1 - x0) - Math.Atan2(y2 - y0, x2 - x0);
return angle;
}
And heres how I create lines:
bitLine = new Line { LineColor = Color.Red, LineWidth = 2, StartPoint = new Point(x1, y1), EndPoint = new Point(x2, y2) };
bitLine2 = new Line { LineColor = Color.Red, LineWidth = 2, StartPoint = new Point(x1, y1), EndPoint = new Point(x2, y2) };
//bitLine.Cursor = Cursors.SizeAll;
bitLine.MouseDown += LineMouseDown;
bitLine.MouseUp += LineMouseUp;
bitLine.MouseMove += LineMouseMove;
bitLine2.MouseDown += LineMouseDown;
bitLine2.MouseUp += LineMouseUp;
bitLine2.MouseMove += LineMouseMove;
bitLine2.Click += bitLine2_Click;
bitLine.Click += bitLine_Click;
panel5.Controls.Add(bitLine);
panel5.Controls.Add(bitLine2);
pb.WireControl(bitLine);
pb.WireControl(bitLine2);
bitLine.Location = Program.line1_location;
bitLine2.Location = Program.line2_location;
So please any suggestions will be helpful. I am really stuck in this.
Here is screenshot of what is the problem

Emgu cv Perspective Transform

I'm working emgucv project, But I have problem.
I want as a result of this image
I accept the four input coordinates and want to Perspective with a new image.
But my code is impossible...
This is my code:
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
Image<Bgr, byte> image = new Image<Bgr, byte>(#"C:\Users4.jpg");
Bitmap bitImage;
ImageConverter im = new ImageConverter();
int w, h;
int count = 4;
int a = 0;
HomographyMatrix homography;
PointF[] spoint = new PointF[4];
PointF[] dpoint = new PointF[4];
public Form1()
{
InitializeComponent();
}
private void Form1_Shown(object sender, EventArgs e)
{
bitImage = new Bitmap(#"C:\Users4.jpg");
w = bitImage.Width;
h = bitImage.Height;
this.Size = new System.Drawing.Size(w, h);
ibCanvas.BackgroundImage = bitImage;
}
/*
When taking the mouse coordinates being the X and Y axes to the coordinates stored in the Point array.
*/
private void ibCanvas_MouseDown(object sender, MouseEventArgs e)
{
if (count != 0)
{
spoint[a] = new PointF(e.X, e.Y);
a++;
count -= 1;
}
if (count == 0)
{
count = 4;
a = 0;
PointF[] pts1 = new PointF[4];
PointF[] pts2 = new PointF[4];
label1.Text = spoint[0].ToString();
label2.Text = spoint[1].ToString();
label3.Text = spoint[2].ToString();
label4.Text = spoint[3].ToString();
double w1 = Math.Sqrt(Math.Pow(spoint[3].X - spoint[0].X, 2)
+ Math.Pow(spoint[3].X - spoint[0].X, 2));
double w2 = Math.Sqrt(Math.Pow(spoint[2].X - spoint[1].X, 2)
+ Math.Pow(spoint[2].X - spoint[1].X, 2));
double h1 = Math.Sqrt(Math.Pow(spoint[3].Y - spoint[2].Y, 2)
+ Math.Pow(spoint[3].Y - spoint[2].Y, 2));
double h2 = Math.Sqrt(Math.Pow(spoint[0].Y - spoint[1].Y, 2)
+ Math.Pow(spoint[0].Y - spoint[1].Y, 2));
double maxWidth = (w1 < w2) ? w1 : w2;
double maxHeight = (h1 < h2) ? h1 : h2;
dpoint[0].X = 0;
dpoint[0].Y = 0;
dpoint[1].X = 0;
dpoint[1].Y = ((float)maxHeight-1);
dpoint[2].X = ((float)maxWidth - 1); ;
dpoint[2].Y = ((float)maxHeight - 1); ;
dpoint[3].X = ((float)maxWidth - 1); ;
dpoint[3].Y = 0;
homography = CameraCalibration.GetPerspectiveTransform(spoint, dpoint);
Image<Bgr, byte> newImage = image.WarpPerspective(homography, Emgu.CV.CvEnum.INTER.CV_INTER_CUBIC, Emgu.CV.CvEnum.WARP.CV_WARP_DEFAULT, new Bgr(0, 0, 0));
CvInvoke.cvShowImage("new Image", newImage);
}
}
}
}
I want really solve this problem
Please Help me!

Mandelbrot Conversion [closed]

Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
Improve this question
I'm receiving no errors but when I'm running it I'm also unable to see the Mandelbrot it just displays the grey box, I'm currently stuck at this one point thanks for any help, if you see any other parts of my code which contains grammar or coding errors it would be much appreciated if you told me.
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 System.Drawing.Drawing2D;
namespace SE_Fractal_Assignment
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
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(h, 0), 255);
this.b = Math.Min(Math.Max(h, 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 / 60f + 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 goal
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 picture1;
private System.Drawing.Bitmap bitmap;
private Graphics g1;
private Cursor c1, c2;
private HSBColor HSBcol = new HSBColor();
// private HSB HSBcol = new HSB();
private void Form1_Paint(object sender, PaintEventArgs e)
{
g1 = e.Graphics;
g1.DrawImage(bitmap, 0, 0, x1, y1);
g1.Dispose();
}
private void Form1_Load(object sender, EventArgs e)
{
init();
start();
}
public void init()
{
//HSBcol = new HSB();
finished = false;
c1 = Cursors.WaitCursor;
c2 = Cursors.Cross;
x1 = 640;
y1 = 480;
xy = (float)x1 / (float)y1;
bitmap.SetPixel(x1, y1, Color.Blue);
g1 = Graphics.FromImage(bitmap);
finished = true;
// xy = (float)x1 / (float)y1;
//picture = createImage(x1, y1);
//g1 = picture.getGraphics();
}
public void destroy() // delete all instances
{
if (finished)
{
//removeMouseListener(this);
//removeMouseMotionListener(this);
//bitmap = null;
g1 = null;
c1 = null;
c2 = null;
//System.gc(); // garbage collection
GC.Collect();
}
}
public void start()
{
action = false;
rectangle = false;
initvalues();
xzoom = (xende - xstart) / (double)x1;
yzoom = (yende - ystart) / (double)y1;
mandelbrot();
}
public void stop()
{
}
public void paint(Graphics g)
{
update(g);
}
public void update(Graphics g)
{
/* Pen myPen = new Pen(Color.White);
g.DrawImage(bitmap, 0, 0);
if (rectangle)
{
if (xs < xe)
{
if (ys < ye)
{
g.DrawRectangle(myPen, xs, ys, (xe - xs), (ye - ys));
}
}
else
{
g.DrawRectangle(myPen, xs, ys, (xe - xs), (ye - ys));
}
myPen.Dispose();
}*/
}
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
///djm added
///HSBcol.fromHSB(h,0.8f,b);
///
//convert hsb to rgb then make a Java Color
Color color = HSBColor.FromHSB(new HSBColor(h * 255, 0.8f * 255, b * 255));
///g1.setColor(col);
//djm end
//djm added to convert to RGB from HSB
//g1.setColor(Color.getHSBColor(h, 0.8f, b));
//djm test
// Color col = Color.FromArgb(0, 0, 0, 0);
//red = Color.Red;
// green = Color.Green;
// blue = Color.Blue;
//djm
alt = h;
}
Pen pen = new Pen(Color.Aqua);
g1.DrawLine(pen, x, y, x + 1, y);
}
//showStatus("Mandelbrot-Set ready - please select zoom area with pressed mouse.");
//setCursor(c2);
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 Form1_paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
g1 = g;
action = false;
rectangle = false;
initvalues();
xzoom = (xende - xstart) / (double)x1;
yzoom = (yende - ystart) / (double)y1;
//picture = g.DrawImage;
//g.DrawImage(picture,0,0);
update(g);
mandelbrot();
}
private void Form1_MouseDown(object sender, MouseEventArgs e)
{
if (action)
{
xs = e.X;
ys = e.Y;
}
}
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
// e.consume();
if (action)
{
xe = e.X;
ye = e.Y;
rectangle = true;
//repaint();
}
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
rectangle = false;
}
private void Form1_Click(object sender, MouseEventArgs e)
{
}
public String getAppletInfo()
{
return "fractal.class - Mandelbrot Set a Java Applet by Eckhard Roessel 2000-2001";
}
}
}

Honestly, the code is so cluttered and disorganized, it's hard to know all of what might be wrong with it. Sorry to be so blunt.
That said, a couple of obvious problems I see involving your "g1" Graphics instance member.
First, you are using the same field for two purposes: when computing the original image, you expect this to be a Graphics instance you can use to draw into your bitmap. But in the Paint event, you set it to the Graphics instance for the window, into which the painting should be done.
Second, in that Paint event, you dispose the Graphics instance before you return. But the instance you're disposing isn't yours. It belongs to the Forms system, and the only thing you should be doing with it is drawing into it.
There actually appear to be two different Paint event handlers and it's not clear which one you're using. You only dispose the Graphics instance in one of those places, so that may or may not be the real problem.
Personally, I would break the problem down into different elements. For a relative novice, it can be hard enough just to correctly draw a bitmap. It can also be difficult to really grasp how Paint event handling should be done. And of course, there's the Mandelbrot computations themselves. Trying to implement all three things (and more) at the same time can be overwhelming, and will take a lot longer assuming you can figure it out at all.
I would start by writing a simple program that just has a single PictureBox, which when you click a button, your program creates a new Bitmap object, into which you draw something simple (say, a rectangle, circle, or maybe just some text) and then assigns that Bitmap object to the PictureBox.Image property.
Once you have that working, then you can change the drawing part of the code to draw a Mandelbrot image instead.
Finally, once you have that working, then you can work on using the Paint event to draw the bitmap into your window directly instead of using the PictureBox control (the main reason for wanting to do this would presumably be that you eventually want to update the image as it's being drawn...if you only want to show it at the very end, then IMHO the PictureBox is a better approach).