i am doing a program on the math "Problem of Apollonius". But first my program needs to be able to allow the users to draw three circles on a panel, the circles can differ from size and position.
I cant figure out how to allow the users to draw their on size circle on the panel. Any help would be greatly appreciated.
Here is a simple demonstration for Windows Forms.
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
// Definition for our ellipse object.
class Ellipse
{
public int PenWidth;
public Color Color;
public Rectangle Rectangle;
// Paint ourselves with the specified Graphics object
public void Draw(Graphics graphics)
{
using (Pen pen = new Pen(Color, PenWidth))
graphics.DrawEllipse(pen, Rectangle);
}
}
class Form1 : Form
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
public Form1()
{
// Remove "flickering" from the repainting.
SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.Opaque | ControlStyles.OptimizedDoubleBuffer | ControlStyles.ResizeRedraw | ControlStyles.UserPaint, true);
}
// Store all created ellipses so they can be rendered during the Paint event.
List<Ellipse> ellipses = new List<Ellipse>();
// Definition of an Ellipse under construction
class EllipseConstruction
{
public Point Origin;
public Ellipse Ellipse;
}
// Storage for ellipse under construction.
EllipseConstruction ellipseConstruction;
// Random number generator Ellipse creation.
private Random Rand = new Random();
// These are the possible ellipse colors
static readonly Color[] EllipseColors =
{
Color.Black,
Color.White,
Color.Red,
Color.Green,
Color.Blue,
Color.Yellow,
Color.Magenta,
Color.Cyan,
};
protected override void OnMouseDown(MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
// Capture mouse until button up.
Capture = true;
// Create a new Ellipse object and record the [X, Y] origin of this click
ellipseConstruction = new EllipseConstruction
{
Origin = e.Location,
Ellipse = new Ellipse { Color = EllipseColors[Rand.Next(EllipseColors.Length)], PenWidth = Rand.Next(1, 6) },
};
}
base.OnMouseDown(e);
}
protected override void OnMouseMove(MouseEventArgs e)
{
// If the mouse is captured, the user is creating a new Ellipse so we update its rectangle with the mouse coordinates
if (Capture)
UpdateEllipseUnderConstruction(e.Location);
base.OnMouseMove(e);
}
protected override void OnMouseUp(MouseEventArgs e)
{
if (Capture && e.Button == MouseButtons.Left)
{
// If the mouse is captured and it's the Left button being released, the user is
// done creating a new Ellipse.
// Stop capturing the mouse.
Capture = false;
// Final update of the Ellipse under construction
UpdateEllipseUnderConstruction(e.Location);
// Add the new Ellipse to our list unless its width or height are zero which would result in a non-visible ellipse
if (ellipseConstruction.Ellipse.Rectangle.Width > 0 && ellipseConstruction.Ellipse.Rectangle.Height > 0)
ellipses.Add(ellipseConstruction.Ellipse);
// Since we are done constructing a new Ellipse, we don't need the construction object
ellipseConstruction = null;
}
base.OnMouseUp(e);
}
protected override void OnKeyDown(KeyEventArgs e)
{
// Allow Ellipse creation to be cancelled with the Escape key
if (Capture && e.KeyData == Keys.Escape)
{
Capture = false; // End mouse capture
ellipseConstruction = null; // Remove construction ellipse
Invalidate(); // Notify operating system that we need to be repainted.
}
base.OnKeyDown(e);
}
private void UpdateEllipseUnderConstruction(Point point)
{
// Calculate new ellipse rectangle based on ellipseConstruction.Origin and point.
Point origin = ellipseConstruction.Origin;
int xRadius = Math.Abs(origin.X - point.X);
int yRadius = Math.Abs(origin.Y - point.Y);
// Make X and Y radii the same for a true circle unless the Shift key is held down
if ((ModifierKeys & Keys.Shift) == 0)
xRadius = yRadius = Math.Max(xRadius, yRadius);
ellipseConstruction.Ellipse.Rectangle = new Rectangle(origin.X - xRadius, origin.Y - yRadius, xRadius * 2, yRadius * 2);
Invalidate(); // Notify operating system that we need to be repainted.
}
protected override void OnPaint(PaintEventArgs e)
{
// Paint the background since we specified ControlStyles.AllPaintingInWmPaint and ControlStyles.Opaque.
e.Graphics.Clear(Color.SlateGray);
// Paint the ellipses we have stored.
foreach (Ellipse ellipse in ellipses)
ellipse.Draw(e.Graphics);
// If the user is creating a new ellipse paint it.
if (ellipseConstruction != null)
ellipseConstruction.Ellipse.Draw(e.Graphics);
base.OnPaint(e);
}
}
In some older technologies, you would have to erase and redraw the circle in the MouseMove event of step 2. If you are using WPF, or something similarly advanced, you can just create a circle object and add it to a canvas in step 1, and then manipulate its properties in step 2. The WPF engine will take care of erasing the circle from the old location and drawing it in the new location.
You can draw on all winforms control using Graphics. For example:
private void button1_Click(object sender, EventArgs e)
{
System.Drawing.Graphics g = System.Drawing.Graphics.FromHwnd(panel1.Handle);
g.DrawEllipse(Pens.Green, panel1.ClientRectangle);
}
But in this case your painting will disappear if the form is redrawn. So you need to do it in the OnPaint method. If want to force form redrawing you can simply call the Invalidate method of your form:
this.Invalidate();
Use Graphics.DrawEllipse method:
// Create pen.
Pen blackPen = new Pen(Color.Black, 3);
// Create rectangle for circle.
Rectangle rect = new Rectangle(0, 0, 100, 100);
// Draw circle.
e.Graphics.DrawEllipse(blackPen, rect);
Obtain a Graphics object from your surface on which you want to draw.
