C# - Drawing Circles using Pixel by Pixel

---

Drawing Circle is not difficult by using built in function. But if you would like to draw circle pixel by pixel by calculating each cordinates, you can use the formula x + r cos(a) and y + r sin (a).

Source Code

void PutPixel(Graphics g, int x, int y, Color c)

{

      Bitmap bm = new Bitmap(1, 1);

      bm.SetPixel(0, 0, Color.Red);

      g.DrawImageUnscaled(bm, x, y);

}

private void Form1_Paint(object sender, PaintEventArgs e)

{  

      Graphics myGraphics = e.Graphics;

      myGraphics.Clear(Color.White);

      double radius = 5;

      for (int j = 1; j <= 25; j++)

      {

            radius = (j + 1) * 5;

            for (double i = 0.0; i < 360.0; i += 0.1)

            {

            double angle = i * System.Math.PI / 180;

             int x = (int)(150 + radius * System.Math.Cos(angle));

             int y = (int)(150 + radius * System.Math.Sin(angle));

             PutPixel(myGraphics, x, y, Color.Red);

            //System.Threading.Thread.Sleep(1); // If you want to draw circle very slowly.

            }

      }

      myGraphics.Dispose();

}

Output