Question

I found this small application that i’ve been playing around with for the past little while. I was wondering, if i wanted to simply rotate the image in a circle? or make the entire image just bounce up and down, how would i modify this program to do so? Everything i’ve tried will just stretch the image – even if i do get it to move to the left or to the right. Any ideas on what i can do? Code is below

   public partial class Form1 : Form
   {
          private int width = 15;
          private int height = 15;

          Image pic = Image.FromFile("402.png");
          private Button abort = new Button();
          Thread t;

          public Form1()
          {
            abort.Text = "Abort";
            abort.Location = new Point(190, 230);
            abort.Click += new EventHandler(Abort_Click);
            Controls.Add(abort);

            SetStyle(ControlStyles.DoubleBuffer| ControlStyles.AllPaintingInWmPaint| ControlStyles.UserPaint, true);

            t = new Thread(new ThreadStart(Run));
            t.Start();
          }
          protected void Abort_Click(object sender, EventArgs e) 
          {
            t.Abort();
          }

          protected override void OnPaint( PaintEventArgs e )   
          {
             Graphics g = e.Graphics;
             g.DrawImage(pic, 10, 10, width, height);
             base.OnPaint(e);
          }

          public void Run() 
          {

              while (true) 
              {
                for(int i = 0; i < 200; i++) 
                {
                    width += 5;

                  Invalidate();
                  Thread.Sleep(30);
                }

              }
          }
    }

Answer 1

So I don’t know what you’re trying to achieve, but to get the fundies out of the way, WinForms is a GDI+ library and its meant more for GUI stuff, so something like animation will probably be handled better by a graphics library like SFML.

Anyways, there’s a million ways to achieve what you want. In terms of moving something around in a circle, you’re gonna need a little simple trig. For a bouncing motion, I would say following a sine curve would be the easiest way.

Here’s some pseudo-code (not sure if this is syntax-perfect) for bouncing:

Field Definitions:

private double frame = 0;

OnPaint:

Graphics g = e.Graphics;
g.DrawImage(pic, 10, 10 + Math.sin(frame)*10, width, height);
frame+=.01;
base.OnPaint(e);

This way, every time the paint event is triggered, t will increase by .01 radians. The sin has a domain that will oscillate between -1 and 1, and you can multiply that by a factor of 10 to get that bouncing effect.

Frame represents your “keyframe”. If you want to speed it up, increase the frame+=__ to a higher value. If you want to increase the range, change the offset Math.sin(frame)*__