Question

Can someone tell me what i don’t make as it should, why i cannot save the drawing to a physical storage?

    private void panel1_Paint(object sender, PaintEventArgs e)
    {
        Pen p = new Pen(Color.Red, 3);
        Bitmap bmp = new Bitmap(700, 900);
        Graphics gr = this.CreateGraphics();

        gr.DrawLine(p, new Point(30, 30), new Point(80, 120));
        gr.DrawEllipse(p, 30, 30, 80, 120);

       //when i do this way it saves only a black rectangle, without other drawn content
       bmp.Save(@"C:\testBMP.jpeg", ImageFormat.Jpeg);


       // If i use the following 2 commented lines it saves only a empty rectangle.

       //Rectangle rec = new Rectangle(0, 0, 700, 900);
       // panel1.DrawToBitmap(bmp, rec);


    }

Thank you for advice!

Answer 1

You have two problems here.

1. Drawing your panel’s contents. This should be done inside its Paint event handler, like this:

   private void panel1_Paint(object sender, PaintEventArgs e)
   {
       using (Pen p = new Pen(Color.Red, 3))
       {
           // get the panel's Graphics instance
           Graphics gr = e.Graphics;
   
           // draw to panel
           gr.DrawLine(p, new Point(30, 30), new Point(80, 120));
           gr.DrawEllipse(p, 30, 30, 80, 120);
       }
   }
   

2. Saving your panel’s contents as an image. This part should be done somewhere else (for example, when you click on a “Save” button):

   private void saveButton_Click(object sender, EventArgs e)
   {
        int width = panel1.Size.Width;
        int height = panel1.Size.Height;
   
        using (Bitmap bmp = new Bitmap(width, height))
        {
            panel1.DrawToBitmap(bmp, new Rectangle(0, 0, width, height));
            bmp.Save(@"C:\testBMP.jpeg", ImageFormat.Jpeg);
        }
   }