Drawing a rectangle in a picture - how to limit the area of ​​a rectangle?

Question

I draw a rectangle on the frame with mouse events:

private void StreamingWindow_MouseDown(object sender, MouseEventArgs e)
    {
              rect = new Rectangle(e.X, e.Y, 0, 0);
              this.Invalidate();       
    }

    private void StreamingWindow_Paint(object sender, PaintEventArgs e)
    {

       if (painting == true)
        {

            using (Pen pen = new Pen(Color.Red, 2))
            {
                e.Graphics.DrawRectangle(pen, rect);
            }
        }
    }

    private void StreamingWindow_MouseMove(object sender, MouseEventArgs e)
    {       
           if (e.Button == MouseButtons.Left)
           {
               // Draws the rectangle as the mouse moves
               rect = new Rectangle(rect.Left, rect.Top, e.X - rect.Left, e.Y - rect.Top);
           }
           this.Invalidate();     
    }

After drawing the rectangle, I can grab it inside and save as jpg.

What is my problem?

I can draw an edge whose borders are outside the image area:

How can I limit the area of ​​a rectangle whose border is the maximum allowable location of the rectangle?

Sorry for my English, I hope you understand my problem :) Therefore, I would like to have something like this:

Answer 1

private void StreamingWindow_MouseMove(object sender, MouseEventArgs e)
{       
  if (e.Button == MouseButtons.Left)
  {
    // Draws the rectangle as the mouse moves
    rect = new Rectangle(rect.Left, rect.Top, Math.Min(e.X - rect.Left, pictureBox1.ClientRectangle.Width - rect.Left), Math.Min(e.Y - rect.Top, pictureBox1.ClientRectangle.Height - rect.Top));
  }
  this.Invalidate();     
}

Answer 2

, , UX: MouseUp , BottomLeft , , "" , .

, , ,

    private void StreamingWindow_MouseUp(object sender, MouseEventArgs e)
    {
              if(rect.Right > myPictureBox.ClientRectangle.Right)
              {
                 rect.Width = myPictureBox.Right - rect.Left - someoffset;                     
              }       
              if(rect.Bottom > myPictureBox.ClientRectangle.Bottom)
              {
                 rect.Height= myPictureBox.Bottom - rect.Top - someoffset;                     
              }       
    }

- . .

Answer 3

-?

 rect = new Rectangle(min(e.X, pictureBoxX), min(e.Y, pictureBoxY), 0, 0);

pictureX pictureY .

Answer 4

pictureBox.

private void StreamingWindow_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            if (e.X < StreamingWindow.Width && Math.Abs(e.Y) < StreamingWindow.Height)
                // Draws the rectangle as the mouse moves
                rect = new Rectangle(rect.Left, rect.Top, e.X - rect.Left, e.Y -rect.Top);
        }
        this.Invalidate();
    }

-