如何用鼠标画图？

Question

I want to make a simple mspaint. Firstly, I draw lines in the mouse event.

private void pnl_Draw_MouseMove(object sender, MouseEventArgs e)
{
    if(startPaint)
    {
        g = pnl_Draw.CreateGraphics();
        g.DrawLine(p, new Point(initX ?? e.X, initY ?? e.Y), new Point(e.X, e.Y));
        initX = e.X;
        initY = e.Y;
    }
}

And then, I realized that all would be resolved if the form was minimized. However, How do I use the onpaint event to do it? Should I store all the points in a list when the user click and move, and then paint and clear them in the onpaint event?

Answer 1

You need to keep a copy of the last image as a bitmap object. Everything user does should update this object in the memory. You can also handle OnPaint event of your canvas to display this bitmap object as a background image.