How to save drawn shapes as images c#

Question

I am creating a painting program, I have figured out how to draw shapes to the Form, but how do I save them, I tried to do this:

Image bmp = new Bitmap(this.Width - panel1.Width, this.Height - panel1.Height);
using (Graphics g = Graphics.FromImage(bmp))
{

}
bmp.Save("test.bmp"); 

It saves test.bmp but the file is empty?

Heres is my entire code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Paint_Program
{

public partial class PaintImg : Form
{



    public Boolean veryimportantbool = false;
    int drawcount = 0;
    int brushsize = 16;

    public PaintImg()
    {
        InitializeComponent();
        //Cursor drawCursor = new Cursor("Pencil.cur");
        //this.Cursor = drawCursor;


    }


    private void Form1_Load(object sender, EventArgs e)
    {


        //Cursor.Position = new Point(this.Location.X - this.Width / 2, this.Location.Y - this.Height / 2)
        UserControl1 userc1 = new UserControl1();
        userc1.Show();
        brushsize = Convert.ToInt16(label1.Text);


    }

    private void rectangleShape1_Click(object sender, EventArgs e)
    {

    }

    private void Test_Click(object sender, EventArgs e)
    {
        //testing 
        //Console.WriteLine("X:" + mousex);
        //onsole.WriteLine("Y: " + mousey);
    }

    private void Form1_SizeChanged(object sender, EventArgs e)
    {

    }


    public void Form1_MouseClick(object sender, MouseEventArgs i)
    {

            drawcount = drawcount + 1;
            System.Drawing.SolidBrush myBrush = new System.Drawing.SolidBrush(System.Drawing.Color.Red);
            System.Drawing.Graphics formGraphics;
            formGraphics = this.CreateGraphics();
            formGraphics.FillRectangle(myBrush, new Rectangle(i.X, i.Y, brushsize, brushsize));
            myBrush.Dispose();
            formGraphics.Dispose();
            count.Text = Convert.ToString(drawcount);


    }

    private void newToolStripButton_Click(object sender, EventArgs e)
    {
        //SetupDoc newsetup = new SetupDoc();
        //newsetup.ShowDialog();
    }

    private void PaintImg_MouseMove(object sender, MouseEventArgs e)
    {

    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {

    }

    private void panel1_Click(object sender, MouseEventArgs e)
    {
        drawcount = drawcount + 1;
        System.Drawing.SolidBrush myBrush = new      System.Drawing.SolidBrush(System.Drawing.Color.Red);
        System.Drawing.Graphics formGraphics;
        formGraphics = this.CreateGraphics();
        formGraphics.FillRectangle(myBrush, new Rectangle(e.X, e.Y, brushsize, brushsize));
        myBrush.Dispose();
        formGraphics.Dispose();
        count.Text = Convert.ToString(drawcount);
    }

    private void label1_Click(object sender, EventArgs e)
    {

    }

    private void button1_Click(object sender, EventArgs e)
    {
        brushsize = brushsize + 1;
        label1.Text = Convert.ToString(brushsize);
    }

    private void button2_Click(object sender, EventArgs e)
    {
        brushsize = brushsize - 1;
        label1.Text = Convert.ToString(brushsize);
    }

    private void button3_Click(object sender, EventArgs e)
    {
        Image bmp = new Bitmap(this.Width - panel1.Width, this.Height - panel1.Height);
        using (Graphics g = Graphics.FromImage(bmp))
        {

        }
        bmp.Save("test.bmp");
    }

}
}

I would appreicate it if anyone new how to do this???? :D

Answer 1

Bitmap bmp;
Graphics objGraphics;
Rectangle rt;
Point pnt;

rt = this.ClientRectangle;
pnt = this.PointToScreen(new Point(0, 0));

bmp = new Bitmap(rt.Width, rt.Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);

objGraphics = Graphics.FromImage(bmp);
objGraphics.CopyFromScreen(pnt.X, pnt.Y, 0, 0, rt.Size, CopyPixelOperation.SourceCopy);
objGraphics.Dispose();

bmp.Save("test.bmp");

bmp.Dispose();

valter

Answer 2

There is nothing wrong with code you've posted - it draws exactly what you've coded - nothing. It creates nice empty file with size you've specified (which could be wrong depending one the parameters you've passed).

To get something to show up on the bitmap you need to draw - i.e. refactor code from panel1_Click to draw, or at least hardcode something:

Image bmp = new Bitmap(20, 20);
using (Graphics g = Graphics.FromImage(bmp))
{
   g.FillRectangle(new SolidBrush(Color.Red), new Rectangle(3, 3, 8, 8));
}
bmp.Save("test.bmp");