Change color in paint

Question

I have coded a program that will allow user to paint with pen in the Form. But there is a problem.

I can set just 2 color in the form e.g. I set Black color for left buttons and red color for right buttons.

Everything I need is how can I change this code to a code which user can choose his own Color.

I tried different ways like Color Dialogue but I couldn't.

My code:

private void Form1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        Graphics graphic = this.CreateGraphics();
        graphic.DrawLine(Pens.Black, e.X, e.Y, e.X + 1, e.Y + 1);
    }

    if (e.Button == System.Windows.Forms.MouseButtons.Right)
    {
        Graphics graphic = this.CreateGraphics();
        graphic.DrawLine(Pens.Red, e.X, e.Y, e.X + 1, e.Y + 1);
    }
}

Answer 1

Use some dialog to select a colour for left and right mouse buttons and store that in a class level variable i.e.

if (_leftPen != null) { _leftPen.Dispose(); }
_leftPen = new Pen(selectedColour, 1f);

Note that 1f is the thickness of the Pen, this can be changed to meet your requirements.

Then in your drawing method just use _leftPen. Then just apply similar logic for the right mouse button i.e. _rightPen. You then have:

private Pen _leftPen = Pens.Black;
private Pen _rightPen = Pens.Red;

private void Form1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        Graphics graphic = this.CreateGraphics();
        graphic.DrawLine(_leftPen, e.X, e.Y, e.X + 1, e.Y + 1);
    }

    if (e.Button == System.Windows.Forms.MouseButtons.Right)
    {
        Graphics graphic = this.CreateGraphics();
        graphic.DrawLine(_rightPen, e.X, e.Y, e.X + 1, e.Y + 1);
    }
}

All you need to do is find a way for the user to select their own colour.

Also note the comment by @Taw:

Winforms graphics basic rule #1 : Never use control.CreateGraphics! Never try to cache a Graphics object! Either draw into a Bitmap bmp using a Graphics g = Graphics.FromImage(bmp) or in the Paint event of a control, using the e.Graphics parameter..The system needs to draw all the controls' surfaces at times you can't control; therefore all you want to add to those surfaces must be created from the one event that the system will call, which is the Paint event.

You should use your code in the Paint event and in the MouseMove event you should store the positions of the line that you want to draw then update this later.

private Pen _leftPen = Pens.Black;
private Pen _rightPen = Pens.Red;

private List<Point> _leftPoints = new List<Point>();
private List<Point> _rightPoints = new List<Point>();

private void Form1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        _leftPoints.Add(new Point(e.X, e.Y));
    }

    if (e.Button == System.Windows.Forms.MouseButtons.Right)
    {
        _rightPoints.Add(new Point(e.X, e.Y));
    }

    this.Invalidate();
}

private void Form1_Paint(object sender, PaintEventArgs e)
{
    foreach (Point point in _leftPoints)
    {
        e.Graphics.DrawLine(_leftPen, point.X, point.Y, point.X + 1, point.Y + 1);
    }

    //Similar code for _rightPoints here
}

Note the call to Invalidate forces the form to repaint itself. If applicable you may use this.Refresh() or this.Update() instead.

Answer 2

Color BackColor = Color.Black;
Color ForeColor = Color.Red;

Then get user colors and set the Backcolor and Forecolor

      private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            Graphics graphic = this.CreateGraphics();
            graphic.DrawLine(new Pen(ForeColor), e.X, e.Y, e.X + 1, e.Y + 1);
        }
        if (e.Button == System.Windows.Forms.MouseButtons.Right)
        {
            Graphics graphic = this.CreateGraphics();
            graphic.DrawLine(new Pen(BackColor), e.X, e.Y, e.X + 1, e.Y + 1);
        }
    }

Answer 3

You can use something like this:

using System;
using System.Drawing;
using System.Windows.Forms;

public partial class Form1 : Form
{
    private readonly Graphics graphics;

    public Form1()
    {
        InitializeComponent();

        this.graphics = this.CreateGraphics();

        this.Load += (s, e) =>
        {
            foreach (var color in Enum.GetValues(typeof(KnownColor)))
                this.UserColors.Items.Add(color);
        };
    }

    /// <summary>
    /// Painting (left button use changed color, right-white to erase)
    /// </summary>
    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
            this.graphics.DrawLine(
                new Pen(
                    Color.FromKnownColor(
                        (KnownColor)Enum.Parse(typeof(KnownColor),
                        this.UserColors.SelectedItem.ToString()))),
                e.X,
                e.Y,
                e.X + 1,
                e.Y + 1);

        if (e.Button == MouseButtons.Right)
            this.graphics.DrawLine(
                Pens.White,
                e.X,
                e.Y,
                e.X + 1,
                e.Y + 1);
    }
}

Where this.UserColors is ComboBox on your main window.