Example Application: The Color Selector

Introduction

Microsoft Windows provides a function used to get a color stored in a pixel. The .NET Framework supports this operation in the Bitmap class, which is equipped with a method named GetPixel. By calling this method, you can retrieve the color of a pixel.

Practical Learning: Creating the Application

1. Start Microsoft Visual Studio
2. To create a new program, on the main menu, click File -> New Project...
3. In the middle list, click Windows Application
4. Set the Name to ColorSelector1 and click OK
5. Copy the following picture and paste it somewhere in your computer
   

   

6. Design the form as follows:
    

   

   Control		Text	Name	Other Properties
   PictureBox			pbxColor	Image: colorpal1.jpg
   Label		Red:
   TextBox			txtRed
   Label		Green:
   TextBox			txtGreen
   Label		Blue:
   TextBox			txtBlue
   Panel			pnlPreview	BorderStyle: FixedSingle
   Button		Close	btnClose

7. Right-click the form and click View Code
8. Above the public Form1() line, declare a Boolean variable named IsSelecting:
   

   using System;
   using System.Collections.Generic;
   using System.ComponentModel;
   using System.Data;
   using System.Drawing;
   using System.Linq;
   using System.Text;
   using System.Windows.Forms;
   
   namespace ColorSelector1
   {
       public partial class Form1 : Form
       {
           bool isSelecting;
   
           public Form1()
           {
               InitializeComponent();
           }
       }
   }

9. Return to the form and double-click an unoccupied area of its body
10. Implement the event as follows:
    

    private void Form1_Load(object sender, EventArgs e)
    {
                isSelecting = false;
    }

11. Return to the form and click the picture box control on it
12. In the Properties window, click the Events button and double-click MouseDown
13. Implement the event as follows:
    

    private void pbxColor_MouseDown(object sender, MouseEventArgs e)
    {
                isSelecting = true;
    }

14. Return to the form and click the picture box control on it
15. In the Events section of the Properties window, double-click MouseUp and implement the event as follows:
    

    private void pbxColor_MouseUp(object sender, MouseEventArgs e)
    {
                isSelecting = false;
    }

16. Return to the form and click the picture box control on it
17. In the Events section of the Properties window, double-click MouseMove and implement the event as follows:
    

    private void pbxColor_MouseMove(object sender, MouseEventArgs e)
    {
            if (isSelecting == true)
            {
                    Bitmap bmpImage = (Bitmap)pbxColor.Image;
                    Color clr = bmpImage.GetPixel(e.X, e.Y);
    
                    txtRed.Text = clr.R.ToString();
                    txtGreen.Text = clr.G.ToString();
                    txtBlue.Text = clr.B.ToString();
    
                    pnlPreview.BackColor = clr;
            }
    }

18. Execute the application
19. Click the mouse on the picture mouse and drag to produce a color
     
    
20. Close the form