Gamma correction

Gamma correction, or often simply gamma, is the name of a nonlinear operation used to code and decode luminance or tristimulus values in video or still image systems. It is very useful if you want to set the dark regions of a picture lighter or even darker. In this tutorial you will be shown how to create a gamma filter using OZEKI Camera SDK.

Important: you should study this article in order to find out how to setup your Windows Forms Application correctly.

Properties

Gamma: we can set the value of the contrast which is between 0.10 and 5 If you choose a low amount, the effect makes the difference smaller between the dark and light parts. If you choose a bigger value, the effect makes the difference bigger.

Figure 1 - Original image

Figure 2 - Modified image with gamma correction

using System;
using System.Windows.Forms;
using Ozeki.Camera;
using Ozeki.Media;

namespace ImageManipulation_WF
{
    public partial class MainForm : Form
    {
        private ICamera _camera;
        private DrawingImageProvider _imageProvider;
        private MediaConnector _connector;

        private ImageManipulation _manipulation;
        private OzGammaCorrection _filter;

        public MainForm()
        {
            InitializeComponent();

            _connector = new MediaConnector();
            _imageProvider = new DrawingImageProvider();
            // Create video viewer UI control

            // Bind the camera image to the UI control
            videoViewer.SetImageProvider(_imageProvider);

            _manipulation = new ImageManipulation();
            _manipulation.Start();

            _filter = new OzGammaCorrection();
        }

        private void btn_Connect_Click(object sender, EventArgs e)
        {
            _camera = new WebCamera();

            if (_camera == null) return;

            _connector.Connect(_camera.VideoChannel, _manipulation);
            _connector.Connect(_manipulation, _imageProvider);

            _camera.Start();
            videoViewer.Start();
        }

        private void btn_Add_Click(object sender, EventArgs e)
        {
            _manipulation.Add(_filter);
        }

        private void btn_Remove_Click(object sender, EventArgs e)
        {
            _manipulation.Remove(_filter);
        }

        private void factorTrack_Scroll(object sender, EventArgs e)
        {
            var trackBar = sender as TrackBar;
            if (trackBar != null)
            {
                var value = (double)(trackBar.Value) / 100;
                _filter.Gamma = value;
                lb_Level.Text = @"Gamma: " + value;
            }
        }
    }
}

GUI

namespace ImageManipulation_WF
{
    partial class MainForm
    {
        /// 

        /// Required designer variable.
        /// 
        private System.ComponentModel.IContainer components = null;

        /// 

        /// Clean up any resources being used.
        /// 
        /// true if managed resources should be disposed; otherwise, false.
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// 

        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// 
        private void InitializeComponent()
        {
            this.videoViewer = new Ozeki.Media.VideoViewerWF();
            this.btn_Connect = new System.Windows.Forms.Button();
            this.btn_Remove = new System.Windows.Forms.Button();
            this.btn_Add = new System.Windows.Forms.Button();
            this.lb_Level = new System.Windows.Forms.Label();
            this.trackBar = new System.Windows.Forms.TrackBar();
            ((System.ComponentModel.ISupportInitialize)(this.trackBar)).BeginInit();
            this.SuspendLayout();
            // 
            // videoViewer
            // 
            this.videoViewer.BackColor = System.Drawing.Color.Black;
            this.videoViewer.FlipMode = Ozeki.Media.FlipMode.None;
            this.videoViewer.FrameStretch = Ozeki.Media.FrameStretch.Uniform;
            this.videoViewer.FullScreenEnabled = true;
            this.videoViewer.Location = new System.Drawing.Point(12, 57);
            this.videoViewer.Name = "videoViewer";
            this.videoViewer.RotateAngle = 0;
            this.videoViewer.Size = new System.Drawing.Size(471, 334);
            this.videoViewer.TabIndex = 0;
            this.videoViewer.Text = "videoViewerWF1";
            // 
            // btn_Connect
            // 
            this.btn_Connect.Location = new System.Drawing.Point(12, 12);
            this.btn_Connect.Name = "btn_Connect";
            this.btn_Connect.Size = new System.Drawing.Size(152, 26);
            this.btn_Connect.TabIndex = 14;
            this.btn_Connect.Text = "Connect to WebCamera";
            this.btn_Connect.UseVisualStyleBackColor = true;
            this.btn_Connect.Click += new System.EventHandler(this.btn_Connect_Click);
            // 
            // btn_Remove
            // 
            this.btn_Remove.Location = new System.Drawing.Point(104, 475);
            this.btn_Remove.Name = "btn_Remove";
            this.btn_Remove.Size = new System.Drawing.Size(75, 23);
            this.btn_Remove.TabIndex = 1;
            this.btn_Remove.Text = "Remove";
            this.btn_Remove.UseVisualStyleBackColor = true;
            this.btn_Remove.Click += new System.EventHandler(this.btn_Remove_Click);
            // 
            // btn_Add
            // 
            this.btn_Add.Location = new System.Drawing.Point(23, 475);
            this.btn_Add.Name = "btn_Add";
            this.btn_Add.Size = new System.Drawing.Size(75, 23);
            this.btn_Add.TabIndex = 0;
            this.btn_Add.Text = "Add";
            this.btn_Add.UseVisualStyleBackColor = true;
            this.btn_Add.Click += new System.EventHandler(this.btn_Add_Click);
            // 
            // lb_Level
            // 
            this.lb_Level.AutoSize = true;
            this.lb_Level.Location = new System.Drawing.Point(20, 423);
            this.lb_Level.Name = "lb_Level";
            this.lb_Level.Size = new System.Drawing.Size(46, 13);
            this.lb_Level.TabIndex = 15;
            this.lb_Level.Text = "Gamma:";
            // 
            // trackBar
            // 
            this.trackBar.Location = new System.Drawing.Point(104, 423);
            this.trackBar.Maximum = 500;
            this.trackBar.Minimum = 1;
            this.trackBar.Name = "trackBar";
            this.trackBar.Size = new System.Drawing.Size(379, 45);
            this.trackBar.TabIndex = 16;
            this.trackBar.Value = 100;
            this.trackBar.Scroll += new System.EventHandler(this.factorTrack_Scroll);
            // 
            // MainForm
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(498, 520);
            this.Controls.Add(this.trackBar);
            this.Controls.Add(this.lb_Level);
            this.Controls.Add(this.btn_Remove);
            this.Controls.Add(this.btn_Add);
            this.Controls.Add(this.btn_Connect);
            this.Controls.Add(this.videoViewer);
            this.Name = "MainForm";
            this.Text = "Gamma correction";
            ((System.ComponentModel.ISupportInitialize)(this.trackBar)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private Ozeki.Media.VideoViewerWF videoViewer;
        private System.Windows.Forms.Button btn_Connect;
        private System.Windows.Forms.Button btn_Remove;
        private System.Windows.Forms.Button btn_Add;
        private System.Windows.Forms.Label lb_Level;
        private System.Windows.Forms.TrackBar trackBar;
    }
}
		

Related Pages

• Learn the basics about image manipulation in C#
• How to implement simple posterization in C#
• How to implement rotate filter in C#
• How to implement hue modifier in C#

Conclusion

With the help of this lecture you can successfully implement gamma correction with your C# camera application using the Ozeki Camera SDK.

FAQ

Below you can find the answers for the most frequently asked questions related to this topic:

1. What kind of developer environment is needed?

   • Microsoft Visual Studio 2010
   • Microsoft .Net Framework 4.0
   • Internet connection

2. How can I get the URL of the camera?

   You can get the URL from the producer of the camera.

3. I have not managed to build the solution. How to solve it?

   • Please set the Target framework property of the project to .NET 4.0.
   • You should add the OzekiSDK.dll to the references of the solution.
   • Please import the missing classes.