Champak's Blog: Accessing the Web Camera from a C# Windows Application.

In this application I will show how we can access the Web Camera on a Computer via a C# application.

To access the Web Camera, or other Video Capture Devices we need to use the avicap32.dll file.

I have developed a class called WebCamera to encapsulate the details of accessing the Camera. The details of the available devices will be displayed in a ListBox from which the user can select a device to use.

Here it is WebCamera.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace WebCamProject
{
    class WebCamera
    {
        private const int WM_CAP = 0x400;
        private const int WM_CAP_DRIVER_CONNECT = 0x40a;
        private const int WM_CAP_DRIVER_DISCONNECT = 0x40b;
        private const int WM_CAP_EDIT_COPY = 0x41e;
        private const int WM_CAP_SET_PREVIEW = 0x432;
        private const int WM_CAP_SET_OVERLAY = 0x433;
        private const int WM_CAP_SET_PREVIEWRATE = 0x434;
        private const int WM_CAP_SET_SCALE = 0x435;
        private const int WS_CHILD = 0x40000000;
        private const int WS_VISIBLE = 0x10000000;

        [DllImport("avicap32.dll")]
        protected static extern bool capGetDriverDescriptionA(int wDriverIndex, [MarshalAs(UnmanagedType.VBByRefStr)]ref String ldevicename, int namelength, [MarshalAs(UnmanagedType.VBByRefStr)] ref String deviceversion, int versionlength);
        [DllImport("avicap32.dll")]
        protected static extern int capCreateCaptureWindowA([MarshalAs(UnmanagedType.VBByRefStr)] ref string windowname,
            int style, int x, int y, int width, int height, int parent, int id);

        [DllImport("user32", EntryPoint = "SendMessageA")]
        protected static extern int SendMessage(int hwnd, int window, int x, [MarshalAs(UnmanagedType.AsAny)] object y);

        int deviceHandle;

        public static void LoadAllDevices(ListBox lstDevices)
        {
            String devicename = "".PadRight(100);
            String deviceversion = "".PadRight(100);
            lstDevices.Items.Clear();
            for (int i = 0; i <= 10; i++)
            {
                bool isDeviceReady = capGetDriverDescriptionA(i, ref devicename, 100, ref deviceversion, 100);
                if (!isDeviceReady)
                    continue;
                {
                    WebCamera d = new WebCamera(devicename, deviceversion);

                    lstDevices.Items.Add(d);
                }
            }

        }

        public System.Drawing.Image GetImage()
        {
            IDataObject data;
            System.Drawing.Image snapshot;

            SendMessage(deviceHandle, WM_CAP_EDIT_COPY, 0, 0);

            data = Clipboard.GetDataObject();
            if (data.GetDataPresent(typeof(System.Drawing.Bitmap)))
            {
                snapshot = (System.Drawing.Image)data.GetData(typeof(System.Drawing.Bitmap));
                return snapshot;
            }
            return null;
        }

        string devicename, deviceversion;

        public WebCamera(string devicename,string deviceversion)
        {
            this.devicename = devicename;
            this.deviceversion = deviceversion;

        }



        public override string ToString()
        {
            return "Device Name = " + this.devicename + " , Device Version = " + this.deviceversion;
        }

        public void StartWebCam(int height, int width, int handle,int deviceno)
        {
            string deviceIndex = "" + deviceno;
            deviceHandle = capCreateCaptureWindowA(ref deviceIndex, WS_VISIBLE | WS_CHILD, 0, 0, width, height, handle, 0);

            if (SendMessage(deviceHandle, WM_CAP_DRIVER_CONNECT, deviceno , 0) > 0)
            {
                SendMessage(deviceHandle, WM_CAP_SET_SCALE, -1, 0);
                SendMessage(deviceHandle, WM_CAP_SET_PREVIEWRATE, 0x42, 0);
                SendMessage(deviceHandle, WM_CAP_SET_PREVIEW, -1, 0);
            }
        }

             public void DisplayWebCam(PictureBox pic,int deviceno)
        {
            StartWebCam (pic.Height, pic.Width,(int) pic.Handle,deviceno );
        }


        public void StopWebCam(int deviceno)
        {
            SendMessage(deviceHandle, WM_CAP_DRIVER_DISCONNECT, deviceno , 0);
        }

    }
}

We have got a windows form Form1 in which there are two pictureboxes. On to display the live Web Camera, and the other to store a snap shot.

Here is Form1.cs

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 WebCamProject
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

             WebCamera.LoadAllDevices(lstDevices);
        }
        WebCamera d;
        private void button1_Click(object sender, EventArgs e)
        {
            if (lstDevices.SelectedIndex < 0)
            {
                MessageBox.Show(this, "Please select a device");
                return;
            }
            d =(WebCamera )lstDevices.SelectedItem;

            d.DisplayWebCam (picWebCam,lstDevices .SelectedIndex );
        }

        private void button2_Click(object sender, EventArgs e)
        {
            d.StopWebCam(lstDevices .SelectedIndex );
        }

        private void button3_Click(object sender, EventArgs e)
        {
            picSnap.Image = d.GetImage();
        }
    }
}

Form1.Designer.cs

namespace WebCamProject
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

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

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.button1 = new System.Windows.Forms.Button();
            this.lstDevices = new System.Windows.Forms.ListBox();
            this.picWebCam = new System.Windows.Forms.PictureBox();
            this.button2 = new System.Windows.Forms.Button();
            this.picSnap = new System.Windows.Forms.PictureBox();
            this.button3 = new System.Windows.Forms.Button();
            ((System.ComponentModel.ISupportInitialize)(this.picWebCam)).BeginInit();
            ((System.ComponentModel.ISupportInitialize)(this.picSnap)).BeginInit();
            this.SuspendLayout();
            //
            // button1
            //
            this.button1.Location = new System.Drawing.Point(71, 411);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(75, 23);
            this.button1.TabIndex = 0;
            this.button1.Text = "Start";
            this.button1.UseVisualStyleBackColor = true;
            this.button1.Click += new System.EventHandler(this.button1_Click);
            //
            // lstDevices
            //
            this.lstDevices.FormattingEnabled = true;
            this.lstDevices.Location = new System.Drawing.Point(12, 12);
            this.lstDevices.Name = "lstDevices";
            this.lstDevices.Size = new System.Drawing.Size(505, 173);
            this.lstDevices.TabIndex = 1;
            //
            // picWebCam
            //
            this.picWebCam.Location = new System.Drawing.Point(628, 28);
            this.picWebCam.Name = "picWebCam";
            this.picWebCam.Size = new System.Drawing.Size(359, 226);
            this.picWebCam.SizeMode = System.Windows.Forms.PictureBoxSizeMode.StretchImage;
            this.picWebCam.TabIndex = 2;
            this.picWebCam.TabStop = false;
            //
            // button2
            //
            this.button2.Location = new System.Drawing.Point(513, 411);
            this.button2.Name = "button2";
            this.button2.Size = new System.Drawing.Size(75, 23);
            this.button2.TabIndex = 3;
            this.button2.Text = "Stop";
            this.button2.UseVisualStyleBackColor = true;
            this.button2.Click += new System.EventHandler(this.button2_Click);
            //
            // picSnap
            //
            this.picSnap.Location = new System.Drawing.Point(628, 272);
            this.picSnap.Name = "picSnap";
            this.picSnap.Size = new System.Drawing.Size(359, 226);
            this.picSnap.SizeMode = System.Windows.Forms.PictureBoxSizeMode.StretchImage;
            this.picSnap.TabIndex = 2;
            this.picSnap.TabStop = false;
            //
            // button3
            //
            this.button3.Location = new System.Drawing.Point(234, 410);
            this.button3.Name = "button3";
            this.button3.Size = new System.Drawing.Size(135, 23);
            this.button3.TabIndex = 4;
            this.button3.Text = "Take Picture";
            this.button3.UseVisualStyleBackColor = true;
            this.button3.Click += new System.EventHandler(this.button3_Click);
            //
            // Form1
            //
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(1202, 522);
            this.Controls.Add(this.button3);
            this.Controls.Add(this.button2);
            this.Controls.Add(this.picSnap);
            this.Controls.Add(this.picWebCam);
            this.Controls.Add(this.lstDevices);
            this.Controls.Add(this.button1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            ((System.ComponentModel.ISupportInitialize)(this.picWebCam)).EndInit();
            ((System.ComponentModel.ISupportInitialize)(this.picSnap)).EndInit();
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.ListBox lstDevices;
        private System.Windows.Forms.PictureBox picWebCam;
        private System.Windows.Forms.Button button2;
        private System.Windows.Forms.PictureBox picSnap;
        private System.Windows.Forms.Button button3;
    }
}

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace WebCamProject
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}