Webcam face detection in C# using Emgu CV

March 22, 2009

Some time ago I wrote a post on how to do face detection in C# using OpenCV. I’ve since begun using the Emgu CV wrapper instead of opencvdotnet. Emgu CV is much better, in active development and it even runs on Mono. Two gotchas:

You don’t have to install OpenCV, but instead have to copy the relevant dlls (included with the Emgu CV download) to the folder where you code executes.
Open CV and X64 are not friends. If you’re running X64 Windows (and unless you are up to recompiling OpenCV) you have to make sure your app is compiled to X86, instead of the usual “Any CPU”.
Remember to add PictureBox as per the original tutorial.

Here’s sample code:

using System;
using System.Windows.Forms;
using System.Drawing;
using Emgu.CV;
using Emgu.Util;
using Emgu.CV.Structure;
using Emgu.CV.CvEnum;

namespace opencvtut
{
    public partial class Form1 : Form
    {
		private Capture cap;
		private HaarCascade haar;

        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
		using (Image<Bgr, byte> nextFrame = cap.QueryFrame())
		{
			if (nextFrame != null)
			{
				// there's only one channel (greyscale), hence the zero index
				//var faces = nextFrame.DetectHaarCascade(haar)[0];
				Image<Gray, byte> grayframe = nextFrame.Convert<Gray, byte>();
				var faces =
					grayframe.DetectHaarCascade(
						haar, 1.4, 4,
						HAAR_DETECTION_TYPE.DO_CANNY_PRUNING,
						new Size(nextFrame.Width/8, nextFrame.Height/8)
						)[0];

				foreach (var face in faces)
				{
					nextFrame.Draw(face.rect, new Bgr(0,double.MaxValue,0), 3);
				}
				pictureBox1.Image = nextFrame.ToBitmap();
			}
		}
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // passing 0 gets zeroth webcam
			cap = new Capture(0);
            // adjust path to find your xml
			haar = new HaarCascade(
                "..\\..\\..\\..\\lib\\haarcascade_frontalface_alt2.xml");
        }
    }
}

Comments

Stefan on May 10, 2009 at 6:20 pm

Thank you for that code.

Does anyone have some experience about training the HaarClassifier to create xml files for other objects…

Steven on May 13, 2009 at 8:48 am

Thanks, Sir. A question I want to consult you, how to access my webcam? When I run the code “cap = new Capture(0);” with my wired camera, there is no problem. However, I don’t know how to access my webcam. (I know the address of my webcam)

dee on June 26, 2009 at 3:43 pm

Have you tried running emgu on a shared hosting server that has trust=Medium forced? it doesn’t seem to like it at all.

friism on June 26, 2009 at 3:56 pm

@dee Yeah — that would make sense since EmguCV runs on top of OpenCV which is un-managed C++ code.

bijan on July 8, 2009 at 2:51 pm

hello sir
very good your document
tanks

bijan on July 8, 2009 at 2:52 pm

i’m iranian

Alex Park on July 29, 2009 at 11:46 am

I used this code to get Facedetection working in C#

however I have this problem when i complie.

It says that ‘var’ could not b found

and ‘Emgu.CV.HarrCascade’ does not contain a definition for ‘rect’

and ‘face’ cannot be declared in this scope becaue it would give a different meaning to ‘face, which is already used in a ‘parent or current’.

Lada on March 16, 2010 at 2:50 pm

I have this problem when i complie:
using (Image nextFrame = cap.QueryFrame())

Cannot convert type ‘Emgu.CV.Image’ to ‘System.Drawing.Image’

Thanks for help. Lada

Alex on April 20, 2010 at 8:59 pm

Thanks for posting your code. This is really helpful. For those getting the compile error, you’ll need to specify params to the Image object to ensure that it’s using Engu.CV.Image and not System.Drawing.Image:

using (Image nextFrame = cap.QueryFrame())
and
Image grayframe = nextFrame.Convert();

Alex on April 20, 2010 at 9:01 pm

Ah, I see that the blog software is stripping out the greater-than and less-than so my code snippets got edited. Let me try again:

using (Image<Bgr, Byte> nextFrame = cap.QueryFrame())

and

Image<Gray, Byte> grayframe = nextFrame.Convert<Gray, Byte>();

Komal on June 1, 2010 at 5:06 pm

Hi. When i run this code i get an exception at the line

Image grayframe = nextFrame.Convert();

and it says that this “conversion is not supported by OpenCV”
Now can anyone tel me how to solve it?

sonu on June 30, 2010 at 9:33 am

hiii
sir
can u suggest me how o train the databse on your own..
bcoz for side view the results are worst..
or if u could suggest me a way to detect side face of a human in the video with arnd 80 % accuracy..

sonu on July 16, 2010 at 3:57 am

sonu ->> http://note.sonots.com/SciSoftware/haartraining.html#t1a1f262

Can someone tell me how to extract the face detected and then do some extra detection ? I just need to get the face’s image croped in all frames…

thanks in advance

macias on September 26, 2010 at 7:04 pm

Thank you very very much for this entry. It really was super fast to get all the things working. Tested with VS2010, after hooking up the events, and enabling timer — just worked. You are the man, Michael!

Arpita Nagpal on October 6, 2010 at 1:13 pm

I used this code to get Facedetection and is working in C#.I used the web camera for this.
but what if i want to detect faces from a vedio?
at this line “capture = new Capture(0)”,instead of(0),i gave the path of the vedio file like”capture = new Capture(“path.avi”) but still its not working.

what should i do if i want to get faces from vedio instead of camera capture.

niko on October 11, 2010 at 10:58 am

it’s really 100% work’s…thank’s
just enable timer and change

using (Image nextFrame = cap.QueryFrame())

and

Image grayframe = nextFrame.Convert();

Fabio on October 20, 2010 at 3:50 pm

Great code.
How could I compare the face detected by the webcam with somekind of image database, to identify that ME is ME ? Got it?
Thanks.

friism on October 20, 2010 at 5:51 pm

@Fabio that problem is called face recognition: http://www.google.com/search?q=face+recognition

Ojulari Hakeem on October 31, 2010 at 11:04 pm

Emgu CV is just like a bomb. It actually works. U can use this code,

Image image = new Image(“DSC02624.jpg”); //Read the files as an 8-bit Bgr image
Image gray = image.Convert(); //Convert it to Grayscale

Stopwatch watch = Stopwatch.StartNew();
//normalizes brightness and increases contrast of the image
gray._EqualizeHist();

//Read the HaarCascade objects
HaarCascade face = new HaarCascade(“haarcascade_frontalface_alt_tree.xml”);
HaarCascade eye = new HaarCascade(“haarcascade_eye.xml”);

//Detect the faces from the gray scale image and store the locations as rectangle
//The first dimensional is the channel
//The second dimension is the index of the rectangle in the specific channel
MCvAvgComp[][] facesDetected = gray.DetectHaarCascade(
face,
1.1,
10,
Emgu.CV.CvEnum.HAAR_DETECTION_TYPE.DO_CANNY_PRUNING,
new Size(20, 20));

foreach (MCvAvgComp f in facesDetected[0])
{
//draw the face detected in the 0th (gray) channel with blue color
image.Draw(f.rect, new Bgr(Color.Blue), 2);

//Set the region of interest on the faces
gray.ROI = f.rect;
MCvAvgComp[][] eyesDetected = gray.DetectHaarCascade(
eye,
1.1,
10,
Emgu.CV.CvEnum.HAAR_DETECTION_TYPE.DO_CANNY_PRUNING,
new Size(20, 20));
gray.ROI = Rectangle.Empty;

foreach (MCvAvgComp e in eyesDetected[0])
{
Rectangle eyeRect = e.rect;
eyeRect.Offset(f.rect.X, f.rect.Y);
image.Draw(eyeRect, new Bgr(Color.Red), 2);
}
}

watch.Stop();
//display the image
ImageViewer.Show(image, String.Format(“Perform face and eye detection in {0} milliseconds”, watch.ElapsedMilliseconds));

Chris on November 19, 2010 at 4:43 am

I am having a problem with Capture();

I downloaded the Emgu sdk and ran (out of the box) some examples of webcam use, much like yours.. it worked fine.

I then did a rebuild all, and suddenly, I get this runtime error

The type initializer for ‘Emgu.CV.CvInvoke’ threw an exception.
“Unable to load DLL ‘cxcore210’: The specified module could not be found. (Exception from HRESULT: 0x8007007E)”}

THis happens on both VS2005 and VS2010

Any suggestions on how to fix this??

juhi on January 7, 2011 at 8:01 am

how to capture only the detected face and display in another picture box

juhi on January 7, 2011 at 11:07 am

reply fast…pleaseeeeeeeeeeeee….

Paul on January 15, 2011 at 11:34 pm

@ Chris
same here..
unable to load the dll.
I checked all locations and is where it should be, except VS2010 cant load it.

Johnykutty Mathew on January 29, 2011 at 7:09 pm

I experienced the same problem that Chris got
Anybody can give a solution??????????????
I am using emgucv 2.2 and vs2008

liudmi on February 15, 2011 at 11:23 pm

I used this code to get Facedetection working in C#

however I have this problem when i complie.

It says that ‘var’ could not b found

and ‘Emgu.CV.HarrCascade’ does not contain a definition for ‘rect’

and ‘face’ cannot be declared in this scope becaue it would give a different meaning to ‘face, which is already used in a ‘parent or current’.

Chaz Quire on March 1, 2011 at 1:00 pm

Hello,

I’m getting a NullReferenceException at:

using (Image nextFrame = cap.QueryFrame())

(I think that’s where it is where the problem occurs anyway)

Does anyone have any suggestions?

Thanks.
C.

jahangir on March 13, 2011 at 3:32 pm

its good.i am interested to recognized the facial expression

Kim Schulz on March 18, 2011 at 9:08 am

Hi,
I got this sample working with GTK# and it works pretty well. It does however use a lot of CPU. Any tricks on how to lower this without making the framerate too low?

kishan on March 21, 2011 at 12:57 pm

hey chris is got the same problem did you find any solution?

Taher on April 4, 2011 at 5:22 pm

@Chris: Just copy all the OpenCV dlls (including cxcore210) into your project folder. Also you must ensure that you are using EmguCV version <=2.1 since you are using OpenCV V2.1

Taher on April 4, 2011 at 5:24 pm

Guys this program works like a charm. Post your doubts, I might be able to help.

Lingaraj on May 6, 2011 at 1:08 pm

Excellent…

Sutirtha on November 30, 2011 at 10:24 pm

The code compiles fine but while running it throws an exception in the line :

using (Image nextFrame = cap.QueryFrame())

The Exception is : System.NullReferenceException

FYI…I am using laptop’s built in webcam.

Can someone please help on this.

kapil on February 26, 2012 at 12:19 pm

Error 1 The OutputPath property is not set for project ‘Emgu.CV.GPU.csproj’. Please check to make sure that you have specified a valid combination of Configuration and Platform for this project. Configuration=’Debug’ Platform=’MCD’. This error may also appear if some other project is trying to follow a project-to-project reference to this project, this project has been unloaded or is not included in the solution, and the referencing project does not build using the same or an equivalent Configuration or Platform. FaceDetection

Hi m trying to open facedetection example of emgu with my VS2010…but m getting the above error can anyone help please…..

sadany on April 8, 2012 at 1:20 am

can anyone help me and send me project face detection plzzzzzzzzzzzz @ [email protected]

MD. shifuddin al masud on July 12, 2012 at 5:47 pm

Thank you very much. Very good post….

paritosh on November 17, 2012 at 11:57 am

Can u pls help to tell me what I have to do for face detection on a uploaded image and not from web cam.

thank you

sandhya on May 13, 2013 at 3:42 am

hi, i am doing my final year BE project.In my project I wiil allow some fluid to flow through the catridge(box like material ). when the fluid reaches the end of catridge , i should detect th change.My program is to capture the images of the catridge from camera & crop the required part & then to compare the cropped image.I need to find the whether there is a change in the cropped part. I am using visual c# (windows form application) with opencvdotnet.Can any one help me.if u can then send me a [email protected]

My code is as below
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;
using System.Drawing.Imaging;
using OpenCVDotNet;
using System.IO.Ports;
using System.Threading;
namespace program
{
public partial class Form1 : Form
{
private CVCapture capture;
private CVImage backimage;
private bool first = false;

string pastimage, image;
int count = 0, count1 = 0;

public Form1()
{
InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)
{
timer1.Enabled = !(timer1.Enabled);
if (timer1.Enabled)
{
capture = new CVCapture(0);
}
else
{
capture.Release();
}
}

private void pictureBox1_Click(object sender, EventArgs e)
{

}

private void timer1_Tick(object sender, EventArgs e)
{
using (CVImage frame = capture.QueryFrame())
{
if (first == false)
{
backimage = frame;
first = true;
}

frame.Resize(320,240);
Bitmap new_frame = frame.ToBitmap();
Bitmap new_frame1;
Rectangle croprect3 = new Rectangle(30, 20, 47, 240);
new_frame.Save(@”C:\Documents and Settings\Administrator\Desktop\new\c.jpg”);
Bitmap target2 = new Bitmap(croprect3.Width, croprect3.Height);
using (Graphics g = Graphics.FromImage(target2))
{
g.DrawImage(new_frame, new Rectangle(0, 0, target2.Width, target2.Height), croprect3, GraphicsUnit.Pixel);
target2.Save(@”C:\Documents and Settings\Administrator\Desktop\new\c.jpg”, ImageFormat.Jpeg);
new_frame1 = target2;

}

pictureBox1.Image = frame.ToBitmap();
Bitmap new_backimage = backimage.ToBitmap();
Bitmap new_backimage1;

Rectangle croprect5 = new Rectangle(30, 20, 47, 240);
new_backimage.Save(@”C:\Documents and Settings\Administrator\Desktop\new \e.jpg”);
Bitmap target4 = new Bitmap(croprect5.Width, croprect5.Height);
using (Graphics g = Graphics.FromImage(target4))
{
g.DrawImage(new_backimage, new Rectangle(0, 0, target4.Width, target4.Height), croprect5, GraphicsUnit.Pixel);
target4.Save(@”C:\Documents and Settings\Administrator\Desktop\new \e.jpg”, ImageFormat.Jpeg);
new_backimage1 = target4;

}

if (new_frame1.Width == new_backimage1.Width && new_frame1.Height == new_backimage1.Height)
{

for (int r = 0; r < new_frame1.Width; r++)
{
for (int c = 0; c 15)
{

MessageBox.Show(“change found”);

}
else
{

MessageBox.Show(“change not found”);
}
//count1 = 0;
//count = 0;

}
}

}

else
{
MessageBox.Show(“Height and width don match”);
}

}
}
}
}

Arus on April 20, 2017 at 9:24 pm

Hey. I’m getting the [Cannot implicitly convert type ‘Emgu.CV.Image’ to ‘System.Drawing.Image’] error showing on this line in my code:

InputImage.Image = TestImage;

And it appears in the same line at 3 different places. Any help would be aprreciated

Michael Friis' Blog

Webcam face detection in C# using Emgu CV

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