An unhandled exception of type 'System.NullReferenceExceptio

hi when you click on botton Recognize it display a error as follows: An unhandled exception of type 'System.NullReferenceException' occurred in CameraCapture.exe Additional information: Object reference not set to an instance of an object

in part: name = recognizer.Recognize (ExtFaces [faceNo]) ToString ().; stringOutput [faceNo] = name;

here is the link the code part:

private void RecognizeFaces()
{
//detect faces from the gray-scale image and store into an array of type 'var',i.e 'MCvAvgComp[]'

Image grayframe = GetGrayframe();

//Assign user-defined Values to parameter variables:
MinNeighbors = int.Parse(comboBoxMinNeigh.Text); // the 3rd parameter
WindowsSize = int.Parse(textBoxWinSiz.Text); // the 5th parameter
//ScaleIncreaseRate = Double.Parse(comboBoxScIncRte.Text); //the 2nd parameter

//for (int i = 0; i < NumNameLabels; i++)
//{
//NamePersons[i]=NameLabless[i]+"&"+IDLabless[i];
//}

var faces = grayframe.DetectHaarCascade(haar, ScaleIncreaseRate, MinNeighbors,
HAAR_DETECTION_TYPE.DO_CANNY_PRUNING,
new Size(WindowsSize, WindowsSize))[0];

if (faces.Length > 0)
{
Bitmap ExtractedFace; //empty
ExtFaces = new Image[faces.Length];

faceNo = 0;

foreach (var face in faces)
{
// ImageFrame.Draw(face.rect, new Bgr(Color.Green), 3);
t = t + 1;
//set the size of the empty box(ExtractedFace) which will later contain the detected face
ExtractedFace = new Bitmap(face.rect.Width, face.rect.Height);

ExtFaces[faceNo] = new Image(ExtractedFace);//= newExtractedImage;
ExtFaces[faceNo] = ExtFaces[faceNo].Resize(100, 100, Emgu.CV.CvEnum.INTER.CV_INTER_CUBIC);
//TermCriteria for face recognition with numbers of trained images like maxIteration
MCvTermCriteria termCrit = new MCvTermCriteria(ContTrain, 0.001);
if (trainingImages.ToArray().Length != 0)
{
//Eigen face recognizer
EigenObjectRecognizer recognizer = new EigenObjectRecognizer(
trainingImages.ToArray(),
NameLabless.ToArray(),
3000,
ref termCrit);

name = recognizer.Recognize(ExtFaces[faceNo]).ToString();
stringOutput[faceNo] = name;
}
faceNo++;
}

pbExtractedFaces.Image = ExtFaces[0].ToBitmap(); //draw the face detected in the 0th (gray) channel with blue color
t = 0;

if (stringOutput[0] == null)
{
label1.Text = "Unknown";
label9.Text = "";
}
//Draw the label for each face detected and recognized
else
{
//string[] label = stringOutput[faceNo].Split(',');
label1.Text = "Known";
// for (int i = 0; i < 2; i++)
//{
label9.Text = stringOutput[0];
//label7.Text = label[1];
//}
}
}
if (faceNo == 0)
{
MessageBox.Show("No face detected");
}
else
{
btnNextRec.Enabled = true;
btnPreviousRec.Enabled = true;
}
}

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Hemant Srivastava13y ago
My email ID is: [email protected]
khaledd khaledd13y ago
hello Hemant Srivastava please can you give me your E-mail for send my application and solve my problem after you return my application. because dificult for me to repair this application.
if there is no problem
Hemant Srivastava13y ago
Put some breakpoints in various place within your method. Then debug your code line by line by "step into" (F11 button). In this wa, you will figure it out from which line you are getting 'System.NullReferenceExceptio'.

Also keep all your funtinality within try-catch block.
Sunny Sharma13y ago
Hi Khaledd,

Since I'm not aware of the API you're using nor explained by you, I can't guess the fragment what is causing the Exception. Well, apart of this I don't see any try...catch block inside your code which I suggest you to surround your codes with to track it down where actually this null value is being assigned and why?

Hope it helps :)

Thanks.