Hi Guys,

I hope you can help me because I've tried everything and don't know what else to do. I keep getting the error "Object reference not set to an instance of an object" and I can't seem to figure out what the problem is. I've even tried instantiating the object and nothing seems to be working. Can anyone help me? The code is below. Thanks.

```
public virtual void Track(Bitmap bitmap, out Window targetRoi, out Window searchRoi, out Dictionary<string, string> information)
{
int MEANSHIFT_ITERATIONS = 30;
const int DISTANCE_ITERATIONS = 30;
float bhatCoeff1 = 0;
float bhatCoeff2 = 0;
int dIterations = 0;
int msIterations = 0;
float distance = 0;
Bitmap cropped = null;
int centreX = _targetRoi.CentreX; //ERROR
int centreY = _targetRoi.CentreY;
//Limit the iterations to a fixed number to avoid performance degradation
do
{
_searchRoi.EnsureLimits();
//Find candidate model at the region of interest
_histCand = _imgProc.Create1DHistogram(bitmap, _histTarget.BinCount1, _histTarget.BinCount2, _histTarget.BinCount3, _targetRoi.RegionOfInterest, _searchRoi.RegionOfInterest);
//Get BC
bhatCoeff1 = Metric.Evaluate(new BhattacharryyaCoefficient(_histTarget, _histCand));
//Calculate moments
cropped = GetImageSection(bitmap, _targetRoi);//crop the region of interest
_moment = new MSMoment(cropped, _histTarget, _histCand);
//Find the new centre
centreX = _targetRoi.RegionOfInterest.X + (int)(_moment.FirstMomentX / _moment.ZerothMoment);
centreY = _targetRoi.RegionOfInterest.Y + (int)(_moment.FirstMomentY / _moment.ZerothMoment);
//Move the roi & search window to the new centroid
_targetRoi.Offset(centreX - _targetRoi.CentreX, centreY - _targetRoi.CentreY);
_searchRoi.Offset(centreX - _searchRoi.CentreX, centreY - _searchRoi.CentreY);
//Find candidate model at the new location
_searchRoi.EnsureLimits();
_histCand = _imgProc.Create1DHistogram(bitmap, _histTarget.BinCount1, _histTarget.BinCount2, _histTarget.BinCount3, _targetRoi.RegionOfInterest, _searchRoi.RegionOfInterest);
//Get BC at the new location
bhatCoeff2 = Metric.Evaluate(new BhattacharryyaCoefficient(_histTarget, _histCand));
while ((bhatCoeff2 < bhatCoeff1) && (dIterations < DISTANCE_ITERATIONS))
{
centreX = (int)Math.Ceiling(((float)(centreX + _previousCentreX)) / 2);
centreY = (int)Math.Ceiling(((float)(centreY + _previousCentreY)) / 2);
//Move ROI to the new location
_targetRoi.Offset(centreX - _targetRoi.CentreX, centreY - _targetRoi.CentreY);
_searchRoi.Offset(centreX - _searchRoi.CentreX, centreY - _searchRoi.CentreY);
//Find candidate model at the new location
_searchRoi.EnsureLimits();
_histCand = _imgProc.Create1DHistogram(bitmap, _histTarget.BinCount1, _histTarget.BinCount2, _histTarget.BinCount3, _targetRoi.RegionOfInterest, _searchRoi.RegionOfInterest);
//Get BC at the new location
bhatCoeff2 = Metric.Evaluate(new BhattacharryyaCoefficient(_histTarget, _histCand));
dIterations++;
}
//Calculate the distance between two vectors
distance = (float)Math.Sqrt(Math.Pow((centreX - _previousCentreX), 2)
+ Math.Pow((centreY - _previousCentreY), 2));
_previousCentreX = centreX;
_previousCentreY = centreY;
msIterations++;
} while ((distance >= 0.1) && (msIterations < MEANSHIFT_ITERATIONS));
//save info
//_moment.Information.Clear();
_moment.Information.Add("Meanshift Iterations: ", msIterations.ToString());
_moment.Information.Add("Bhattacharyya Coeff: ", bhatCoeff2.ToString());
//check validity
if (centreX > 0 && centreY > 0)
{
//Move the roi & search window to the new centroid
_targetRoi.Offset(centreX - _targetRoi.CentreX, centreY - _targetRoi.CentreY);
_searchRoi.Offset(centreX - _searchRoi.CentreX, centreY - _searchRoi.CentreY);
_moment.Information.Add("Centroid: ", _targetRoi.CentreX.ToString() + ", " + _targetRoi.CentreY.ToString());
//_processedImage = Drawer.DrawMoment(bitmap, _moment, new Point(centreX, centreY));
_processedImage = Drawer.DrawWindow(bitmap, _targetRoi, Color.Red);
_processedImage = Drawer.DrawWindow(bitmap, _searchRoi, Color.Yellow);
}
//save ROIs for next frame
targetRoi = _targetRoi;
searchRoi = _searchRoi;
information = _moment.Information;
}
```