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Getting NaN for image angle in emgucv with c#

I have referenced following link to develop following csharp code to detect angle of Image. https://stackoverflow.com/a/34285205/7805023
Image<Gray, byte> imgout = imgInput.Convert<Gray, byte>().Not().ThresholdBinary(new
Gray(50), new Gray(255));
VectorOfVectorOfPoint contours = new VectorOfVectorOfPoint();
Mat hier = new Mat();
CvInvoke.FindContours(imgout, contours, hier, Emgu.CV.CvEnum.RetrType.External, Emgu.CV.CvEnum.ChainApproxMethod.ChainApproxSimple);
for (int i = 0; i <= 1; i++)
{
Rectangle rect = CvInvoke.BoundingRectangle(contours[i]);
RotatedRect box = CvInvoke.MinAreaRect(contours[i]);
PointF[] Vertices = box.GetVertices();
PointF point = box.Center;
PointF edge1 = new PointF(Vertices[1].X - Vertices[0].X,
Vertices[1].Y - Vertices[0].Y);
PointF edge2 = new PointF(Vertices[2].X - Vertices[1].X,Vertices[2].Y - Vertices[1].Y);
double edge1Magnitude = Math.Sqrt(Math.Pow(edge1.X, 2) + Math.Pow(edge1.Y, 2));
double edge2Magnitude = Math.Sqrt(Math.Pow(edge2.X, 2) + Math.Pow(edge2.Y, 2));
PointF primaryEdge = edge1Magnitude > edge2Magnitude ? edge1 : edge2;
PointF reference = new PointF(Vertices[1].X, Vertices[0].Y);
double thetaRads = Math.Acos((primaryEdge.X * reference.X) + (primaryEdge.Y * reference.Y))/(edge1Magnitude* edge2Magnitude);
double thetaDeg = thetaRads * 180 / Math.PI;
}
I am getting NaN as output for angle. Please go through the code let me know what wrong I have done?
I have used emgucv for image processing.
Any help will be highly appreciated.

NaN, Not a Number, is returned by Math.Acos() when the provided value is not between -1 and 1.
Your calculation of thetaRads is wrong, you need to calculate the Acos of the vectors' dot product divided by the product of the vectors' magnitudes, as per:
double thetaRads = Math.Acos(((primaryEdge.X * reference.X) + (primaryEdge.Y * reference.Y)) / (primaryMagnitude * refMagnitude));

Logo recognition using emguCV

I have implemented this code and have detcted logo in couple of images,
I was able to get some results like this but I need to count that how many images contain this logo,
may be something like finding all keypoints of logo inside big image or some thing else.
I can see I have foud the logo inside big image but I want to confirm it programetically, using emguCV.
Please help.
-- edited
this is the piece of code with homography, can you guide me a bit here, because I am totaly new to emguCV and openV please help me counting these inlier
public static Mat Draw(Mat modelImage, Mat observedImage, out long matchTime)
{
Mat homography;
VectorOfKeyPoint modelKeyPoints;
VectorOfKeyPoint observedKeyPoints;
using (VectorOfVectorOfDMatch matches = new VectorOfVectorOfDMatch())
{
Mat mask;
FindMatch(modelImage, observedImage, out matchTime, out modelKeyPoints, out observedKeyPoints, matches,
out mask, out homography);
//Draw the matched keypoints
Mat result = new Mat();// new Size(400,400), modelImage.Depth, modelImage.NumberOfChannels);
Features2DToolbox.DrawMatches(modelImage, modelKeyPoints, observedImage, observedKeyPoints,
matches, result, new MCvScalar(255, 255, 255), new MCvScalar(255, 255, 255), mask);
#region draw the projected region on the image
if (homography != null)
{
//draw a rectangle along the projected model
Rectangle rect = new Rectangle(Point.Empty, modelImage.Size);
PointF[] pts = new PointF[]
{
new PointF(rect.Left, rect.Bottom),
new PointF(rect.Right, rect.Bottom),
new PointF(rect.Right, rect.Top),
new PointF(rect.Left, rect.Top)
};
pts = CvInvoke.PerspectiveTransform(pts, homography);
Point[] points = Array.ConvertAll<PointF, Point>(pts, Point.Round);
using (VectorOfPoint vp = new VectorOfPoint(points))
{
CvInvoke.Polylines(result, vp, true, new MCvScalar(255, 0, 0, 255), 5);
}
}
#endregion
return result;
}
}

I think my answer is a bit to late, but may I can help someone other. With following code snipppet you can count the matching feature points that belongs to you question (counting lines). The importents variables is the mask variable. It contains the informations.
private int CountHowManyParisExist(Mat mask) {
Matrix<Byte> matrix = new Matrix<Byte>(mask.Rows, mask.Cols);
mask.CopyTo(matrix);
var matched = matrix.ManagedArray;
var list = matched.OfType<byte>().ToList();
var count = list.Count(a => a.Equals(1));
return count;
}

EmguCV: Draw contour on object in Motion using Optical Flow?

I would like to do motion detection in C# (using EmguCV 3.0) to remove object in motion or in foreground to draw an overlay.
Here is a sample test I done with a Kinect (because It's a depth camera)
How can I get started with EmguCV 3.0 ?
I tried many background removal code that do not work
It seems OpticalFlow is a good start but there si no example in EmguCV 3.0
If I find the largest blob how can I find its contours ?
Can someone help me to get started ?
EDIT: 17/06/2015
In EmguCV3.0.0 RC I don't see OpticalFlow in the package and documentation:
http://www.emgu.com/wiki/files/3.0.0-rc1/document/html/b72c032d-59ae-c36f-5e00-12f8d621dfb8.htm
There is only : DenseOpticalFlow, OpticalFlowDualTVL1 ???
This is a AbsDiff Code:
var grayFrame = frame.Convert<Gray, Byte>();
var motionFrame = grayFrame.AbsDiff(backFrame)
.ThresholdBinary(new Gray(20), new Gray(255))
.Erode(2)
.Dilate(2);
Result:
I don't know how to get the motion in white ?
This is the Blob Code:
Image<Bgr, Byte> smoothedFrame = new Image<Bgr, byte>(frame.Size);
CvInvoke.GaussianBlur(frame, smoothedFrame, new Size(3, 3), 1); //filter out noises
Mat forgroundMask = new Mat();
fgDetector.Apply(smoothedFrame, forgroundMask);
CvBlobs blobs = new CvBlobs();
blobDetector.Detect(forgroundMask.ToImage<Gray, byte>(), blobs);
blobs.FilterByArea(400, int.MaxValue);
blobTracker.Update(blobs, 1.0, 0, 1);
foreach (var pair in blobs) {
CvBlob b = pair.Value;
CvInvoke.Rectangle(frame, b.BoundingBox, new MCvScalar(255.0, 255.0, 255.0), 2);
}
Result:
Why so much false positive ?
This is a MOG2 Code:
forgroundDetector.Apply(frame, forgroundMask);
motionHistory.Update(forgroundMask);
var motionMask = GetMotionMask();
Image<Bgr, Byte> motionImage = new Image<Bgr, byte>(motionMask.Size);
CvInvoke.InsertChannel(motionMask, motionImage, 0);
Rectangle[] rects;
using (VectorOfRect boundingRect = new VectorOfRect()) {
motionHistory.GetMotionComponents(segMask, boundingRect);
rects = boundingRect.ToArray();
}
foreach (Rectangle comp in rects) { ...
Result:
If I select the biggest Area how can I get the contour of the object ?

First, I can give you some example Optical Flow code.
Let oldImage and newImage be variables that hold the previous and current frame. In my code, it's of type Image<Gray, Byte>.
// prep containers for x and y vectors
Image<Gray, float> velx = new Image<Gray, float>(newImage.Size);
Image<Gray, float> vely = new Image<Gray, float>(newImage.Size);
// use the Horn and Schunck dense optical flow algorithm.
OpticalFlow.HS(oldImage, newImage, true, velx, vely, 0.1d, new MCvTermCriteria(100));
// color each pixel
Image<Hsv, Byte> coloredMotion = new Image<Hsv, Byte>(newImage.Size);
for (int i = 0; i < coloredMotion.Width; i++)
{
for (int j = 0; j < coloredMotion.Height; j++)
{
// Pull the relevant intensities from the velx and vely matrices
double velxHere = velx[j, i].Intensity;
double velyHere = vely[j, i].Intensity;
// Determine the color (i.e, the angle)
double degrees = Math.Atan(velyHere / velxHere) / Math.PI * 90 + 45;
if (velxHere < 0)
{
degrees += 90;
}
coloredMotion.Data[j, i, 0] = (Byte) degrees;
coloredMotion.Data[j, i, 1] = 255;
// Determine the intensity (i.e, the distance)
double intensity = Math.Sqrt(velxHere * velxHere + velyHere * velyHere) * 10;
coloredMotion.Data[j, i, 2] = (intensity > 255) ? 255 : intensity;
}
}
// coloredMotion is now an image that shows intensity of motion by lightness
// and direction by color.
Regarding the larger question of how to remove the foreground:
If I had a way to get a static background image, that's the best way to start. Then, the foreground would be detected by the AbsDiff method and using Erode and Dilate or Gaussian to smooth the image, then use blob detection.
For simple foreground detection, I found Optical Flow to be way too much processing (8fps max), whereas the AbsDiff method was just as accurate but had no effect on framerate.
Regarding contours, if you're merely looking to find the size, position, and other moments, then the blob detection in the AbsDiff tutorial above seems to be sufficient, which uses Image.FindContours(...).
If not, I would start looking at the CvBlobDetector class as used in this tutorial. There's a built-in DrawBlob function that might come in handy.

Emgu CV - How i can get all occurrence of pattern in Image

Hi have already function solution but one issue:
// The screenshot will be stored in this bitmap.
Bitmap capture = new Bitmap(rec.Width, rec.Height, PixelFormat.Format24bppRgb);
using (Graphics g = Graphics.FromImage(capture))
{
g.CopyFromScreen(rec.Location, new System.Drawing.Point(0, 0), rec.Size);
}
MCvSURFParams surfParam = new MCvSURFParams(500, false);
SURFDetector surfDetector = new SURFDetector(surfParam);
// Template image
Image<Gray, Byte> modelImage = new Image<Gray, byte>("template.jpg");
// Extract features from the object image
ImageFeature[] modelFeatures = surfDetector.DetectFeatures(modelImage, null);
// Prepare current frame
Image<Gray, Byte> observedImage = new Image<Gray, byte>(capture);
ImageFeature[] imageFeatures = surfDetector.DetectFeatures(observedImage, null);
// Create a SURF Tracker using k-d Tree
Features2DTracker tracker = new Features2DTracker(modelFeatures);
Features2DTracker.MatchedImageFeature[] matchedFeatures = tracker.MatchFeature(imageFeatures, 2);
matchedFeatures = Features2DTracker.VoteForUniqueness(matchedFeatures, 0.8);
matchedFeatures = Features2DTracker.VoteForSizeAndOrientation(matchedFeatures, 1.5, 20);
HomographyMatrix homography = Features2DTracker.GetHomographyMatrixFromMatchedFeatures(matchedFeatures);
// Merge the object image and the observed image into one image for display
Image<Gray, Byte> res = modelImage.ConcateVertical(observedImage);
#region draw lines between the matched features
foreach (Features2DTracker.MatchedImageFeature matchedFeature in matchedFeatures)
{
PointF p = matchedFeature.ObservedFeature.KeyPoint.Point;
p.Y += modelImage.Height;
res.Draw(new LineSegment2DF(matchedFeature.SimilarFeatures[0].Feature.KeyPoint.Point, p), new Gray(0), 1);
}
#endregion
#region draw the project region on the image
if (homography != null)
{
// draw a rectangle along the projected model
Rectangle rect = modelImage.ROI;
PointF[] pts = new PointF[] {
new PointF(rect.Left, rect.Bottom),
new PointF(rect.Right, rect.Bottom),
new PointF(rect.Right, rect.Top),
new PointF(rect.Left, rect.Top)
};
homography.ProjectPoints(pts);
for (int i = 0; i < pts.Length; i++)
pts[i].Y += modelImage.Height;
res.DrawPolyline(Array.ConvertAll<PointF, Point>(pts, Point.Round), true, new Gray(255.0), 2);
}
#endregion
pictureBoxScreen.Image = res.ToBitmap();
the result is:
And my problem is that, function homography.ProjectPoints(pts);
Get only first occurrence of pattern (white rectangle in pic above)
How i can Project all occurrence of template, respectively how I can get occurrence of template rectangle in image

I face a problem similar to yours in my master thesis. Basically you have two options:
Use a clustering such as Hierarchical k-means or a point density one such as DBSCAN (it depends on two parameters but you can make it threshold free in bidimensional R^2 space)
Use a multiple robust model fitting estimation techniques such as JLinkage. In this more advanced technique you clusters points that share an homography instead of cluster points that close to each other in euclidean space.
Once you partition your matches in "clusters" you can estimate homographies between matches belonging to correspondant clusters.

How to draw a dashed line over an object?

I am drawing a line on a control on my Windows form like this:
// Get Graphics object from chart
Graphics graph = e.ChartGraphics.Graphics;
PointF point1 = PointF.Empty;
PointF point2 = PointF.Empty;
// Set Maximum and minimum points
point1.X = -110;
point1.Y = -110;
point2.X = 122;
point2.Y = 122;
// Convert relative coordinates to absolute coordinates.
point1 = e.ChartGraphics.GetAbsolutePoint(point1);
point2 = e.ChartGraphics.GetAbsolutePoint(point2);
// Draw connection line
graph.DrawLine(new Pen(Color.Yellow, 3), point1, point2);
I would like to know if it is possible to draw a dashed (dotted) line instead of a regular solid line?

It's pretty simple once you figure out the formatting that defines the dashes:
float[] dashValues = { 5, 2, 15, 4 };
Pen blackPen = new Pen(Color.Black, 5);
blackPen.DashPattern = dashValues;
e.Graphics.DrawLine(blackPen, new Point(5, 5), new Point(405, 5));
The numbers in the float array represent dash lengths of different colors. So for a simple dash of 2 pixels on (black) and two off each your aray would look like: {2,2} The pattern then repeats. If you wanted 5-wide dashes with a space of 2 pixels you would use {5,2}
In your code it would look like:
// Get Graphics object from chart
Graphics graph = e.ChartGraphics.Graphics;
PointF point1 = PointF.Empty;
PointF point2 = PointF.Empty;
// Set Maximum and minimum points
point1.X = -110;
point1.Y = -110;
point2.X = 122;
point2.Y = 122;
// Convert relative coordinates to absolute coordinates.
point1 = e.ChartGraphics.GetAbsolutePoint(point1);
point2 = e.ChartGraphics.GetAbsolutePoint(point2);
// Draw (dashed) connection line
float[] dashValues = { 4, 2 };
Pen dashPen= new Pen(Color.Yellow, 3);
dashPen.DashPattern = dashValues;
graph.DrawLine(dashPen, point1, point2);

I think you can accomplish this by changing the pen you use to draw your line.
So, replace the last 2 lines in your example with:
var pen = new Pen(Color.Yellow, 3);
pen.DashStyle = DashStyle.Dash;
graph.DrawLine(pen, point1, point2);

Pen has a public property that is defined as
public DashStyle DashStyle { get; set; }
you can set DasStyle.Dash if you want to draw a Dashed line.

Pen.DashPattern will do this. Look here for an example

In more modern C#:
var dottedPen = new Pen(Color.Gray, width: 1) { DashPattern = new[] { 1f, 1f } };

To answer this question regarding the generation of a dashed line using the code-behind:
Pen dashPenTest = new(Brushes.DodgerBlue, 1);
Line testLine = new()
{
Stroke = dashPenTest.Brush, //Brushes.Aqua,
StrokeThickness = dashPenTest.Thickness,//1,
StrokeDashArray = new DoubleCollection() { 8,4 },
X1 = 0,
X2 = canvas.Width,
Y1 = 10,
Y2 = 10
};
canvas.Children.Add(testLine);
This answer make use of the generation of a canvas in the xaml:
<Canvas x:Name ="canvas" Background="White" Height="300" Width="300">
The important method here is the "StrokeDashArray" that generates the dashes for the line drawn. More information is given here: Shape.StrokeDashArray