Emgucv_Motion_Detection_MotionHistory_Human_Activity_in_video

This topic introduces you to the function MotionHistory of emgucv .


The motion history image (MHI) is a static image template helps in understanding the motion location and path as it progresses.


In MHI, the temporal motion information is collapsed into a single image template where intensity is a function of recency of motion.

The MHI pixel intensity is a function of the motion history at that location, where brighter values correspond to a more recent motion.


Using MHI, moving parts of a video sequence can be engraved with a single image, from where one can predict the motion flow as well as the moving parts of the video action.


Video  Effect 


Algorithm1

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for each time t
  Bt := absolute_difference(It, It-1) > threshold
end for

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Algorithm2

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for each time t
  for each pixel (x,y)
    if Bt(x,y) = 1
      MHIt(x,y) := τ
    else if MHIt-1 ≠ 0
      MHIt(x,y) := MHIt-1(x,y) - 1
    else
      MHIt(x,y) := 0
    end if
end for
=========================================================

If you want to know more information about

motion history

you can see this video

Video1





Video2_Image Moments








Video3_MHI




Code 

1. /*
2. * Copyright (c) 2016 Samuel <dryjoker007@gmail.com>
3. *
4. * BSD Simplified License.
5. * For information on usage and redistribution, and for a DISCLAIMER OF ALL
6. *
7. */
9. using System;
10. using System.Collections.Generic;
11. using System.ComponentModel;
12. using System.Data;
13. using System.Drawing;
14. using System.Linq;
15. using System.Text;
16. using System.Threading.Tasks;
17. using System.Windows.Forms;
18. using Emgu.CV;
19. using Emgu.CV.Util;
20. using Emgu.CV.Structure;
21. using Emgu.CV.VideoSurveillance;
22. using Emgu.CV.CvEnum;
25. namespace emgucv2._4._2_ex
26. {
28. public partial class Form1 : Form
29. {
30. private Capture _capture = new Capture();
31. private MotionHistory _motionHistory;
32. private IBGFGDetector<Bgr> _forgroundDetector;
33. public Form1()
34. {
35. InitializeComponent();
36. //try to create the capture
37. if (_capture == null)
38. {
39. try
40. {
41. _capture = new Capture();
42. }
43. catch (NullReferenceException excpt)
44. { //show errors if there is any
45. MessageBox.Show(excpt.Message);
46. }
47. }
48. if (_capture != null) //if camera capture has been successfully created
49. {
50. _motionHistory = new MotionHistory(
51. 1.0, //in second, the duration of motion history you wants to keep
52. 0.05, //in second, maxDelta for cvCalcMotionGradient
53. 0.5); //in second, minDelta for cvCalcMotionGradient
54. _capture.ImageGrabbed += ProcessFrame;
55. _capture.Start();
56. }
57. }
58. private void ProcessFrame(object sender, EventArgs e)
59. {
60. using (Image<Bgr, Byte> image = _capture.RetrieveBgrFrame())
61. using (MemStorage storage = new MemStorage()) //create storage for motion components
62. {
63. if (_forgroundDetector == null)
64. {
65. //_forgroundDetector = new BGCodeBookModel<Bgr>();
66. //_forgroundDetector = new FGDetector<Bgr>(Emgu.CV.CvEnum.FORGROUND_DETECTOR_TYPE.MOG);
67. _forgroundDetector = new BGStatModel<Bgr>(image, Emgu.CV.CvEnum.BG_STAT_TYPE.FGD_STAT_MODEL);
68. }
70. _forgroundDetector.Update(image);
72. capturedImageBox.Image = image.Bitmap;
74. //update the motion history
75. _motionHistory.Update(_forgroundDetector.ForgroundMask);
77. //forgroundImageBox.Image = _forgroundDetector.ForgroundMask.Bitmap;
79. #region get a copy of the motion mask and enhance its color
80. double[] minValues, maxValues;
81. Point[] minLoc, maxLoc;
82. _motionHistory.Mask.MinMax(out minValues, out maxValues, out minLoc, out maxLoc);
83. Image<Gray, Byte> motionMask = _motionHistory.Mask.Mul(255.0 / maxValues[0]);
84. #endregion
86. //create the motion image
87. Image<Bgr, Byte> motionImage = new Image<Bgr, byte>(motionMask.Size);
88. //display the motion pixels in blue (first channel)
89. motionImage[2] = motionMask;
91. //Threshold to define a motion area, reduce the value to detect smaller motion
92. double minArea = 150;
94. storage.Clear(); //clear the storage
95. Seq<MCvConnectedComp> motionComponents = _motionHistory.GetMotionComponents(storage);
97. //iterate through each of the motion component
98. foreach (MCvConnectedComp comp in motionComponents)
99. {
100. //reject the components that have small area;
101. if (comp.area < minArea) continue;
103. // find the angle and motion pixel count of the specific area
104. double angle, motionPixelCount;
105. _motionHistory.MotionInfo(comp.rect, out angle, out motionPixelCount);
107. //reject the area that contains too few motion
108. if (motionPixelCount < comp.area * 0.05) continue;
110. //Draw each individual motion in red
111. //DrawMotion(motionImage, comp.rect, angle, new Bgr(Color.Red));
112. }
114. // find and draw the overall motion angle
115. double overallAngle, overallMotionPixelCount;
116. _motionHistory.MotionInfo(motionMask.ROI, out overallAngle, out overallMotionPixelCount);
117. //DrawMotion(motionImage, motionMask.ROI, overallAngle, new Bgr(Color.Tomato));
119. //Display the amount of motions found on the current image
120. UpdateText(String.Format("Total Motions found: {0}; Motion Pixel count: {1}", motionComponents.Total, overallMotionPixelCount));
122. //Display the image of the motion
123. motionImageBox.Image = motionImage.Bitmap;
124. }
125. }
127. private void UpdateText(String text)
128. {
129. if (InvokeRequired && !IsDisposed)
130. {
131. Invoke((Action<String>)UpdateText, text);
132. }
133. else
134. {
135. label1.Text = text;
136. }
137. }
139. private static void DrawMotion(Image<Bgr, Byte> image, Rectangle motionRegion, double angle, Bgr color)
140. {
141. float circleRadius = (motionRegion.Width + motionRegion.Height) >> 2;
142. Point center = new Point(motionRegion.X + motionRegion.Width >> 1, motionRegion.Y + motionRegion.Height >> 1);
144. CircleF circle = new CircleF(
145. center,
146. circleRadius);
148. int xDirection = (int)(Math.Cos(angle * (Math.PI / 180.0)) * circleRadius);
149. int yDirection = (int)(Math.Sin(angle * (Math.PI / 180.0)) * circleRadius);
150. Point pointOnCircle = new Point(
151. center.X + xDirection,
152. center.Y - yDirection);
153. LineSegment2D line = new LineSegment2D(center, pointOnCircle);
155. image.Draw(circle, color, 1);
156. image.Draw(line, color, 2);
157. }
160. private void Form1_FormClosed(object sender, FormClosedEventArgs e)
161. {
162. _capture.Stop();
163. }
165. }
166. }