A brief introduction to OpenCV 2.3.1 for the Computer Vision Course at Politecnico di Torino (academic year 2011/2012).

1. Computer Vision
OpenCV
Luigi De Russis
Politecnico di Torino
Dipartimento di Automatica e Informatica (DAUIN)
Torino - Italy
luigi.derussis@polito.it
This work is licensed under the Creative Commons (CC BY-SA)
License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-sa/3.0/

2. What is OpenCV?
 Open source Computer Vision library
 Cross-platform
 C/C++ API
 Originally developed by Intel
 Optimized and intended for real-time applications
 More than 500 functions available
 Current release version: 2.3.1 (August 2011)
 Website: http://opencv.willowgarage.com/
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 2

3. Uses
 Human-Computer Interaction (HCI)
 Object Identification
 Object Recognition
 Face Recognition
 Gesture Recognition
 Motion Tracking
 Image Processing
 Mobile Robotics
 … and so on.
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 3

4. OpenCV modules (I)
 core
 basic structures and algorithms
 imgproc
 Image Processing algorithms (such as image filtering,
geometrical image transformations, histograms, etc.)
 highgui we will use Qt, in
 built-in simple UI addition to it
 video
 video analysis (such as motion estimation and object
tracking)
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 4

5. OpenCV modules (II)
 calib3d
 camera calibration and 3D reconstruction
 features2d
 2D features framework (feature detectors, descriptors,
and descriptor matchers)
 objdetect
 detection of objects and other items (e.g., faces, eyes,
mugs, people, …)
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 5

6. OpenCV modules (III)
 ml
 machine learning classes used for statistical
classification, regression and clustering of data
 gpu
 GPU-accelerated algorithms
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 6

7. cv::Mat
 cv
 all the OpenCV classes and functions are placed into
the cv namespace
 Mat
 the basic image structure in OpenCV
 overcomes the “old” IplImage problems
 automatic memory management (more or less)
 two data parts:
 matrix header (contains information about the matrix)
 a pointer to the matrix containing the pixel values
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 7

8. Demo Hour (I): Hello CV
 Goal: to load an image and show it
 Project available on the course page
 Two files:
 helloCV.pro
 main.cpp
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 8

9. Demo Hour (II)
 helloCV.pro, the Qt project file (the one to open!)
 to modify/copy on each new OpenCV+Qt project
 two important variables has to be defined:
INCLUDEPATH += path/to/opencv/include
LIBS += -Lpath/to/opencv/library
-lopencv_core231d
-lopencv_highgui231d
-lopencv_imgproc231d
…
-lopencv_video231d
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 9

10. Demo Hour (III)
 main.cpp, the code that loads and shows an image
…
//read an image
cv::Mat image = cv::imread("image.jpg");
//create an image window named "Hello CV“
cv::namedWindow("Hello CV");
//now, show the image on window
cv::imshow("Hello CV", image);
…
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 10

11. Demo Hour (IV)
 Now, press “Run”…
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 11

12. Resources
 OpenCV (Full) Wiki
http://opencv.willowgarage.com/wiki/FullOpenCVWiki
 OpenCV 2.3 Documentation http://opencv.itseez.com/
 [Book] Robert Laganière, OpenCV 2 Computer Vision Application
Programming Cookbook, Packt Publishing
 OpenCV User Group http://groups.yahoo.com/group/OpenCV/
 OpenCV 2.3 Tutorials
https://code.ros.org/trac/opencv/export/5642/trunk/opencv/doc/open
cv_tutorials.pdf
11/09/2011 Luigi De Russis - Computer Vision - OpenCV 12