C++ OpenCV

OpenCV 3 Tutorial

image & video processing

OpenCV 3 image and video processing with Python

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In this chapter, I tried to install OpenCV on Windows 8 and Linux Fedora 18 using Visual Studio and Eclipse (Kepler/Juno). But not all of them was satisfactory, and got mixed results.

1. Visual studio 2012 - 32 bit OpenCV - OK
2. Visual studio 2012 - 64 bit OpenCV - Not tried
3. Eclipse Kepler (Windows 8) - 32 bit OpenCV with precompiled - Not satisfactory (needed some additional work)
4. Eclipse Kepler (Windows 8) - 32 bit OpenCV compiled with MinGW by myself - OK
5. Eclipse Kepler (Windows 8) - 64 bit OpenCV with MinGW64 - Not successful (I will try again later)
6. Eclipse Juno on Fedora 18 - 32 bit OpenCV - OK

Here are the steps to run the first OpenCV program on Windows 8 using Visual Studio 2012 (vc11).

1. Install OpevCV - C:\opencv
2. Setup the Windows environment
   
   1. Set Environment Variable : OPENCV_DIR = C:\OpneCV246\build\
   2. Set Path = %OPENCV_DIR%\x86\vc11\bin
3. Visual Studio setup
   
   1. Configuration Properties -> C/C++ -> General -> Additional Include Directories
      $(OPENCV_DIR)\include\opencv;$(OPENCV_DIR)\include
   2. Linker -> General -> Additional Library Directories
      $(OPENCV_DIR)\x86\vc11\lib
   3. Linker ->Input
      Put all the libraries from C:\opencv\build\x86\vc11\lib
      such as opencv_calib3d246.lib, opencv_calib3d246d.lib ...
4. Run the code shown below, then we'll have the picture on OpenCV window.
5. Note: I had several errors but most of them were related to some mistakes made during the steps listed here. So, if something wrong during the compile/run, we need to check if we got all the steps right rather than trying to fix obscure errors.
   I'll try x64 again later.

#include <cv.h>
#include <highgui.h>

int main()
{
          IplImage* img = cvLoadImage("C:/MyOpenCV/Images/MyPic.png");
          cvNamedWindow("MyOpenCV");
          cvShowImage("MyOpenCV", img);
          cvWaitKey(0);
          cvDestroyWindow("MyOpenCV");
          cvReleaseImage(&img;);
          return 0;
}

Compile and run, then we get the picture as below.

I had some issues on this. Probably related to 32/64. My Machine is x64 amd but I ended up using x86.

1. Install Eclipse Kepler.
2. CDT plugin
   1. Help->Install New Sofware...
   2. In Install popup, put this url : http://download.eclipse.org/tools/cdt/releases/kepler
      which we can get from http://www.eclipse.org/cdt/downloads.php.
   3. Click "Add...", then type in this tag: CDT_8_2_0
3. Install MinGW
   In my case, I put it under "eclipse" directory.
4. Install OpenCV2.4.6.
   1. Project Properties->C/C++ General->Paths and Symbols
   2. In Includes tab, add this: C:\opencv\build\include
   3. In Libraries tab, add this:
      libopencv_core246, libopencv_highgui246, libopencv_imgproc246
   4. In Library Paths tab, add this: C:\opencv\build\x86\mingw\lib
5. System Environment setting:
   C:\eclipse\MinGW\bin;C:\opencv\build\x86\mingw\bin;

The sample program looks like this:

#include <opencv/highgui.h>
#include <opencv/cv.h>
#include <iostream>

using namespace std;
using namespace cv;

int main( int argc, char** argv )
{

  Mat image;
  image = imread( argv[1], CV_LOAD_IMAGE_COLOR );

  if( argc != 2 || !image.data )
    {
      printf( "No image data \n" );
      return -1;
    }

  namedWindow( "Display Image", CV_WINDOW_AUTOSIZE );
  imshow( "Display Image", image );

  waitKey(0);

  return 0;
}

Build script:

13:31:57 **** Rebuild of configuration Debug for project DisplayImage ****
Info: Internal Builder is used for build
g++ "-IC:\\opencv\\build\\include" -O0 -g3 -Wall -c -fmessage-length=0 -o "src\\DisplayImage.o" "..\\src\\DisplayImage.cpp" 
g++ "-LC:\\opencv\\build\\x86\\mingw\\lib" -o DisplayImage.exe "src\\DisplayImage.o" -llibopencv_core246 -llibopencv_highgui246 -llibopencv_imgproc246 

13:32:01 Build Finished (took 4s.116ms)

Run it either from IDE or via prompt window using flower.png:

$ DisplayImage C:\TEST\flower.png

Note

1. Could not make 64bit working.
2. I needed some help to setup environment:
   1. Run mingw64env.cmd file whose contents looks like this:

      @title MinGW-w64 64-bit GCC build environment
      
      @echo Setting up environment for MinGW-w64 GCC 64-bit...
      
      @set PATH=%CD%\bin;%PATH%
      
      @call cmd
             

   2. After that, run the following command on the prompt window:

      gcc -Wl,--add-stdcall-alias -I"C:\Program Files\Java\jdk1.7.0_21\include" -shared -o macro_NativeMacropaco-PC.dll macro_NativeMacro.c -m64
            

Since I had numerous issues with pre-compiled version of OpenCV, in this section, I'll build it using CMake. The detailed process is well documented in stackoverflow.

1. Download and install MinGW and add to the system PATH with C:/eclipse/MinGW/bin
2. Download cmake from http://www.cmake.org and install it
3. Download OpenCV2.4.6 Windows version
4. Install/unzip Opencv to C:\OpenCV246\ (README,index.rst and CMakeLists.txt are there with all subfolders)
5. Run CMake GUI tool, then
6. Choose C:\OpenCV246\ as source
7. Choose the destination, C:\OpenCV246MinGW\x86 where to build the binaries
8. Press Configure button, choose MinGW Makefiles as the generator. There are some red highlights in the window, choose options as you need.
9. Press the Configure button again. Configuring is now done.
10. Press the Generate button.
    
    
    
11. Exit the program when the generating is done.
12. Exit the Cmake program.
13. Run the command line mode (cmd.exe) and go to the destination directory C:\OpenCV246MinGW\x86
14. Type mingw32-make. You will see a progress of building binaries. If the command is not found, you must make sure that the system PATH is added with C:/eclipse/MinGW/bin. The build continues according the chosen options to a completion.
15. Add the destination's bin directory, C:\OpenCV246MinGW\x86\bin, to System PATH
16. RESTART COMPUTER
17. Go to the Eclipse CDT IDE, create a C++ program using the sample OpenCV code.
18. Go to Project > Properties > C/C++ Build > Settings > GCC C++ Compiler > Includes, and add the source OpenCV folder C:\OpenCV246\build\include
19. Go to Project > Properties > C/C++ Build > Settings > MinGW C++ Linker > Libraries, and add to the Libraries (-l) one by one: opencv_calib3d246 opencv_contrib246 opencv_core246 opencv_features2d246 opencv_flann246 opencv_gpu246 opencv_highgui246 opencv_imgproc246 opencv_legacy246 opencv_ml246 opencv_nonfree246 opencv_objdetect246 opencv_photo246 opencv_stitching246 opencv_video246 opencv_videostab246
20. Add the built OpenCV library folder, C:\OpenCV246MinGW\x86\lib to Library search path (-L).

References on MinGW64: http://qt-project.org/wiki/MinGW-64-bit.

OpenCV install: we need to install opencv-devel as well.

1. opencv.x86_64 0:2.4.5-1.fc18: "sudo yum install opencv"
2. opencv-devel.x86_64 0:2.4.5-1.fc18: "sudo yum install opencv-devel"

Eclipse

1. Go to Project->Properties
2. In C/C++ Build, click on Settings. At the right, choose the Tool Settings Tab. Here we will enter the headers and libraries info:
   1. To find opencv files: type in "pkg-config --cflags opencv", then in my system, it is "-I/usr/include/opencv"
   2. In GCC C++ Compiler, go to Includes. In Include paths(-l) we should include the path of the folder where opencv was installed. In my system, this is /usr/include/opencv.
   3. Now go to GCC C++ Linker, there we have to fill two spaces:
      First in Library search path (-L) we have to write the path to where the opencv libraries reside, in my case the path is:
      

      /usr/lib64
      

      Then in Libraries(-l) add the OpenCV libraries that we may need. Usually just the 3 first on the list below are enough (for simple applications):
      opencv_core opencv_imgproc opencv_highgui opencv_ml opencv_video opencv_features2d opencv_calib3d opencv_objdetect opencv_contrib opencv_legacy opencv_flann

      To find out where the libs are:

      $ pkg-config --libs opencv
      -lopencv_calib3d -lopencv_contrib -lopencv_core -lopencv_features2d -lopencv_flann -lopencv_highgui -lopencv_imgproc -lopencv_legacy -lopencv_ml -lopencv_objdetect -lopencv_photo -lopencv_stitching -lopencv_superres -lopencv_ts -lopencv_video -lopencv_videostab  
      

   4. Hit OK.
3. Now, the project should be ready to be built. For this, go to Project->Build all.

This is based on Operations with images.

Load an image from a file:

Mat img = imread(filename, CV_LOAD_IMAGE_COLOR);

If you read a jpg (or png) file, a 3 channel image is created by default. If you need a grayscale image, use:

Mat img = imread(filename, CV_LOAD_IMAGE_GRAYSCALE);
...
namedWindow( "GrayscaleImage", CV_WINDOW_AUTOSIZE );
imshow( "GrayscaleImage", image );

More to come...