OpenCV tutorial Section 1.1, 1.2 - using notes

Now I am reading OpenCV tutorial section 1.1, 1.2 to learn how to 


1.1 Installation in Linux

...

Building OpenCV from source using CMake, using the command line

1. Create a temporary directory, which we denote as <cmake_binary_dir>, where you want to put the generated Makefiles, project files as well the object files and output binaries

2. Enter the <cmake_binary_dir> and type

cmake [<some optional parameters>] <path to the OpenCV source directory>

For example

cd ~/opencv

mkdir release

cd release

cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX= /usr/local

3. Enter the created temporary directory (<cmake_binary_dir>) and proceed with:

make

sudo make install


1.2 Using OpenCV with gcc and CMake

Steps

Create a program using OpenCV

Let’s use a simple program such as DisplayImage.cpp shown below.

#include <cv.h>

#include <highgui.h>

using namespace cv;

int main( int argc, char** argv )

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

Create a CMake file

Now you have to create your CMakeLists.txt file. It should look like this:

project( DisplayImage )

find_package( OpenCV REQUIRED )

add_executable( DisplayImage DisplayImage )

target_link_libraries( DisplayImage ${OpenCV_LIBS} )


Generate the executable

This part is easy, just proceed as with any other project using CMake:

cd <DisplayImage_directory>
cmake .
make

Result

By now you should have an executable (called DisplayImage in this case). You just have to run it giving an image
location as an argument, i.e.:

./DisplayImage lena.jpg

You should get a nice window as the one shown below.

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