How do I use SIFT in ROS project

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If you have a ROS project and you want to use SIFT algorithm, there is an implementation in OpenCV library.

If you choose the OpenCV 3, you will need to download an external modul opencv_contrib and give it as a flag to the cmake while installing the OpenCV 3 library. I haven't manage to make this solution work, since other packages in my project requested OpenCV 2.

I used OpenCV 2.4.8.

1. Download the source code
2. Make a new folder inside the OpenCV 2.4.8 folder. Name it 'build'
3. In console, go into 'build' folder and run following commands

Commands:

1. cmake -D CMAKE_INSTALL_PREFIX=/usr/include/ ..
2. make
3. sudo make install

the '/usr/include/' is the path where the OpenCV will be installed.

'..' tells the cmake where to find the source code for the OpenCV (that means one folder up).

When you have the OpenCV installed, you have to link it with your ROS project. In the 'CMakeLists.txt' of your project add following lines:

 find_package(OpenCV 2.4.8 EXACT REQUIRED)

 SET(OpenCV_LIBRARIES opencv_core opencv_highgui opencv_imgproc opencv_nonfree opencv_features2d)

 catkin_package(
 DEPENDS system_lib opencv2
 ...
 )

 include_directories(
 ${OpenCV_INCLUDE_DIRS}
 ...
 )

 target_link_libraries( ${PROJECT_NAME}_my_node ${catkin_LIBRARIES} ${OpenCV_LIBRARIES})

When you set 'OpenCV_LIBRARIES' you can only set those that you actually need. I left there all the other libraries because I think you will use then in your project anyway.

You have to include the header files into your project source file.

#include <opencv2/opencv.hpp>
#include <opencv2/nonfree/nonfree.hpp>

Now you can use one of the many examples to use SIFT in your project. For example here, here or here.