cvLoadImage fail in ROS.

asked 2012-04-08 20:05:07 -0500

yclin
53 ●4 ●5 ●9

updated 2014-01-28 17:11:55 -0500

ngrennan
1 ●1 ●1

Hi Everyone: I tried to load a static image in ROS: here is the part of code: #include <highgui.h> #include <cv.h> using namespace std; using namespace cv;

       int main (int argc, char** argv) {
       ...........................
       if( ! cvLoadImage("13_45_07-65.bmp") ) cout << "sorry" << endl;
      ............................
       }

 in the log file, I can find a " sorry ", which means the image is not successfully loaded.

 the code works well outside ros. I put it in ROS because I need the images to tell when to send geometry_msg.

 I use ROS electric and configure OpenCV-2.3.1 according to http://www.ros.org/wiki/opencv2.  
 OpenCV is used with ROS as a rosdep system dependency      

 I put the followings in the CMakeLists.txt of the package the code is in.
 "  find_package(OpenCV REQUIRED)

if(OpenCV_FOUND) message("====== Found ${OpenCV_VERSION} =======") message("=== ${OpenCV_LIBS}======") endif(OpenCV_FOUND) "

the cmake .. returns: ====== Found 2.3.1 ======= === opencv_gpu;opencv_contrib;opencv_legacy;opencv_objdetect;opencv_calib3d;opencv_features2d;opencv_video;opencv_highgui;opencv_ml;opencv_imgproc;opencv_flann;opencv_core======

I have no idea why this simple OpenCV command in my code cannot be executed in ROS. Anyone can help me? Thank you in advance.

Yucong

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answered 2012-04-08 20:55:31 -0500

roehling
1951 ●25 ●28 ●43 http://www.fkie.fraunhofer.de/

The program is probably executed with a different working directory than you expect, so the image file cannot be found. AFAIK rosrun keeps the current working directory, while roslaunch changes to some entirely different place. Neither changes the working directory to the package directory.

Current best practice is to use the $(find foo) directive in the launch file to substitute the absolute path to the package foo in a configuration value.

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1

roslaunch is going (usually) going to run in ~/.ros, unless you change some environment variables.

Mac ( 2012-04-09 08:05:23 -0500 )edit

I think it does, but I have never read any official specification about that, so you probably should not rely on it.

roehling ( 2012-04-09 18:04:34 -0500 )edit

hello, I want to load one image in some folder (with cvLoadImage), What must I do to tell roslaunch to search in the correct folder? I try moving the image to ./ros and works very well but I want put in other folder. How?

pmarinplaza ( 2012-10-15 04:30:23 -0500 )edit

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answered 2012-04-09 22:21:52 -0500

Bence Magyar

358 ●8 ●12 ●23

updated 2012-04-11 03:03:09 -0500

I would vote for the includes, and the C-style function.

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

With these I'm not sure that you'll get what you need. The right way to do the includes is

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

Those includes above will reference to the old legacy versions of opencv still available in some Ubuntu versions.

Also if you are developing a new code (and I can see that it's C++) please use the new C++ API to easily avoid problems like memory leaks and such. Too bad that 95% of the example materials that can be found (official&unofficial) on OpenCV are still advertising the old API. For example your line of code would look like this:

if( cv::imread("13_45_07-65.bmp").empty() )
    cout << "sorry" << endl;

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Shouldn't this be 'if (cv::imread("13_45_07-65.bmp").empty())'? I am not sure what "!" does on cv::Mat...

Stephan ( 2012-04-10 01:00:43 -0500 )edit

fixed, thx

Bence Magyar ( 2012-04-11 00:41:49 -0500 )edit

...no... you should print "yeah" istead of "sorry" when image loading succeeds ;-)

Stephan ( 2012-04-11 00:56:15 -0500 )edit

:) modified it in a pessimist way

Bence Magyar ( 2012-04-11 03:03:55 -0500 )edit

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cvLoadImage fail in ROS.

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cvLoadImage fail in ROS.