How to suppress OpenCV error message

Question

I am writing an OpenCV project using g++ and opencv 2.4.6

I have some code like this:

try 
{
    H = findHomography( obj, scene, CV_RANSAC );
}
catch (Exception &e)
{
    if (showOutput)
        cout<< "Error throwed when finding homography"<<endl;
    errorCount++;
    if (errorCount >=10)
    {
        errorCount = 0;
        selected_temp = -99;
        foundBB = false;
        bb_x1 = 0;
        bb_x2 = 0;
        bb_y1 = 0;
        bb_y2 = 0;
    }
    return -1;
}

Error will be thrown when the findHomography failed to find things. The error message includes:

OpenCV Error: Assertion failed (npoints >= 0 && points2.checkVector(2) 
== npoints && points1.type() == points2.type()) in findHomography, 
file /Users/dji-mini/Downloads/opencv- 2.4.6/modules/calib3d/src/fundam.cpp, 
line 1074
OpenCV Error: Assertion failed (count >= 4) in cvFindHomography, 
file /Users/dji-mini/Downloads/opencv-2.4.6/modules/calib3d/src/fundam.cpp, line 235

Since I know under what conditions the message would appear, I want to suppress these error messages. But I don't know how to do it.

In old version of OpenCV, there seems to have a "cvSetErrMode", which, according to other articles, is depreciated in OpenCV 2.X. So what function can I use to suppress OpenCV error messages?

Aurelius · Accepted Answer · 2013-07-10 16:06:17Z

18

cv::error() is called on every occurrence of an assertion failure. The default behavior is to print the assertion statement to std::cerr.

You can use the undocumented cv::redirectError() function to set a custom error-handling callback. This will override the default behavior of cv::error(). You first need to define a custom error-handling function:

int handleError( int status, const char* func_name,
            const char* err_msg, const char* file_name,
            int line, void* userdata )
{
    //Do nothing -- will suppress console output
    return 0;   //Return value is not used
}

And then set the callback before the code which throw:

    cv::redirectError(handleError);

try {
    // Etc...

If at any point you wish to restore the default behavior, you can do so:

cv::redirectError(nullptr);    //Restore default behavior; pass NULL if no C++11

answered Jul 10, 2013 at 16:06

Aurelius

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2 Comments

PaulYang Over a year ago

Thank you very much! It works very well. How did you find this function?

Albert Over a year ago

The function is documented now here and available as cvRedirectError. See also the related code of error() here. It will just call this instead of printing it to stderr, but it will still throw the exception.

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