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"<=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 i…

Accepted Answer

`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
```

How to suppress OpenCV error message

Solution

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