CurlyB's profile - activity

I'm using the OpenCV SURFDetector to search for keypoints in an image. In my program I want to give the user the opportunity to set the value of the minHessian with a trackbar, but this would mean that I would have to know the range of the hessian-values.

I know that the higher I set this threshold the less keypoints I get and vice versa.

Is there a way to calculate a range of the hessian values so I can set 0 (which would be a very high minHessian threshold) on my trackbar to “no keypoints” and 100 (which is probably minHessian=1 or 0) for “all possible keypoints”?

I've already asked this question on stackoverflow if you prefer answering there (or on both sides): http://stackoverflow.com/questions/22009556/opencv-surfdetector-range-of-minhessian

I've found my mistake. I accidentally copied the openCV-dlls of the VC12 folder, because I forgot that Visual Studio 2012 is VC11. Now it works. Maybe this will help someone else who has the same problem and copied the dlls of the wrong folder.

No, it still doesn't work, but thanks so far. Have you any other suggestions?

I've added the line assert(img.data), but the error stays the same.

I have this function in C++:

vector<KeyPoint> test(Mat img)
{
  int minHessian = 400;
  SurfFeatureDetector detector( minHessian );

  vector<KeyPoint> vKeypoints;
  detector.detect( img, vKeypoints );

  return vKeypoints;
}

When I call this function in my main-method everything works fine.

int main( int, char** argv )
{
    // path to a image-file
    char* input = "image.jpg";

    // read image into Mat img
    Mat img = imread( input, CV_LOAD_IMAGE_GRAYSCALE );

    // call function test
    test(img);

    waitKey(0);
    return 0;
}

But as soon as I'm calling this method twice...

int main( int, char** argv )
{
    // path to a image-file
    char* input = "image.jpg";

    // read image into Mat img
    Mat img = imread( input, CV_LOAD_IMAGE_GRAYSCALE );

    // call function test
    test(img);
    test(img); // <-- !!! second call

    waitKey(0);
    return 0;
}

...I get the following error:

Can anyone tell me where my mistake is and how I could fix this? I need to call this function twice with two different images, but every time I do this I get this error.

I'm using Visual Studio 2012.

I already asked this question on stackoverflow: http://stackoverflow.com/questions/21261709/debug-assertion-failed-expression-pfirstblock-phead-using-opencv-and-c-tr