[Qt-interest] Cannot call OpenCV 2.0 functions inside Qt slots

[Andres Sanin]

Hi all,

I have a Qt application that uses OpenCV for image processing.

Everything was working fine with OpenCV 1.0 but when I upgraded to
OpenCV 2.0 it started crashing.
I noticed that it only crashes whenever OpenCV functions are called
inside Qt slots.

For instance, the following slot:

void TestClass::on_testButton_clicked() {
   IplImage* src = cvLoadImage("test.jpg");
   IplImage* dst = cvCreateImage(cvGetSize(src), src->depth, src->nChannels);
   cvThreshold(src, dst, 100, 255, CV_THRESH_BINARY);
}

crashes when testButton is clicked.

However, if I call the same cvThreshold function in any other place,
such as inside the main() function
or inside the Widget constructor, it works fine. Also, if I put the
same code in a separate function and
call that function with QtConcurrent::run() inside the same slot, it
works fine too.

Why this behaviour? Are there any restrictions about the operations
that can be done inside Qt slots?

Thanks in advance,
Andres