Unspecified error (The function is not implemented.) - c++

Question

I want any advice how to solve this Error
I'm trying a sample code to check the opencv_contrib Extra modules using CMake
This is the error message:
And this is the sample code which I used
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace cv;
using namespace std;
Mat src; Mat src_gray;
int thresh = 100;
int max_thresh = 255;
RNG rng(12345);
/// Function header
void thresh_callback(int, void*);
/** #function main */
int main(int argc, char** argv)
{
/// Load source image and convert it to gray
src = imread("Baraya.jpg", 1);
/// Convert image to gray and blur it
cvtColor(src, src_gray, CV_BGR2GRAY);
blur(src_gray, src_gray, Size(3, 3));
/// Create Window
char* source_window = "Source";
namedWindow(source_window, CV_WINDOW_AUTOSIZE);
imshow(source_window, src);
createTrackbar(" Threshold:", "Source", &thresh, max_thresh, thresh_callback);
thresh_callback(0, 0);
waitKey(0);
return(0);
}
/** #function thresh_callback */
void thresh_callback(int, void*)
{
Mat threshold_output;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
/// Detect edges using Threshold
threshold(src_gray, threshold_output, thresh, 255, THRESH_BINARY);
/// Find contours
findContours(threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));
/// Approximate contours to polygons + get bounding rects and circles
vector<vector<Point> > contours_poly(contours.size());
vector<Rect> boundRect(contours.size());
vector<Point2f>center(contours.size());
vector<float>radius(contours.size());
for (int i = 0; i < contours.size(); i++)
{
approxPolyDP(Mat(contours[i]), contours_poly[i], 3, true);
boundRect[i] = boundingRect(Mat(contours_poly[i]));
minEnclosingCircle((Mat)contours_poly[i], center[i], radius[i]);
}
/// Draw polygonal contour + bonding rects + circles
Mat drawing = Mat::zeros(threshold_output.size(), CV_8UC3);
for (int i = 0; i< contours.size(); i++)
{
Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
drawContours(drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point());
rectangle(drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0);
circle(drawing, center[i], (int)radius[i], color, 2, 8, 0);
}
/// Show in a window
namedWindow("Contours", CV_WINDOW_AUTOSIZE);
imshow("Contours", drawing);
}

Answer 1

There is no error in the code you posted. It works well if you installed OpenCV properly. This error is because you didn't build with any windowing system .
This error is from here:
#if defined (HAVE_WIN32UI) // see window_w32.cpp
#elif defined (HAVE_GTK) // see window_gtk.cpp
#elif defined (HAVE_COCOA) // see window_carbon.cpp
#elif defined (HAVE_CARBON)
#elif defined (HAVE_QT) // see window_QT.cpp
#elif defined (WINRT) && !defined (WINRT_8_0) // see window_winrt.cpp
#else
// No windowing system present at compile time ;-(
//
// We will build place holders that don't break the API but give an error
// at runtime. This way people can choose to replace an installed HighGUI
// version with a more capable one without a need to recompile dependent
// applications or libraries.
void cv::setWindowTitle(const String&, const String&)
{
CV_Error(Error::StsNotImplemented, "The function is not implemented. "
"Rebuild the library with Windows, GTK+ 2.x or Carbon support. "
"If you are on Ubuntu or Debian, install libgtk2.0-dev and pkg-config, then re-run cmake or configure script");
}
So re-run CMAKE with WITH_WIN32UI, since you are on Windows, and eventually with WITH_QT.