Declaration of function and use it

[jsulm]

@gauravsharma0190 Is ontrack.cpp part of your project and is it built?
"undefined reference to 'CannyThresold(int,void*)" - means linker cannot find CannyThresold(int,void*)

[gauravsharma0190]

@jsulm
Actually i put .h and .cpp file in my qt project folder.

[jsulm]

@gauravsharma0190 But did you add them to your project?
They should be in the PRO file, like:

SOURCES += main.cpp\
        mainwindow.cpp\
        ontrack.cpp

HEADERS  += mainwindow.h\
        ontrack.h

[gauravsharma0190]

@jsulm
i added it but gives error as
parse error onTrack.cpp
Makefile error 3

[jsulm]

@gauravsharma0190 After changing PRO file you need to rerun qmake (right-click on the project in QtCreator and then "Run qmake". Then do a rebuild.

[gauravsharma0190]

@jsulm
I done it
Now gives many error regarding onTrack.cpp file.

[jsulm]

@gauravsharma0190 Well, I guess you have many issues there...

[gauravsharma0190]

@jsulm
Yeap.
are they function's issuses or anything.
I can't undersatnd everything is all right so Why all these issuses are there.
I will send you these issue.

[gauravsharma0190]

@gauravsharma0190
Here are all the errors
...

/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:9: error: 'blur' was not declared in this scope
     blur(gray, edge, Size(3,3));
                               ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:6: error: 'Mat' does not name a type
 Mat image, gray, edge, cedge;
 ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:7: error: 'void CannyThreshold(int, void*)' was declared 'extern' and later 'static' [-fpermissive]
   static void CannyThreshold(int, void*)
                                        ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:-1: In function 'void CannyThreshold(int, void*)':

/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:9: error: 'edge' was not declared in this scope
     blur(gray, edge, Size(3,3));
                ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:9: error: 'edge' was not declared in this scope
     blur(gray, edge, Size(3,3));
                ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:9: error: 'blur' was not declared in this scope
     blur(gray, edge, Size(3,3));
                               ^

/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:12: error: 'Canny' was not declared in this scope
     Canny(edge, edge, edgeThresh, edgeThresh*3, 3);
                                                  ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:13: error: 'cedge' was not declared in this scope
     cedge = Scalar::all(0);
     ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:15: error: 'src' was not declared in this scope
     src.copyTo(cedge, edge);
     ^
/home/pi/Desktop/qt/Desktop1/onTrackBall.cpp:16: error: 'imshow' was not declared in this scope
     imshow("Edge map", cedge);
                             ^
/usr/local/include/opencv2/highgui/highgui.hpp:78: note:   'cv::imshow'
 CV_EXPORTS_W void imshow(const string& winname, InputArray mat);

[gauravsharma0190]

This post is deleted!

[gauravsharma0190]

@jsulm
Hey i have posted the error
i can't undersatnd why i am getting these error.
everything is all right.

[jsulm]

@gauravsharma0190 Nothing is all right with this code.
"was not declared in this scope" - you have to check where are those declared or why they are not declared (blur, edge, Mat,...). For example:

cedge = Scalar::all(0);

where is cedge declared? You're trying to access a variable which was not declared.

This one says that you first declared the function extern and later static. Why? Since it is just a function it neither has to be static nor extern!

error: 'void CannyThreshold(int, void*)' was declared 'extern' and later 'static' [-fpermissive]
   static void CannyThreshold(int, void*)

You really have to fix your code! And I really don't understand why you think your code is OK although there are really basic issues (not related to Qt at all)!

[gauravsharma0190]

@jsulm
i declare all these variable inside onTrach.cpp file.
blur is function name which is in imgproc.hpp header.
Canny is also function name which is declared in highgui.h header.

[jsulm]

@gauravsharma0190
Can you post onTrach.cpp and onTrach.h?

[gauravsharma0190]

@jsulm

#include"onTrack.h"
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/core/core.hpp>
#include<opencv2/imgproc/imgproc.hpp>
int edgeThresh = 1;
//Mat image,gray,edge,cedge; 

  void CannyThreshold(int, void*)
{
Mat image, gray, edge, cedge;
    blur(gray, edge, Size(3,3));

    // Run the edge detector on grayscale
    Canny(edge, edge, edgeThresh, edgeThresh*3, 3);
    cedge = Scalar::all(0);

    src.copyTo(cedge, edge);
    imshow("Edge map", cedge);
}

.H file

#define ONTRACKBALL_H_
  int CannyThreshold(int,void* );
#endif
//your code here

Mat is opencv function which is declare in highgui.h
header.
all these functions are present in header which i added in code.

[jsulm]

@gauravsharma0190 What is Mat and where is it declared?

[jsulm]

@gauravsharma0190 Didn't you forget

using namespace cv;

in the cpp file?

[gauravsharma0190]

@jsulm
Mat is basically a class with two data parts: the matrix header (containing information such as the size of the matrix, the method used for storing, at which address is the matrix stored, and so on) and a pointer to the matrix containing the pixel values (taking any dimensionality depending on the method chosen for storing) . The matrix header size is constant, however the size of the matrix itself may vary from image to image and usually is larger by orders of magnitude

[gauravsharma0190]

@gauravsharma0190
Hey jslum
thanks very mush i did it without error
Now new problem arises when i clicked the push button it tells
The program has unexpectedly finished.
/home/pi/Desktop/qt /build-Desktop1-GCC Local/Desktop crashed.

[jsulm]

@gauravsharma0190 Most probably it crashes because of an invalid pointer. Debug your application step by step to see where exactly it crashes.