Why this code returns Segmentation fault error?

I have implemented the following code to perform filter2D on a matrix. After I compiled the program it returns Segmentation fault error. In this program, I want to assign an input array in the program (don't want to load images). then perform a filter which is assigned inside the program to measure the time of the filter2D function for different matrices and kernels at runtime.

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
using namespace std;
using namespace cv;
int main(){ //Picture size for input and output are the same int Pxsize = 128; int Pysize = Pxsize; //Kernel size int Kxsize = 3; int Kysize = Kxsize; //filter arguments Point anchor; double delta; int ddepth; //name for out put char window_name[32] = "filter2D Demo"; Mat input[128][128]; Mat output[128][128]; Mat kernel[3][3]; // Initialize arguments for the filter anchor = Point( -1, -1 ); delta = 0; ddepth = -1; int i,j; //assign data between 0 and 255 to the input matrix for (i=0; i<Pxsize; i++) for (j=0; j<Pysize; j++) input[i][j]=(i*j)%255; //assign data to the kernel //assign data between 0 and 255 to the input matrix for (i=0; i<Kxsize; i++) for (j=0; j<Kysize; j++) kernel[i][j]=1; //the problem is here: filter2D((InputArray) input, (OutputArray) output, ddepth , ( InputArray) kernel, anchor, delta, BORDER_DEFAULT ); namedWindow( window_name, CV_WINDOW_AUTOSIZE ); imshow( window_name, (OutputArray) output ); return 0;
}

the output is:

Segmentation fault
------------------
(program exited with code: 139)
Press return to continue

I used this command for gcc 6.2.0 compiler in Linux mint

g++ -Wall -Wextra -Werror -pedantic -I/usr/local/include/opencv -I/usr/local/include/opencv2 -L/usr/local/lib/ -g -o "opencv" "opencv.cpp" -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_ml -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_objdetect -lopencv_contrib -lopencv_legacy -lopencv_stitching

Compilation finished successfully

Thanks in advance

1 Answer

According to the comments, the problem has been found! It is because of casting the Mat object to InputArray and OutputArray in filter2D function. I changed the implementation to the following program and it works.

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <time.h>
//Picture size for input and output are the same
#define MAX1 4096
#define Pxsize MAX1
#define Pysize Pxsize
//Kernel size
#define Kxsize 9
#define Kysize Kxsize
//number of iterations
#define NUM_LOOP 10000
using namespace std;
using namespace cv;
unsigned short int A[Pxsize][Pysize];
unsigned short int B[Pxsize][Pysize];
unsigned short int K[Kxsize][Kysize];
// measuring the time
double pTime = 0, mTime = 10; // to indicate how much program time is (pTime) and how much i want to wait (mTime)
struct timespec start;
int main(){ //singleCore struct timespec tStart, tEnd;//used to record the processiing time double tTotal , tBest=10000;//minimum of toltal time will asign to the best time int w=0; //filter arguments Point anchor; double delta; int ddepth; //assign data between 0 and 255 to the input matrix int i,j; for (i=0; i<Pxsize; i++) for (j=0; j<Pysize; j++) A[i][j] = (i+j)%255; //assign data to the kernel //assign data between 0 and 255 to the input matrix for (i=0; i<Kxsize; i++) for (j=0; j<Kysize; j++) K[i][j]=1; cv::Mat input = cv::Mat(Pxsize, Pysize, CV_8UC1, A); cv::Mat kernel = cv::Mat::ones(Kxsize, Kysize, CV_8UC1); //name for out put // Initialize arguments for the filter anchor = Point( -1, -1 ); delta = 0; ddepth = -1; do{// this loop repeat the body to record the best time clock_gettime(CLOCK_MONOTONIC,&tStart); //the problem is here: filter2D( input, output, ddepth , kernel, anchor, delta, 1 ); clock_gettime(CLOCK_MONOTONIC,&tEnd); tTotal = (tEnd.tv_sec - tStart.tv_sec); tTotal += (tEnd.tv_nsec - tStart.tv_nsec) / 1000000000.0; if(tTotal<tBest) tBest=tTotal; pTime += tTotal; } while(w++ < NUM_LOOP && pTime < mTime); //cout<<" "<< input<<endl; //cout<<" "<< output<<endl; printf("\nThe best time: %f sec in %d repetition for %dX%d matrix for %d, %d kernel \n",tBest,w, Pxsize, Pysize, Kxsize, Kysize); return 0;
}