Call functions in other files in C++ and OpenCV - c++

Question

I know this might be a possible duplicate but I have actually gone through several posts on SO to try and solve this problem
I have the following code in OpenCV and C++
test.cpp
#include "opencv2/core/core_c.h"
#include "opencv2/core/core.hpp"
#include "opencv2/flann/miniflann.hpp"
#include "opencv2/imgproc/imgproc_c.h"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/video/video.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/objdetect/objdetect.hpp"
#include "opencv2/calib3d/calib3d.hpp"
#include "opencv2/ml/ml.hpp"
#include "opencv2/highgui/highgui_c.h"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/contrib/contrib.hpp"
#include <stdio.h>
#include <iostream>
#include <vector>
#include <math.h>
#include <string.h>
#include "draw_shapes.h"
using namespace cv;
using namespace std;
int main(){
Mat normal = imread("/INPUT 2.jpg");
Mat gray;
cvtColor(normal, gray,CV_RGB2GRAY);
Mat binary = gray > 128;
Point start = cv::Point(5.0,5.0);
Point end = cv::Point(200.0,200.0);
draw_line(binary, start, end, 0, 255, 0);
imshow("Draw_Line", binary);
while(waitKey(0)!=27){
;
}
return 0;
}
draw_shapes.cpp
#include "opencv2/core/core_c.h"
#include "opencv2/core/core.hpp"
#include "opencv2/flann/miniflann.hpp"
#include "opencv2/imgproc/imgproc_c.h"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/video/video.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/objdetect/objdetect.hpp"
#include "opencv2/calib3d/calib3d.hpp"
#include "opencv2/ml/ml.hpp"
#include "opencv2/highgui/highgui_c.h"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/contrib/contrib.hpp"
#include <stdio.h>
#include <iostream>
#include <vector>
#include <math.h>
#include <string.h>
#include "draw_shapes.h"
void draw_line(cv::Mat img, cv::Point start, cv::Point end, int B, int G, int R){
int thickness = 2;
int lineType = 8;
line(img,start,end,Scalar(B,G,R),thickness,lineType);
}
void draw_rectangle(cv::Mat img, cv::Point p1, cv::Point p2, int B, int G, int R){
int thickness = 2;
int lineType = 8;
rectangle(img, p1, p2, Scalar(B,G,R),thickness, lineType);
}
draw_shapes.h
#ifndef DRAWSHAPES_H
#define DRAWSHAPES_H
void draw_line(cv::Mat, cv::Point, cv::Point, int, int, int);
void draw_rectangle(cv::Mat, cv::Point, cv::Point, int, int, int);
#endif
compile_opencv.sh
#!/bin/bash
echo "compiling $1"
if [[ $1 == *.c ]]
then
gcc -ggdb `pkg-config --cflags opencv` -o `basename $1 .c` $1 `pkg-config --libs opencv`;
elif [[ $1 == *.cpp ]]
then
g++ -ggdb `pkg-config --cflags opencv` -o `basename $1 .cpp` $1 `pkg-config --libs opencv`;
else
echo "Please compile only .c or .cpp files"
fi
echo "Output file => ${1%.*}"
./${1%.*}
I have gone through almost every post on StackOverflow related to header files and including functions from external CPP files and this is what I got.
Now, when I compile, I get
undefined reference to 'draw_line(cv::Mat, cv::Point_<int>, cv::Point_<int>, int, int, int)'
I am taking a wild guess and saying that this might be because I am not compiling draw_shapes.cpp separately, but I tried a simple int add(int x, int y) in a C file and it worked directly. Where am I going wrong here?

Answer 1

(Based on Ben's comment)
This command should work:
g++ -ggdb `pkg-config --cflags opencv` test.cpp draw_shapes.cpp `pkg-config --libs opencv`
Note the backquotes around "pkg-config --cflags opencv" and "pkg-config --libs opencv". Reqular quotes ('), won't work - you really need backquotes here (`). The backquote key is just below the "Esc" key on most keyboards. Or just copy-paste them from your script.

Answer 2

Just as #Ben mentioned, You need to compile the draw_shapes.cpp file. The twist is, if You want to compile Your files separately You need to compile them as objects with -c switch, and then link them together. Further explanation in Your second thread