Octave to C bridging for calling an Octave / MatLAB routine from a C program

extlibrary.cpp

// clear; mkoctfile extlibrary.cpp -o extlibrary.a


// mkoctfile extlibrary.cpp -M --link-stand-alone -o extlibrary.a
// clear; mkoctfile extlibrary.cpp --link-stand-alone -o extlibrary.o

//#include <iostream>

#include <octave-3.2.4/octave/oct.h>
#include <octave-3.2.4/octave/octave.h>
#include <octave-3.2.4/octave/parse.h>
#include <octave-3.2.4/octave/toplev.h>

#include "extlibrary.h"

#include <opencv2/opencv.hpp>

//using namespace std;
using namespace cv;

//int main (void) {
//	cout << "Hello Octave world!\n";
//	int n = 2;
//	Matrix a_matrix = Matrix (n, n);
//	for (octave_idx_type i = 0; i < n; i++)
//	{
//		for (octave_idx_type j = 0; j < n; j++)
//		{
//			a_matrix (i, j) = (i + 1) * 10 + (j + 1);
//		}
//	}
//	cout << a_matrix;
//	return 0;
//}

Mat extfunction(Mat input) {
	
	string_vector argv (2);
	argv(0) = "embedded";
	argv(1) = "-q";
	
	octave_main (2, argv.c_str_vec(), 1);
	
	octave_idx_type m = input.rows;
	octave_idx_type n = input.cols;
	Matrix a_matrix = Matrix (n, m);
	
//	cout << "X of [";
	for (octave_idx_type i = 0; i < n; i++) {
		for (octave_idx_type j = 0; j < m; j++) {
			a_matrix(i,j) = input.at<float>(i,j);
//			cout<< a_matrix(i,j);
//			if ( j != m - 1 ) {
//				cout<<", ";
//			} else {
//				cout<<"]";
//				if( i != n - 1 ) {
//					cout<<", "<<endl;
//				} else {
//					cout<<" ";
//				}
//			}
		}
	}
//	cout << "] is ";
	
	octave_value_list in = octave_value (a_matrix);
	octave_value_list out = feval ("getIdentity", in, 1);
	
//	return Mat();
	
	if (!error_state && out.length() > 0) {
		
		a_matrix = out(0).matrix_value();
		
		//		if (a_matrix.numel () == 1) {
		//			cout << a_matrix(0) << "\n";
		//		} else {
		//			cout << "invalid\n";
		//		}
		
		Mat ris = Mat::zeros(input.rows,input.cols,CV_32FC1);
		for(int i=0; i<a_matrix.rows(); i++) {
			for(int j=0; j<a_matrix.cols(); j++) {
				ris.at<float>(i,j) = a_matrix(i,j);
			}
		}
		
//		cout<<ris<<endl;
		return ris;
		
	} else {
		
//		cout<<"invalid\n";
		return Mat();
		
	}
	
}

double** extfunction(double* input, int input_m, int input_n) {
	
	string_vector argv (2);
	argv(0) = "embedded";
	argv(1) = "-q";
	
	octave_main (2, argv.c_str_vec(), 1);
	
	octave_idx_type m = input_m;
	octave_idx_type n = input_n;
	Matrix a_matrix = Matrix (n, m);
	
//	std::cout << "X of [";
	for (octave_idx_type i = 0; i < n; i++) {
		for (octave_idx_type j = 0; j < m; j++) {
			a_matrix(i,j) = input[ j + i * m ];
//			std::cout<< input[ j + i * m ];
//			if ( j != m - 1 ) {
//				std::cout<<", ";
//			} else {
//				std::cout<<"]";
//				if( i != n - 1 ) {
//					std::cout<<", "<<std::endl;
//				} else {
//					std::cout<<" ";
//				}
//			}
		}
	}
//	std::cout << "] is ";
	
	octave_value_list in = octave_value (a_matrix);
	octave_value_list out = feval ("getIdentity", in, 1);
	
	if (!error_state && out.length() > 0) {
		
		a_matrix = out(0).matrix_value();
		
//		if (a_matrix.numel () == 1) {
//			cout << a_matrix(0) << "\n";
//		} else {
//			cout << "invalid\n";
//		}
		
		double ** ris = new double*[a_matrix.rows()];
		for(int i=0; i<a_matrix.rows(); i++) {
			ris[i] = new double[a_matrix.cols()];
			for(int j=0; j<a_matrix.cols(); j++) {
				ris[i][j] = a_matrix(i,j);
			}
		}
		return ris;
	} else {
//		std::cout<<"invalid\n";
		return 0;
	}
	
}

extlibrary.h

#include <opencv2/opencv.hpp>

cv::Mat extfunction(cv::Mat input);

double** extfunction(double* input, int input_m, int input_n);

getIdentity.m

function ris = getIdentity(a)

[m n] = size(a);

ris = eye(max([m n]));

end

octave2c_bridge.c

//
//  main.cpp
//  testMathlab
//
//  Created by Fabio Cigliano on 23/08/13.
//  Copyright (c) 2013 Fabio Cigliano. All rights reserved.
//
// http://www.mathworks.it/it/help/matlab/calling-matlab-engine-from-c-c-and-fortran-programs.html
// http://www.mathworks.it/videos/generating-c-code-from-matlab-code-68964.html
// http://www.gnu.org/software/octave/doc/interpreter/Standalone-Programs.html#Standalone-Programs
// http://octave.1599824.n4.nabble.com/Calling-Octave-Function-from-Xcode-Program-td4654943.html
// mkoctfile --link-stand-alone main.cpp -o main
// http://stackoverflow.com/questions/9410328/how-to-call-a-matlab-code-from-objective-c
// http://octave.1599824.n4.nabble.com/Matlab-vs-Octave-td2275851.html
// Currently, there is no Octave compiler. Octave is a pure interpreter.
// http://www.mathworks.it/products/compiler/
// http://www.mathworks.com/matlabcentral/fileexchange/12987
// http://www.mathworks.it/it/help/matlab/programming-interfaces-for-c-c-fortran-com.htmls

#include <iostream>
#include <opencv2/opencv.hpp>

#include "extlibrary.h"

using namespace std;
using namespace cv;

int main (void) {
	
//	double input[2] = { 0 , 1 };
//	
//	cout<<"calling extfunction"<<endl<<endl;
//	
//	double** ris;
//	
//	ris = extfunction(input,2,1);
//	
//	cout<<endl<<"result: "<<ris<<endl;
//	for(int i=0;i<2;i++) {
//		for(int j=0;j<2;j++) {
//			cout<<ris[i][j]<<" ";
//		}
//		cout<<endl;
//	}
	
	Mat in = Mat::zeros(10,10,CV_8UC1);
	
	cout<<"input: "<<in<<endl;
	
	cout<<"calling extfunction"<<endl<<endl;
	
	Mat out = extfunction(in);
	
	cout<<endl<<"result: "<<out<<endl;
	
	return 0;
}