Generated MEX function from a custom C code, but gives empty output.

Hello, I’m trying to generate a MEX function based on the line segment detector (LSD) that is available in this repository: theWorldCreator/LSD: a Line Segment Detector (github.com). The function I’d like to convert looks like below:
double * lsd(int * n_out, double * img, int X, int Y);
Here are short descriptions for the input and output of the function:
n_out: Pointer to an int where LSD will store the number of line segments detected.
img: Pointer to input image data. It must be an array of doubles of size X x Y, and the pixel at coordinates (x,y) is obtained by img[x+y*X].
X: the number of columns of a given image
Y: the number of rows of a given image.
Returns: A double array of size 7 x n_out, containing the list of line segments detected.
The arguments n_out, X, and Y are needed to preallocate arrays in C, but we don’t necessarily need it when running it on MATLAB. Therefore, I created an entry point function that calls the LSD function but with img as an only input argument:
function out = m_lsd(img) %#codegen
% Entry point function

% Some parameters
n_out = int32(5000); % number of detected segments will be around 5000 at most.
imsize = int32(size(img));
X = imsize(1);
Y = imsize(2);

% Pre-allocate output array
out = coder.nullcopy(zeros(7, n_out));

% Generate C Code using existing C Code:
coder.updateBuildInfo(‘addSourceFiles’, ‘lsd.c’);
coder.updateBuildInfo(‘addIncludePaths’, ‘/path/to/my/folder’);
fprintf(‘Running LSD code written in C … nn’);
coder.ceval(‘lsd’, coder.ref(n_out), coder.ref(img), X, Y);

end
I also wrote a build function that looks like below:
function build(target)
% Entry-point function
entryPoint = ‘m_lsd’; % using a MATLAB function "m_lsd.m"

% Input is an array of type double with variable size
arg = coder.typeof(double(0), [Inf, Inf]);

% Configuration object
cfg = coder.config(target);

% Custom source files and source code
cfg.CustomSource = ‘lsd.c’;
cfg.CustomSourceCode = sprintf(‘%snr%snr%snr%snr%snr%s’, …
‘#include <stdio.h>’,…
‘#include <math.h>’,…
‘#include <limits.h>’,…
‘#include <float.h>’,…
‘#include "lsd.h"’);
% Generate and launch report
cfg.GenerateReport = true;
cfg.LaunchReport = false;

% Generate code
codegen(entryPoint, ‘-args’, {arg}, ‘-config’, cfg);

end
I built the mex function by running "build mex" and I got a MEX function without any error message. However, when I apply it to an example image, the MEX function only returns a zero matrix. Here is an example application of the mex function:
grayImg = double(imread(‘cameraman.tif’));
segs = m_lsd_mex(grayImg); % –> Gives a zero matrix, even though lsd.c returned meaningful reuslts
Could anyone advise me where I’m doing wrong? Thank you for your help…!Hello, I’m trying to generate a MEX function based on the line segment detector (LSD) that is available in this repository: theWorldCreator/LSD: a Line Segment Detector (github.com). The function I’d like to convert looks like below:
double * lsd(int * n_out, double * img, int X, int Y);
Here are short descriptions for the input and output of the function:
n_out: Pointer to an int where LSD will store the number of line segments detected.
img: Pointer to input image data. It must be an array of doubles of size X x Y, and the pixel at coordinates (x,y) is obtained by img[x+y*X].
X: the number of columns of a given image
Y: the number of rows of a given image.
Returns: A double array of size 7 x n_out, containing the list of line segments detected.
The arguments n_out, X, and Y are needed to preallocate arrays in C, but we don’t necessarily need it when running it on MATLAB. Therefore, I created an entry point function that calls the LSD function but with img as an only input argument:
function out = m_lsd(img) %#codegen
% Entry point function

% Some parameters
n_out = int32(5000); % number of detected segments will be around 5000 at most.
imsize = int32(size(img));
X = imsize(1);
Y = imsize(2);

% Pre-allocate output array
out = coder.nullcopy(zeros(7, n_out));

end
I also wrote a build function that looks like below:
function build(target)
% Entry-point function
entryPoint = ‘m_lsd’; % using a MATLAB function "m_lsd.m"

% Input is an array of type double with variable size
arg = coder.typeof(double(0), [Inf, Inf]);

% Configuration object
cfg = coder.config(target);

% Generate code
codegen(entryPoint, ‘-args’, {arg}, ‘-config’, cfg);

end
I built the mex function by running "build mex" and I got a MEX function without any error message. However, when I apply it to an example image, the MEX function only returns a zero matrix. Here is an example application of the mex function:
grayImg = double(imread(‘cameraman.tif’));
segs = m_lsd_mex(grayImg); % –> Gives a zero matrix, even though lsd.c returned meaningful reuslts
Could anyone advise me where I’m doing wrong? Thank you for your help…! Hello, I’m trying to generate a MEX function based on the line segment detector (LSD) that is available in this repository: theWorldCreator/LSD: a Line Segment Detector (github.com). The function I’d like to convert looks like below:
double * lsd(int * n_out, double * img, int X, int Y);
Here are short descriptions for the input and output of the function:
n_out: Pointer to an int where LSD will store the number of line segments detected.
img: Pointer to input image data. It must be an array of doubles of size X x Y, and the pixel at coordinates (x,y) is obtained by img[x+y*X].
X: the number of columns of a given image
Y: the number of rows of a given image.
Returns: A double array of size 7 x n_out, containing the list of line segments detected.
The arguments n_out, X, and Y are needed to preallocate arrays in C, but we don’t necessarily need it when running it on MATLAB. Therefore, I created an entry point function that calls the LSD function but with img as an only input argument:
function out = m_lsd(img) %#codegen
% Entry point function

% Some parameters
n_out = int32(5000); % number of detected segments will be around 5000 at most.
imsize = int32(size(img));
X = imsize(1);
Y = imsize(2);

% Pre-allocate output array
out = coder.nullcopy(zeros(7, n_out));

end
I also wrote a build function that looks like below:
function build(target)
% Entry-point function
entryPoint = ‘m_lsd’; % using a MATLAB function "m_lsd.m"

% Input is an array of type double with variable size
arg = coder.typeof(double(0), [Inf, Inf]);

% Configuration object
cfg = coder.config(target);

% Generate code
codegen(entryPoint, ‘-args’, {arg}, ‘-config’, cfg);

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