This code plays sound of shapes

Makefile

all:
        g++ morph_descriptor.cpp -o MorphDescriptor -lao -lopencv_core -lopencv_highgui -lopencv_imgproc

morph_descriptor.cpp

#include <iostream>
#include <cmath>

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

#include <ao/ao.h>
#include <math.h>

#define BUF_SIZE 4096

void playBuffer(std::vector<float>& data)
{
    ao_device *device;
    ao_sample_format format;
    int default_driver;
    char *buffer;
    int buf_size;
    int sample;
    //float freq = 440.0;
    float freq = 220.0;
    int i;

    ao_initialize();

    default_driver = ao_default_driver_id();

    memset(&format, 0, sizeof(format));
    format.bits = 16;
    format.channels = 2;
    //format.rate = 44100;
    format.rate = 22050;
    format.byte_format = AO_FMT_LITTLE;

    /* -- Open driver -- */
    device = ao_open_live(default_driver, &format, NULL /* no options */);
    if (device == NULL) {
        fprintf(stderr, "Error opening device.\n");
        return;
    }

    /* -- Play some stuff -- */
    buf_size = format.bits/8 * format.channels * format.rate * 5;
    buffer = (char*)calloc(buf_size,
            sizeof(char));

    //for (i = 0; i < format.rate; i++)
    for (i = 0; i < buf_size; i++)
    {
        buffer[i] = data[i % data.size()];
    }
    ao_play(device, buffer, buf_size);

    /* -- Close and shutdown -- */
    ao_close(device);

    ao_shutdown();
}

float directionDistance(cv::Mat1b& img, cv::Point center, float angle)
{
    angle = (M_PI * angle) / 180;
    int x0 = center.x;
    int y0 = center.y;

    int x1 = center.x + 1000 * cos(angle);
    int y1 = center.y + 1000 * sin(angle);

    int dx = abs(x1-x0);
    int dy = abs(y1-y0);
    int sx = (x0 < x1) ? 1 : -1;
    int sy = (y0 < y1) ? 1 : -1;
    int err = dx-dy;

    cv::Point pt;    
    while(true)
    {
        pt = cv::Point(x0, y0);
        if((pt.x < img.cols) && (pt.y < img.rows) && (pt.x > 0) && (pt.y > 0))
        {
            uchar value = img.at<uchar>(pt);
            if(value == 0) { break; }
        }
        else { break; }

        if ((x0==x1) && (y0==y1)) { break; }
        int e2 = 2*err;
        if (e2 >-dy){ err -= dy; x0  += sx; }
        if (e2 < dx){ err += dx; y0  += sy; }
    }
    return cv::norm(center - pt);
}

void captureRadialFeatures(cv::Mat1b& img, float step, std::vector<float>& featureVec)
{
    cv::Moments m = cv::moments(img, true);
    cv::Point center(m.m10/m.m00, m.m01/m.m00);
    
    for(float i = 0; i < 360; i += step)
    {
        featureVec.push_back(directionDistance(img, center, i));
    }
}

int main(int argc, char** argv)
{
    if(argc < 2)
    {
        std::cout << "Usage: " << argv[0] << " <image_file>" << std::endl;
        return 0;
    }

    cv::Mat1b image = cv::imread(argv[1], 0);

    cv::Mat1b threshImg;
    cv::threshold(image, threshImg, 128, 255, cv::THRESH_BINARY_INV);
    cv::Mat1b auxImg;
    threshImg.copyTo(auxImg);

    std::vector<std::vector<cv::Point> > contours;
    std::vector<cv::Vec4i> hierarchy;
    cv::findContours(auxImg, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE);

    std::vector<cv::Rect> boundRect;

    cv::RNG rng(12345);
    cv::Mat drawing = cv::Mat::zeros(image.size(), CV_8UC3);
    for(int i = 0; i < contours.size(); i++)
    {
        cv::Scalar color = cv::Scalar(rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255));
        cv::drawContours(drawing, contours, i, color, 2, 8, hierarchy, 0);
        boundRect.push_back(cv::boundingRect(contours[i]));
        cv::rectangle(drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0);
    }

    cv::Mat drawingRoiImg(drawing, boundRect[0]);

    cv::Mat1b roiImg(threshImg, boundRect[0]);

    std::vector<float> featureVec;
    captureRadialFeatures(roiImg, 0.01, featureVec);
    playBuffer(featureVec);

    //for(int i = 0; i < featureVec.size(); i++)
    //{
    //    std::cout << featureVec[i] << std::endl;
    //}

    cv::imshow("DISPLAY", image);
    cv::imshow("DISPLAY_THRESH", threshImg);
    cv::imshow("DRAWING", drawing);
    cv::imshow("ROI", roiImg);
    cv::waitKey(0);
    
    return 0;
}