Floating point exception when looping and reading images

asked 2017-03-14 02:39:33 -0500

bejazep gravatar image

updated 2017-03-14 02:43:16 -0500

I'm building a line following robot with OpenCV (c++), Raspberry Pi, Arduino, and an Arducam. I keep getting a Floating point exception when I decrease the delay time between image scans (at the end of the loop in main(), down to a 1 second delay). A bash script simultaneously captures an image from the Arducam, and the c++ program continuously reads the same image file name that's being written over.

At first I thought the exception was thrown because the image file was not finished being written to before it was read, but I wrote the loadImage() method in a way where (I hope) the method would not return until the data is complete. It could be wrong, I am just looking for a way to avoid or ignore the Floating point exception.

#include <iostream>
#include <string>
#include <opencv2/opencv.hpp>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/i2c-dev.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <iostream>

#define ADDRESS 0x04                        // The Arduino I2C address
static const char *devName = "/dev/i2c-1";  // The I2C bus

using namespace cv;
using namespace std;

// Line Detection program

// Efficient method to reduce noise
Mat& scanAndReduce(Mat& I, const int* const table)
    // accept only char type matrices
    CV_Assert(I.depth() == CV_8U);
    int channels = I.channels();
    int nRows = I.rows;
    int nCols = I.cols * channels;
    if (I.isContinuous())
        nCols *= nRows;
        nRows = 1;
    int i,j;
    uchar* p;
    for( i = 0; i < nRows; ++i)
        p = I.ptr<uchar>(i);
        for ( j = 0; j < nCols; ++j)
            p[j] = table[p[j]];
    return I;

// Loads command-line argument image file location
int loadImage(Mat& source, char argv[])
    while ( !source.data )
        source = imread(argv, 0);
    return 0;

// Displays input image in new window
void display(Mat& image)
    namedWindow("Result", WINDOW_NORMAL);
    imshow("Result", image);
// prints 10x10 ellipse with input center and height to input matrix
void drawEllipse(Mat& destination, int center, int lineY)
    ellipse( destination,                       // destination matrix
            Point(center,lineY),                // location
            Size(20,20),                        // size
            0,                                  // angle
            0,                                  // start
            360,                                // end
            Scalar(100,0,0));                   // color
// Scan bottom half of screen to see where line is
int scanLines(Mat& sourceImage)
    int diff = (sourceImage.rows) * 0.1;        // distance between scan lines
    int lineY = (sourceImage.rows) * 0.9;       // starting scan line
    int vals[sourceImage.cols];                 // save line values (left to right)
    int center = 0;                             // sums indexes of dark values
    int numDark = 0;                            // tracks dark values
    int offset = 0;

    // get values along scan lines
    for(int i = 0; i < 5; i++)                  // traverse y axis (bottom to top)
        center = 0;                             // sums indexes of dark values
        numDark = 0;                            // tracks dark values
        Scalar intensity;
        int leftBound = sourceImage.cols * 0.25;
        int rightBound = sourceImage.cols * 0.75;
        for(int j = leftBound; j < rightBound; j++) // traverse x axis of image
            intensity = sourceImage.at<uchar>(Point(j,lineY)); // save value
            vals[j] = intensity[0];             // get first value (greyscale)
            // save dark value
            if(vals[j] < 100)
                center += j;                    // add index to sum
                numDark++;                      // increment dark ...
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Why not pass the image (as an argument) to the c++ program that you call from the script?

boaz001 gravatar imageboaz001 ( 2017-03-14 09:19:18 -0500 )edit

Thanks for the suggestion! I tried it out and it's actually quite an improvement. I am still getting a floating point exception, but at least the program will continue running because the script keeps going. Now it seems like I am getting the exception becuase one of the image processing methods is not liking certain values. This also probably means that the image not being loaded is less of the problem, but this method is much better than before. I guess this problem is mostly solved now, since I have a way to ignore the error and just need to figure out how process the images correctly.

bejazep gravatar imagebejazep ( 2017-03-14 23:33:04 -0500 )edit

Yep, the scanLines() method is throwing the exception. I am not sure exactly why, but I needed to replace that method that has less issues overally anyways.

bejazep gravatar imagebejazep ( 2017-03-14 23:55:38 -0500 )edit