How to fix OpenCV assertion failed error?

Question

When I try to run the code below in Visual Studio I getting an error message:

Unhandled exception at 0x00007FFC976DA839 in TestOpenCV.exe: Microsoft C++ exception: cv::Exception at memory location 0x0000003DAEEFF360.

And the command window show this message:

OpenCV(4.1.0-dev) Error: Assertion failed (size.width>0 && size.height>0) in cv::imshow, file C:\Users\hordon\opencv\modules\highgui\src\window.cpp, line 352

I can't figure out whats is wrong. My best guess is that I use a virtual Windows 10 on a Mac with Parallels Desktop and something is wrong with the path. But that would be strange since I copied the image directly next to the EXE. Any idea how to fix this?

#include "pch.h"
#include <iostream>
#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>

cv::Mat image;

void myMouseCallback(int event, int x, int y, int flags, void* userdata)
{
    if (flags & cv::MouseEventFlags::EVENT_FLAG_LBUTTON) {
        if (flags & cv::MouseEventFlags::EVENT_FLAG_SHIFTKEY) {
            cv::rectangle(image, { x,y }, { y, x }, CV_RGB(255, (x*y) % 255, (x + y) % 255));
        } else if (flags &cv::MouseEventFlags::EVENT_FLAG_ALTKEY) {
            cv::line(image, { x, y }, { y, x }, CV_RGB((y * x) % 255, (int)(sin((double)x / image.cols) * 255), (x * y * x - y) % 255));
        } else {
            cv::circle(image, { x,y }, (x + y) % 10, 0);
        }
    }

    cv::imshow("Ablak", image);
}

int main()
{
    image = cv::imread(".\\csillam.jpg");

    cv::Mat greyScale(image.rows, image.cols, CV_8UC1);
    for (int i = 0; i < greyScale.rows; ++i) {
        for (int j = 0; j < greyScale.cols; j++) {
            cv::Vec3b pixel = image.at<cv::Vec3b>(i, j);

            greyScale.at<uint8_t>(i, j) = (pixel[0] + pixel[1] + pixel[2]) / 3;
        }
    }
    cv::imshow("Greyscale", greyScale);

    cv::imshow("Ablak", image);
    cv::setMouseCallback("Ablak", myMouseCallback);

    cv::waitKey(0);
}

score 0 · Accepted Answer · answered Jun 19 '19 at 15:16

0

Check if the image was read correctly before further processing

image = cv::imread(".\\csillam.jpg");
if (!image.data)    // image was not created 
{
    exit(1);
}

answered Jun 19 '19 at 15:16

seccpur

4,996
2
13
21

Thank you! The problem was with the image, not with the code. From now I will check this first always. – Hordon Jun 19 '19 at 15:25

score 0 · Answer 2 · answered Jun 19 '19 at 15:27

0

But that would be strange since I copied the image directly next to the EXE

By default, Visual studio will set working directory elsewhere. You can find your current working directory or change it

answered Jun 19 '19 at 15:27

zteffi

660
5
18

How to fix OpenCV assertion failed error?

2 Answers2