OpenCV Error: Assertion failed (size.width>0 && size.height>0) simple code

This error means that you are trying to show an empty image. When you load the image with imshow, this is usually caused by:

1. The path of your image is wrong (in Windows escape twice directory delimiters, e.g. imread("C:\path\to\image.png") should be: imread("C:\\path\\to\\image.png"), or imread("C:/path/to/image.png"));
2. The image extension is wrong. (e.g. ".jpg" is different from ".jpeg");
3. You don't have the rights to access the folder.

A simple workaround to exclude other problems is to put the image in your project dir, and simply pass to imread the filename (imread("image.png")).

Remember to add waitKey();, otherwise you won't see anything.

You can check if an image has been loaded correctly like:

#include <opencv2\opencv.hpp>
#include <iostream>
using namespace cv;

int main()
{
    Mat3b img = imread("path_to_image");

    if (!img.data)
    {
        std::cout << "Image not loaded";
        return -1;
    }

    imshow("img", img);
    waitKey();
    return 0;
}

Usually it means that your image is not there, it's a basic assertion for checking if the content is displayable in the window before actually displaying it, and by the way you need to create a window in order to show the image namedWindow( "name") then imshow ("name", image);

I had the exact same problem, only in Raspbian. After hours of trying, the solution was pretty simple, I had to leave out the file extension.

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

using namespace std;
using namespace cv;
int main()
{
    Mat inputImage = imread("beniz1");
    imshow("Display Image", inputImage);
    waitKey(5000);

    return 0;
}