trying to use imread() and imshow() raises OpenCV Error: Assertion failed (size.width>0 && size.height>0)

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 (!
        std::cout << "Image not loaded";
        return -1;

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

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