This documentation explains how an external Image can be tested and compared with the output image of OpenCV. For example, To compare two blurred images and test if they both are same, we blur an original image in an external software (I used WiT Image Processing software) or just download any blurred image online- output1. Create a Win32 OpenCV project in Visual Studio. Read the original image as an input to the OpenCV. Blur the original image in OpenCV and compare with output1.