In the CTF we were given two images. As the description said ''Look sharp and compare the two images!''. So basically by having image 1 - and image 2 -, I decided to go with the terminal in Linux to find the hidden flag but I didn't use the terminal properly and it resulted in googling for simple image comparer online - . By uploading the two images and putting the result in a third one, you can see the flag in the processed image with the difference - pactf{c4rrots_are_good_4_eyesight}

Also there was a suggestion using ImageMagick by the syntax - compare image1 image2 -compose src diff.png