Why does changing this picture in any way ruins the way it displays in unity?

Question

I downloaded a picture from a tutorial on how to create Flappy Bird in Unity: https://www.youtube.com/watch?v=ihvBiJ1oC9U

When I use it in Unity it works perfect however when I try to make any changes to it, whether by simple "Paint" or "Photoshop", the picture turns blurry and I can't understand why, here is a video where you can see the problem: https://i.sstatic.net/mke4V.jpg

Here are 2 of the picture's details page, on the left, the one I downloaded from the tutorial that works good, on the right the one I simply changed some pixels in "Paint": https://i.sstatic.net/YsLnF.jpg

Answer 1

Make sure you apply the right settings for your new image. Specifically the Alpha and Filter Mode.