I have noticed a strange feature while conducting some experiments. Look at the following. My large profile picture and small profile picture look different.
I can't believe that.
Why does this happen?
I uploaded this to change my profile picture. The result was interesting. The large profile picture was almost black, but the small was white. I thought that Codeforces uses Nearest-neighbor interpolation to scale pictures in proper sizes. (This is just a guess!)
Nearest-neighbor interpolation selects the value of nearest point and does not consider the values of neighboring points at all. I tracked which values are used and found how to make profile pictures look different.
So, how did you do it?
I used this python script to create a 3600x3600 image that will make your profile pictures look different. Requirements are Python 3 and PIL. First, save a 300x300 image that you would like you use as the large profile picture as
pic1.png. Likewise, save a 80x80 image for the sub profile picture as
pic2.png. Finally, run the script and upload
pic1.png will be the large profile picture, while
pic2.png being the small profile picture.
I hope you love this feature :D