I have to apologise for the bad image quality, I couldn’t printscreen and paste them in Photoshop

First off, select any image/graphic you’d like to test on. Preferably if it’s big enough so you’ll actually get to see the side borders. PLEASE TAKE NOTE!! Open up your image on a TRANSPARENT BACKGROUND!!

Open your image up in Photoshop and click on the Rectangular Marquee Tool.
The icon should look something like this >>

Use the Rectangular Marquee Tool and select the outer borders of the image, leaving enough spaces for the effect to show.. After you’ve done this, go to SELECT >> INVERSE.

Your image should look a little something, like this.

When you’re finished with selecting inverse, click on SELECT >> MODIFY >> SMOOTH. Set your sample radius to roughly 8px!

Make sure you’ve completed and followed all the steps above correctly, hit the DELETE button on your keyboard and this SHOULD be your final product

Please also remember to save your image on a .gif extension. The transparent background wouldn’t work in .jpeg formats!