Add pixels to an existing texture inside blender For example.
I have image 500x500 px

Can I change it to 520x520px in blender?
Those additional pixels can be white, black or transparent.

It's quite easy in photoshop or something similar but I would like to do this in blender.

Or maybe if I have 500x500 px image I could create a new texture in blender. Size 520x520 and then copy and paste original texture on top of it.

(I have image that I'll use as a factor in mix nodes. It has sharp edges and I would like to add 20 pixels around and soften the border. That's why I want to resize image)
With Compositor window: here is an example of a 1024*1024 image as backplate of a 500*500 image, that you can save as image, even without rendering.