Now the best way to preseerve image quality of the stock you're using is this (if you use photoshop I assume, otherwise feel free to ignore me)
>Open a new Project
>150x300 ofc
>Drag ur stock onto it
>Then Use Ctrl+T and hold shift to resize it to your liking (this step is not necessary unless the you drag the pic open in another project since the resizing option appears directy after you drag the pic to your empty canvas so just hold shift and re size it)
>Save your ava's in PNG format
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I made this, just a crop and added a border, no adjustments.