It requires some small margin of white pixels around the logo to enable antialiasing around the edge of the logo.
You can make one form a 48x48 transparent logo with
```
-convert jalview_logo-48.png -gravity center -background white -extent 60x60 rotatable_jalview_logo-48.png
+convert jalview_logo-38.png -gravity center -background white -extent 60x60 rotatable_jalview_logo-38.png
```