How to preserve the original extension after multiple files manipulation

Question

This follow is a useful command to add a border to multiple images (require ImageMagick package): convert -border 5x5 -bordercolor "#008000" *.png imgs
The result is that the new files will be named something like imgs-0, imgs-1, imgs-2 ecc. I would like instead: imgs-0.png, imgs-1.png, imgs-2.png, or, even better, NEW*.png.

Answer 1

Use +adjoin and %d to write to multiple files with a more utile naming template:

 convert -border 5x5 -bordercolor "#008000" *.png +adjoin NEW_%d.png