Resizer for 9patch images based on im utils

9patch-resize.sh

#!/bin/bash
# resizer for android 9patch icons

# getting center part
convert -shave 1 $1 core.png

# getting sides
convert -gravity West -crop 1x+0+0 $1 l.png
convert -gravity East -crop 1x+0+0 $1 r.png
convert -gravity South -crop x1+0+0 $1 b.png
convert -gravity North -crop x1+0+0 $1 t.png

convert core.png -resize $2 -bordercolor transparent -border 1 core.png

w=`identify -format '%w' core.png`
h=`identify -format '%h' core.png`

composite -gravity East   \( r.png -filter Point -resize 1x${h}! \)  core.png  core.png
composite -gravity West   \( l.png -filter Point -resize 1x${h}! \)  core.png  core.png
composite -gravity South  \( b.png -filter Point -resize ${w}x1! \)  core.png  core.png
composite -gravity North  \( t.png -filter Point -resize ${w}x1! \)  core.png  out.png

rm l.png r.png b.png t.png core.png