Resize icon using imagemagick or ffmpeg

iconresize.sh

#!/usr/bin/env bash

# 
# Install:
#   cp iconresize.sh ~/bin/iconresize
#   chmod 0700 ~/bin/iconresize
#
# How to use:
#   iconresize <filename:icon.png> <directory:android> <tool:im|ff>
#
# Where:
#   im means ImageMagick (default)
#   ff means ffmpeg
#
# Example:
#   iconresize icon.png zabbix 
# 
__imgSource=${1:-icon.png}
__imgDest=${__imgSource%.*}
__imgRepository=${2:-Icons}
__imgTool=${3:-im}

# 
[ -f ${__imgSource} ] ||  exit 0
[ -d ${__imgRepository} ] || mkdir -p ${__imgRepository}

__imgSizes=(
   "24x1" "48x1" "64x1" "96x1" "128x1" 
   "20x1" "20x2" "20x3" 
   "29x1" "29x2" "29x3" 
   "40x1" "40x2" "40x3" 
   "60x2" "60x3" 
   "76x1" "76x2" 
   "83.5x2" "1024x1"
)

# resizing
for eSize in ${__imgSizes[*]}; do
   size=${eSize%x*}
   scale=${eSize##*x}
   resize=$((${size}*${scale}))
   echo "resizing ${__imgSource} to ${size}x${size}@${scale}"
   if [[ "${__imgTool}" == "ff" ]]; then
      ffmpeg -loglevel "quiet" \
         -i ${__imgSource} \
         -yvf scale=${resize}:-1 \
         ${__imgRepository}/Icon-${__imgDest}-${size}x${size}@${scale}x.png
   else
      # using imagemagick
      convert ${__imgSource} \
         -resize ${resize}x${resize} \
         -unsharp '1.5x1+0.7+0.02' \
         ${__imgRepository}/Icon-${__imgDest}-${size}x${size}@${scale}x.png
   fi
done

Original

Resizing