shell script for generating iOS and Android icons from source images. It needs Python3 (or virtualenv) and CairoSVG installed to work (http://cairosvg.org/).

genicons.sh

#!/bin/bash
RED_ON='\e[0;31m'; 
GREEN_ON='\e[0;32m'; 
YELLOW_ON='\e[0;33m' 
OFF='\e[0m'

# Python 3 Virtual Env !!! replace with your own !!!
source ~/Projects/tensorflowp3/bin/activate

# Set arguments
while getopts "p:i:" opt
do
    case "$opt" in
    p) PLATFORM=$OPTARG;;
    i) FILES_STRING=$OPTARG;;
    esac
done

if [[ -z "${PLATFORM}" || -z "${FILES_STRING}" ]]; then
    printf "${RED_ON}MISSING REQUIRED ARGUMENT\n${OFF}"
    printf "usage: genicons -p platform -i inputfiles\n"
    printf "\t-p\tplatform: [ios, droid-launch, droid-menu, droid-context, droid-notif]\n"
    printf "\t-i\tinput files separated by a comma (ex: inputfile1,inputfile2,etc)\n"
    exit 1
fi

FILES=(${FILES_STRING//,/ })

DROID_MDPI=160
DROID_HDPI=240
DROID_XHDPI=320
DROID_XXHDPI=480
DROID_XXXHDPI=640

checkDroidDirs() {
    if [ ! -d "$1/drawable" ]; then 
        printf "${YELLOW_ON}Making drawable directory...\n${OFF}"
        mkdir -p "$1/drawable"
    fi
    
    if [ ! -d "$1/drawable-hdpi" ]; then
        printf "${YELLOW_ON}Making drawable-hdpi directory...\n${OFF}"
        mkdir -p "$1/drawable-hdpi"
    fi

    if [ ! -d "$1/drawable-xhdpi" ]; then
        printf "${YELLOW_ON}Making drawable-xhdpi directory...\n${OFF}"
        mkdir -p "$1/drawable-xhdpi"
    fi

    if [ ! -d "$1/drawable-xxhdpi" ]; then
        printf "${YELLOW_ON}Making drawable-xxhdpi directory...\n${OFF}"
        mkdir -p "$1/drawable-xxhdpi"
    fi

    if [ ! -d "$1/drawable-xxxhdpi" ]; then
        printf "${YELLOW_ON}Making drawable-xxxhdpi directory...\n${OFF}"
        mkdir -p "$1/drawable-xxxhdpi"
    fi
}

for i in "${FILES[@]}"
do
   : 
   # do whatever on $i
   printf "Converting ${GREEN_ON}${i}\n${OFF}"
   basepath=$(dirname "${i}")
   filename="${i%.*}"

    # Android: Launcher - (PNG)
    if [ "${PLATFORM}" == "droid-launch" ]; then
        checkDroidDirs "${basepath}"
        # mdpi    -  48x48  - 160 dpi
        cairosvg -f png -W 48 -H 48 -d ${DROID_MDPI} $i -o "${basepath}/drawable/launch_${filename}.png"
        # hdpi    -  72x72  - 240 dpi
        cairosvg -f png -W 72 -H 72 -d ${DROID_HDPI} $i -o "${basepath}/drawable-hdpi/launch_${filename}.png"
        # xhdpi   -  96x96  - 320 dpi
        cairosvg -f png -W 96 -H 96 -d ${DROID_XHDPI} $i -o "${basepath}/drawable-xhdpi/launch_${filename}.png"
        # xxhdpi  - 144x144 - 480 dpi
        cairosvg -f png -W 144 -H 144 -d ${DROID_XXHDPI} $i -o "${basepath}/drawable-xxhdpi/launch_${filename}.png"
        # xxxhdpi - 192x192 - 640 dpi
        cairosvg -f png -W 192 -H 192 -d ${DROID_XXXHDPI} $i -o "${basepath}/drawable-xxxhdpi/launch_${filename}.png"
        # Play    - 512x512 -  72 dpi
        cairosvg -f png -W 512 -H 512 -d 72 $i -o "${basepath}/drawable/launch_${filename}_playstore.png"
    fi 

    # Android: Action, Dialog, Tab (PNG)
    if [ "${PLATFORM}" == "droid-menu" ]; then
        checkDroidDirs "${basepath}"
        # mdpi    - 24x24 - 160 dpi
        cairosvg -f png -W 24 -H 24 -d ${DROID_MDPI} $i -o "${basepath}/drawable/menu_${filename}.png"
        # hdpi    - 36x36 - 240 dpi
        cairosvg -f png -W 36 -H 36 -d ${DROID_HDPI} $i -o "${basepath}/drawable-hdpi/menu_${filename}.png"
        # xhdpi   - 48x48 - 320 dpi
        cairosvg -f png -W 48 -H 48 -d ${DROID_XHDPI} $i -o "${basepath}/drawable-xhdpi/menu_${filename}.png"
        # xxhdpi  - 72x72 - 480 dpi
        cairosvg -f png -W 72 -H 72 -d ${DROID_XXHDPI} $i -o "${basepath}/drawable-xxhdpi/menu_${filename}.png"
        # xxxhdpi - 96x96 - 640 dpi
        cairosvg -f png -W 96 -H 96 -d ${DROID_XXXHDPI} $i -o "${basepath}/drawable-xxxhdpi/menu_${filename}.png"
    fi

    # Android: Small contextual (PNG)
    if [ "${PLATFORM}" == "droid-context" ]; then
        checkDroidDirs "${basepath}"
        # mdpi    - 16x16 - 160 dpi
        cairosvg -f png -W 16 -H 16 -d ${DROID_MDPI} $i -o "${basepath}/drawable/context_${filename}.png"
        # hdpi    - 24x24 - 240 dpi
        cairosvg -f png -W 24 -H 24 -d ${DROID_HDPI} $i -o "${basepath}/drawable-hdpi/context_${filename}.png"
        # xhdpi   - 32x32 - 320 dpi
        cairosvg -f png -W 32 -H 32 -d ${DROID_XHDPI} $i -o "${basepath}/drawable-xhdpi/context_${filename}.png"
        # xxhdpi  - 48x48 - 480 dpi
        cairosvg -f png -W 48 -H 48 -d ${DROID_XXHDPI} $i -o "${basepath}/drawable-xxhdpi/context_${filename}.png"
        # xxxhdpi - 64x64 - 640 dpi
        cairosvg -f png -W 64 -H 64 -d ${DROID_XXXHDPI} $i -o "${basepath}/drawable-xxxhdpi/context_${filename}.png"
    fi

    # Android: Notification (PNG)
    if [ "${PLATFORM}" == "droid-notif" ]; then
        checkDroidDirs "${basepath}"
        # mdpi    - 22x22 - 160 dpi
        cairosvg -f png -W 22 -H 22 -d ${DROID_MDPI} $i -o "${basepath}/drawable/notify_${filename}.png"
        # hdpi    - 33x33 - 240 dpi
        cairosvg -f png -W 33 -H 33 -d ${DROID_HDPI} $i -o "${basepath}/drawable-hdpi/notify_${filename}.png"
        # xhdpi   - 44x44 - 320 dpi
        cairosvg -f png -W 44 -H 44 -d ${DROID_XHDPI} $i -o "${basepath}/drawable-xhdpi/notify_${filename}.png"
        # xxhdpi  - 66x66 - 480 dpi
        cairosvg -f png -W 66 -H 66 -d ${DROID_XXHDPI} $i -o "${basepath}/drawable-xxhdpi/notify_${filename}.png"
        # xxxhdpi - 88x88 - 640 dpi
        cairosvg -f png -W 88 -H 88 -d ${DROID_XXXHDPI} $i -o "${basepath}/drawable-xxxhdpi/notify_${filename}.png"
    fi

    #iOS: SVG -> PDF
    if [ "${PLATFORM}" == "ios" ]; then
        if [ ! -d "${basepath}/ios" ]; then
            printf "${YELLOW_ON}Making iOS folder...\n${OFF}"
            mkdir -p "${basepath}/ios"
        fi
        cairosvg -f pdf $i -o "${basepath}/ios/${filename}.pdf"
    fi
done