Take an image and output to various Android resolutions (ldpi - xxxhdpi)

make-android-icons.sh

#!/bin/sh

# make-android-icons.sh
# Author: Chad Armstrong
# Date: 11 December 2020
# Description: Take an image and output to various Android resolutions (ldpi - xxxhdpi)  
# This script runs under macOS and requires ImageMagick to be installed.


# Need ImageMagick first
# 1. How to download Homebrew and install it if not present
# /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# 2. Installing ImageMagick
# brew install imagemagick


# If there aren't the right parameters, display the Usage and bail out
if [ "$#" -ne 3 ]; then
    echo "Usage: make-android-icons file width height"
    exit -1
fi

# Get the command line parameters
# Parameters:
# filename: name of the original image
# width: custom width
# height: custom height
filename=$1

# Get the file name without an extension
# Reference: https://stackoverflow.com/questions/965053/extract-filename-and-extension-in-bash
name="${filename%%.*}"

# Get the custom width (set for the mdpi resolution)
width=$2

# Get the custom height (set for the mdpi resolution)
height=$3

# Generate folders
mkdir $name
mkdir $name/drawable-ldpi
mkdir $name/drawable-mdpi
mkdir $name/drawable-hdpi
mkdir $name/drawable-xhdpi
mkdir $name/drawable-xxhdpi
mkdir $name/drawable-xxxhdpi

# Scale the images
# Scaling ratio:: 3:4:6:8:12:16 

# LDPI @ 0.75x
convert -resize "$(($width*3/4))x$(($height*3/4))"! $filename "$name/drawable-ldpi/$name.png";

# MDPI @ 1.0x
convert -resize "$(($width))x$(($height))"! $filename "$name/drawable-mdpi/$name.png";

# HDPI @ 1.5x
convert -resize "$(($width*3/2))x$(($height*3/2))"! $filename "$name/drawable-hdpi/$name.png";

# XHDPI @ 2.0x
convert -resize "$(($width*2))x$(($height*2))"! $filename "$name/drawable-xhdpi/$name.png";

# XXHDPI @ 3.0x
convert -resize "$(($width*3))x$(($height*3))"! $filename "$name/drawable-xxhdpi/$name.png";

# XXHDPI @ 4.0x
convert -resize "$(($width*4))x$(($height*4))"! $filename "$name/drawable-xxxhdpi/$name.png";

# Once complete, open the new image directory in Finder
open $name