A simple bash script to create icons for your website/PWA

icons.sh

#!/usr/bin/env bash

if [ $# == 0 ]; then
    echo "Usage: $0 param1 [param2]"
    echo "* param1: png image (best 512x512)"
    echo "* param2: folder for images, default: static/"
    exit
fi

#check if imagemagick is installed and fail otherwise
command -v convert >/dev/null 2>&1
if [[ $? -ne 0 ]]; then
    echo "Imagemagick is required to resize images!"
    exit 1
fi

mkdir ${2-static}

convert $1 -resize 36x36 ${2-static}/android-icon-36x36.png
convert $1 -resize 48x48 ${2-static}/android-icon-48x48.png
convert $1 -resize 72x72 ${2-static}/android-icon-72x72.png
convert $1 -resize 96x96 ${2-static}/android-icon-96x96.png
convert $1 -resize 144x144 ${2-static}/android-icon-144x144.png
convert $1 -resize 192x192 ${2-static}/android-icon-192x192.png
convert $1 -resize 256x256 ${2-static}/android-icon-256x256.png
convert $1 -resize 512x512 ${2-static}/android-icon-512x512.png

convert $1 -resize 57x57 ${2-static}/apple-icon-57x57.png
convert $1 -resize 60x60 ${2-static}/apple-icon-60x60.png
convert $1 -resize 72x72 ${2-static}/apple-icon-72x72.png
convert $1 -resize 76x76 ${2-static}/apple-icon-76x76.png
convert $1 -resize 114x114 ${2-static}/apple-icon-114x114.png
convert $1 -resize 120x120 ${2-static}/apple-icon-120x120.png
convert $1 -resize 144x144 ${2-static}/apple-icon-144x144.png
convert $1 -resize 152x152 ${2-static}/apple-icon-152x152.png
convert $1 -resize 180x180 ${2-static}/apple-icon-180x180.png

convert $1 -resize 70x70 ${2-static}/ms-icon-70x70.png
convert $1 -resize 144x144 ${2-static}/ms-icon-144x144.png
convert $1 -resize 150x150 ${2-static}/ms-icon-150x150.png
convert $1 -resize 310x310 ${2-static}/ms-icon-310x310.png

convert $1 -resize 16x16 ${2-static}/favicon-16x16.png
convert $1 -resize 16x16 ${2-static}/favicon-16x16.png
convert $1 -resize 32x32 ${2-static}/favicon-32x32.png
convert $1 -resize 96x96 ${2-static}/favicon-96x96.png

cat << EOF > links.html
    <link rel="apple-touch-icon" sizes="57x57" href="${2-static}/apple-icon-57x57.png" />
	<link rel="apple-touch-icon" sizes="60x60" href="${2-static}/apple-icon-60x60.png" />
	<link rel="apple-touch-icon" sizes="72x72" href="${2-static}/apple-icon-72x72.png" />
	<link rel="apple-touch-icon" sizes="76x76" href="${2-static}/apple-icon-76x76.png" />
	<link rel="apple-touch-icon" sizes="114x114" href="${2-static}/apple-icon-114x114.png" />
	<link rel="apple-touch-icon" sizes="120x120" href="${2-static}/apple-icon-120x120.png" />
	<link rel="apple-touch-icon" sizes="144x144" href="${2-static}/apple-icon-144x144.png" />
	<link rel="apple-touch-icon" sizes="152x152" href="${2-static}/apple-icon-152x152.png" />
	<link rel="apple-touch-icon" sizes="180x180" href="${2-static}/apple-icon-180x180.png" />
	<link rel="icon" type="image/png" sizes="192x192" href="${2-static}/android-icon-192x192.png" />
	<link rel="icon" type="image/png" sizes="32x32" href="${2-static}/favicon-32x32.png" />
	<link rel="icon" type="image/png" sizes="96x96" href="${2-static}/favicon-96x96.png" />
	<link rel="icon" type="image/png" sizes="16x16" href="${2-static}/favicon-16x16.png" />
	<link rel="manifest" href="${2-static}/manifest.json" />
EOF

cat << EOF > ${2-static}/manifest.json
{
    "short_name": "",
    "name": "",
    "lang": "en",
    "description": "",
    "start_url": "/",
    "background_color": "#",
    "theme_color": "#",
    "dir": "ltr",
    "display": "",
    "orientation": "",
	"display": "standalone",

    "icons": [
		{
			"src": "/static/android-icon-36x36.png",
			"sizes": "36x36",
			"type": "image/png",
			"density": "0.75"
		},
		{
			"src": "/static/android-icon-48x48.png",
			"sizes": "48x48",
			"type": "image/png",
			"density": "1.0"
		},
		{
			"src": "/static/android-icon-72x72.png",
			"sizes": "72x72",
			"type": "image/png",
			"density": "1.5"
		},
		{
			"src": "/static/android-icon-96x96.png",
			"sizes": "96x96",
			"type": "image/png",
			"density": "2.0"
		},
		{
			"src": "/static/android-icon-144x144.png",
			"sizes": "144x144",
			"type": "image/png",
			"density": "3.0"
		},
		{
			"src": "/static/android-icon-192x192.png",
			"sizes": "192x192",
			"type": "image/png",
			"density": "4.0"
		},
        {
			"src": "/static/android-icon-256x256.png",
			"sizes": "256x256",
			"type": "image/png",
            "density": "1.5"
		},
        {
            "src": "/static/android-icon-512x512.png",
            "sizes": "512x512",
            "type": "image/png",
            "density": "4.0"
        }
	]
}
EOF

cat << EOF > ${2-static}/browserconfig.xml
<?xml version="1.0" encoding="utf-8"?>
<browserconfig>
    <msapplication>
        <tile>
            <square70x70logo src="/ms-icon-70x70.png"/>
            <square150x150logo src="/ms-icon-150x150.png"/>
            <square310x310logo src="/ms-icon-310x310.png"/>
            <TileColor>#ffffff</TileColor>
        </tile>
    </msapplication>
</browserconfig>
EOF

curl https://gist.githubusercontent.com/rcastellotti/88459478d98811f2b36d02b25cc57249/raw/ | bash -s -- favicon.png

thx @fedfontana for the update