favicon.sh

#!/bin/bash
# Converts an image in a multi-resolution favicon
# Requires Imagemagick

function generate_favicon() {

command -v convert >/dev/null 2>&1 || (echo "Imagemagick not here, install it" && return )
case "$#" in
  "0")
    echo "Usage: $FUNCNAME input.png output.ico"
    echo -e "\t or $FUNCNAME input.png"
    echo "Work with png, jpg and jpeg file"
    return
  ;;
  "1")
    input="$1"
    # rename jpg, jpeg and png to output ico
    output="${input/.png/.ico}"
    output="${output/.jpg/.ico}"
    output="${output/.jpeg/.ico}"
  ;;
  "2")
    input="$1"
    output="$2"
  ;;
esac

sizes="16 32 64 128 256"
tmp_dir=$(mktemp -d /tmp/favicon.XXXXXXXXXX)
files=""

for size in $sizes; do
    file="$tmp_dir/$size.png"
    convert "$input" -depth 8 -background transparent -flatten -resize "${size}x${size}" "$file"
    files="$files $file"
done

convert $files $output
rm -R $tmp_dir
}