Convert SVG file to macOS icon (icns) format

svg2icns.sh

#!/bin/sh -x

set -e

SIZES="
16,16x16
32,16x16@2x
32,32x32
64,32x32@2x
128,128x128
256,128x128@2x
256,256x256
512,256x256@2x
512,512x512
1024,512x512@2x
"

for SVG in "$@"; do
    BASE=$(basename "$SVG" | sed 's/\.[^\.]*$//')
    ICONSET="$BASE.iconset"
    mkdir -p "$ICONSET"
    for PARAMS in $SIZES; do
        SIZE=$(echo $PARAMS | cut -d, -f1)
        LABEL=$(echo $PARAMS | cut -d, -f2)
        svg2png -w $SIZE -h $SIZE -i "$SVG" -o "$ICONSET"/icon_$LABEL.png
    done

    iconutil -c icns "$ICONSET"
    rm -rf "$ICONSET"
done

Based on previous contributions, made this shell function which works for me, input is a single file or more. tested with zsh

function svg_to_icns(){
    local RESOLUTIONS=(
        16,16x16
        32,16x16@2x
        32,32x32
        64,32x32@2x
        128,128x128
        256,128x128@2x
        256,256x256
        512,256x256@2x
        512,512x512
        1024,512x512@2x
    )

    for SVG in $@; do
      BASE=$(basename "$SVG" | sed 's/\.[^\.]*$//')
        ICONSET="$BASE.iconset"
        ICONSET_DIR="./icons/$ICONSET"
        mkdir -p "$ICONSET_DIR"
        for RES in ${RESOLUTIONS[@]}; do
            SIZE=$(echo $RES | cut -d, -f1)
            LABEL=$(echo $RES | cut -d, -f2)
            svg2png -w $SIZE -h $SIZE "$SVG" "$ICONSET_DIR"/icon_$LABEL.png
        done

        iconutil -c icns "$ICONSET_DIR"
    done
}

Example usage

$ svg2png -V
0.1.3
$ svg_to_icns notepad.svg
$ file icons/notepad.icns
notepad.icns: Mac OS X icon, 100192 bytes, "ic12" type

You can also turn this into a script, add set -e at least for exiting on error, however then the script must be in your path if you want to be able to invoke it from anywhere, or use as an alias with full path.