A Shell script to generate .ico and .icns files (mac/windows app icons) from a single PNG

generate-icns.sh

#!/bin/bash
# Required deps:
# imagemagick: https://imagemagick.org/script/download.php
# iconutil: https://developer.apple.com/library/archive/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Optimizing/Optimizing.html

# name of your master icon, should be 1024x1024 or .svg
if [ -z "$PNG_MASTER" ]; then
    # If not set, assign a default value
    PNG_MASTER="icon-large.png"
fi

ICONSET_FOLDER="AppIcon.iconset"
sizes=(
  16
  32
  128
  256
  512
)

# Generate renditions at the sizes in "sizes" above, put all in ICONSET_FOLDER
mkdir -p $ICONSET_FOLDER
for size in "${sizes[@]}"; do
  icon="icon_${size}.png"
  ICON_FILES="$ICON_FILES $ICONSET_FOLDER/$icon"
  echo Generating $ICONSET_FOLDER/$icon
  convert $PNG_MASTER -quality 100 -resize ${size}x${size} $ICONSET_FOLDER/$icon

  icon="icon_${size}x${size}@2x.png"
  ICON_FILES="$ICON_FILES $ICONSET_FOLDER/$icon"
  echo Generating $ICONSET_FOLDER/$icon
  hires=$((size * 2))
  convert $PNG_MASTER -quality 100 -resize ${hires}x${hires} $ICONSET_FOLDER/$icon
done

# generate icon.icns for mac app (this only works on mac)
echo Generating icon.icns
iconutil -c icns $ICONSET_FOLDER -o icon.icns

# Generate .ico file for windows
ICON_FILES=""
for size in "${sizes[@]}"; do
  ICON_FILES="$ICON_FILES $ICONSET_FOLDER/icon_${size}.png"
  ICON_FILES="$ICON_FILES $ICONSET_FOLDER/icon_${size}x${size}@2x.png"
done
echo Generating icon.ico
convert $ICON_FILES icon.ico

# remove generated renditions
echo removing $ICONSET_FOLDER folder
rm -rf $ICONSET_FOLDER