Generate placeholder icons for iOS apps that indicate their own size (in pixels).

generate_app_icons.sh

#!/bin/bash

# https://developer.apple.com/library/content/qa/qa1686/_index.html
function create_image() {
    COLOR=$1
    TEXT_COLOR=$2
    SIZE=$3
    NAME=$4

    convert -background "$COLOR" -fill white -font "Tahoma" -size $SIZEx$SIZE label:$SIZE "$NAME"
}

# Home screen on iPhone/iPod Touch with retina display
create_image '#ff0000' white 120 Icon-60@2x.png

# Home screen on iPhone with retina HD display
create_image '#ff0000' white 180 Icon-60@3x.png

# Home screen on iPad
create_image '#0000ff' white 76 Icon-76.png

# Home screen on iPad with retina display
create_image '#0000ff' white 152 Icon-76@2x.png

# Home screen on iPad Pro
create_image '#0000ff' white 167 Icon-83.5@2x.png

# Spotlight (should be Icon-Small-40.png)
create_image '#ff00ff' white 40 Icon-40.png

# Spotlight on devices with retina display (should be Icon-Small-40@2x.png)
create_image '#ff00ff' white 80 Icon-40@2x.png

# Spotlight on devices with retina HD display (should be Icon-Small-40@3x.png)
create_image '#ff00ff' white 120 Icon-40@3x.png

# Settings (should be Icon-Small.png)
create_image '#0000ff' white 29 Icon-29.png

# Settings on devices with retina display (should be Icon-Small@2x.png)
create_image '#ff00ff' white 58 Icon-29@2x.png

# Settings on devices with retina HD display (should be Icon-Small@3x.png)
create_image '#ff0000' white 87 Icon-29@3x.png

# iPhone Notification on devices with retina display
create_image '#ff0000' white 40 Icon-20@2x.png

# Notification
create_image '#ff00ff' white 20 Icon-20.png

# Notification on devices with retina display
create_image '#ff00ff' white 40 Icon-20@2x.png

# Notification on devices with retina HD display
create_image '#ff00ff' white 60 Icon-20@3x.png


# Home screen on Apple Watch (38mm/42mm), Long-Look notification on Apple Watch (38mm) (should be AppIcon40x40@2x.png)
create_image '#00ff00' black 80 WatchAppIcon-40@2x.png

# Long-Look notification on Apple Watch (42mm) (should be AppIcon44x44@2x.png)
create_image '#00ff00' black 88 WatchAppIcon-44@2x.png

# Short-Look notification on Apple Watch (38mm) (should be AppIcon86x86@2x.png)
create_image '#00ff00' black 172 WatchAppIcon-86@2x.png

# Short-Look notification on Apple Watch (42mm) (should be AppIcon98x98@2x.png)
create_image '#00ff00' black 196 WatchAppIcon-98@2x.png

# Notification center on Apple Watch (38mm) (should be AppIcon24x24@2x.png)
create_image '#00ff00' black 48 WatchAppIcon-24@2x.png

# Notification center on Apple Watch (42mm) (should be AppIcon27.5x27.5@2x.png)
create_image '#00ff00' black 55 WatchAppIcon-27.5@2x.png

# Settings in the Apple Watch companion app on iPhone (should be AppIcon29x29@2x.png)
create_image '#00ff00' black 58 WatchAppIcon-29@2x.png

# Settings in the Apple Watch companion app on iPhone 6 Plus (should be AppIcon29x29@3x.png)
create_image '#00ff00' black 87 WatchAppIcon-29@3x.png