Set himawari wallpaper shell script for macOS. (Linux & Windows not tested)

set-himawari-wallpaper.sh

#!/bin/bash

PATH=$PATH:/usr/local/bin
echo `date`

echo "Checking himawari"
if ! type himawari > /dev/null; then
    echo "Install himawari with:"
    echo
    echo "brew install imagemagick"
    echo "brew install graphicsmagick"
    echo "npm i himawari -g"
    echo
else
    mkdir -p /tmp/himawari
    # Recommended values: 2160p(UHD/4K) use zoom 2; 4320p(8K) use zoom 3; 8640p(16K) use zoom 4;
    echo "Downloading latest image"
    himawari --zoom 2 --parallel --timeout 300000 --outfile /tmp/himawari/
fi

echo "Checking wallpaper"
if ! type wallpaper > /dev/null; then
    echo "Install wallpaper with:"
    echo
    echo "brew install wallpaper"
    echo
else
    # If download succeeded, $image will be the latest image.
    image=`find /tmp/himawari/himawari-*.jpg | tail -1`
    current=`wallpaper get --screen main`
    change=0
    if [[ $current =~ ^/tmp/himawari/himawari-[0-9]*.jpg$ ]]; then
	# If $current is himawari, update wallpaper without ask user.
	change=1
    else
	# If $current is not himawari, ask user. 
	echo "Your current wallpaper is $current."
	read -t 60 -r -p "Do you want to change? [Y/n] " input
        case $input in
            [yY][eE][sS]|[yY])
                change=1
                ;;
            [nN][oO]|[nN])
                change=0
                ;;
            *)
                echo "Invalid input..."
                exit 1
                ;;
        esac
    fi
    # If download not succeeded, do not change wallpaper.
    if [[ $change -eq 1 && $image != $current ]]; then
	wallpaper set $image --screen main --scale fit
	current=`wallpaper get --screen main`
	echo "Wallpaper is changed to $current"
    else
	echo "Wallpaper is not changed"
    fi
fi

Example:
Put set-himawari-wallpaper.sh file in ~/bin/
Run ~/bin/set-himawari-wallpaper.sh and answer yes
Save the following as ~/Library/LaunchAgents/com.hackinggate.set-himawari-wallpaper.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key>
  <string>com.hackinggate.set-himawari-wallpaper</string>
  <key>ProgramArguments</key>
  <array>
    <string>sh</string>
    <string>-c</string>
    <string>
      $HOME/bin/set-himawari-wallpaper.sh
    </string>
  </array>
  <key>StartInterval</key>
  <integer>600</integer>
  <key>RunAtLoad</key>
  <true/>
  <key>StandardErrorPath</key>
  <string>/tmp/com.hackinggate.set-himawari-wallpaper.stderr.log</string>
  <key>StandardOutPath</key>
  <string>/tmp/com.hackinggate.set-himawari-wallpaper.stdout.log</string>
</dict>
</plist>

Load as launchctl service

launchctl load ~/Library/LaunchAgents/com.hackinggate.set-himawari-wallpaper.plist

https://alvinalexander.com/mac-os-x/mac-osx-startup-crontab-launchd-jobs
https://stackoverflow.com/a/26586170/4063462