Image resize and optimize script

downsize.rb

#!/usr/bin/env ruby

#
# Downsizes and optimizes (for size) an image so that it can be suitably/easily
# sent to people via email.
#

TARGET_DIR = "#{Dir.home}/Downloads"
TARGET_WIDTH = 2000

#
# ---
#

CACHED_HOMEBREW_PATHS = {}
def get_homebrew_path(package)
  CACHED_HOMEBREW_PATHS[package] ||= begin
    brew_path = run_command("brew --prefix #{package}", abort: false)
    if !brew_path
      abort("Homebrew package #{package} may be unavailable; try `brew install #{package}`")
    end
    brew_path
  end
end

def run_command(command, abort: true)
  ret = `#{command}`
  if $? != 0
    if abort
      abort("command failed: #{command}")
    else
      return false
    end
  end
  ret.strip
end

#
# ---
#

def main
  unless Dir.exists?(TARGET_DIR)
    abort("Target dir does not exist: #{TARGET_DIR}")
  end

  magick_path = get_homebrew_path("imagemagick")
  mozjpeg_path = get_homebrew_path("mozjpeg")

  abort("need at least one file as argument") if ARGV.empty?
  ARGV.each do |filename|
    width, height =
      run_command(%{#{magick_path}/bin/magick convert #{filename} -format "%[w] %[h]" info:}).
      split

    target_proportion = if width > height
      "#{TARGET_WIDTH}x" # landscape
    else
      "x#{TARGET_WIDTH}" # portrait
    end

    target_filename = "#{TARGET_DIR}/#{File.basename(filename, ".*")}.jpg"

    run_command("#{magick_path}/bin/magick convert #{filename} -resize #{target_proportion} -quality 85 JPEG:- | #{mozjpeg_path}/bin/cjpeg -outfile #{target_filename} -optimize -progressive")
    puts "Created: #{target_filename}"
  end
end

#
# ---
#

main