TIFFなりなんなりの無圧縮or可逆圧縮データからImageMagick経由で可逆圧縮PNGを生成した後に、pngquantで減色する (文字中心データ対象なら--speed は10で十分。標準の3だとめっちゃ遅い)

convert_png_and_decrease_color.rb

# coding: us-ascii

require 'logger'

sources = ARGV.dup
abort "Pass target sources." if sources.empty?

class MultiLogger
  def initialize(*destinations)
    @destinations = destinations.map { |dst| Logger.new dst }
  end

  Logger.instance_methods.each do |meth|
    define_method meth do |*args, &block|
      @destinations.each { |dst| dst.__send__ meth, *args, &block }
    end
  end
end

color = 16
imagemagick = 'convert'
pngquant = 'pngquant'
logger = MultiLogger.new $stdout, 'PNG-oprations.log'
failures = []

sources.each do |source|
  basepath, _, extname = source.rpartition('.')
  source_type = extname.upcase
  basename = File.basename basepath
  lossless_png = "#{basepath}.png"
  result = "#{basepath}_#{color}color.png"

  begin
    logger << "#{basename}: Converting #{source_type} to lossless PNG\n"
    `#{imagemagick} #{source} -compress LossLess #{lossless_png}`
    logger << "#{basename}: Decreasing the PNG color to #{color}\n"
    `#{pngquant} --ext _#{color}color.png --speed 10 #{color} #{lossless_png}`

    raise 'Ouch! ><' unless File.exist? result
  rescue Exception => err
    failures << basename
    logger.fatal "#{basename}: Failed: #{err}\n"
  else
    File.delete source
    File.delete lossless_png
    logger << "#{basename}: Success\n"
  end
end

logger.<<(failures.empty? ? "Yatta! ^^\n" : "Akankatta! >< #{failures.inspect}\n")