A simple Ruby script for preparing resized drawable images for multiple DPIs on Android.

andr

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-
#
# Copyright (C) 2013 Yuichi Araki
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
#
# $ andr path/to/drawable-xxxhdpi/FILE
# -> drawable-xxhdpi/FILE drawable-xhdpi/FILE, drawable-hdpi/FILE, drawable-mdpi/FILE, drawable-ldpi/FILE
#
# $ andr path/to/drawable-xxhdpi/FILE
# -> drawable-xhdpi/FILE, drawable-hdpi/FILE, drawable-mdpi/FILE, drawable-ldpi/FILE

class Size

  attr_accessor :width, :height

  def initialize(width, height)
    @width = width
    @height = height
  end

  def to_s
    "#{@width} x #{@height}"
  end

end

class Strategy

  RATIOS = {
    :ldpi => 120,
    :mdpi => 160,
    :tvdpi => 213,
    :hdpi => 240,
    :xhdpi => 320,
    :xxhdpi => 480,
    :xxxhdpi => 640
  }

  def initialize(filename)
    # The original file
    @original_file = File.expand_path(filename)
    @filename = File.basename(filename)
    # The orignal DPI
    segments = @original_file.split(File::SEPARATOR)
    parent_dir = segments[-2]
    @original_dpi = parse_dpi(parent_dir)
    @original_dir = File.dirname(@original_file)
    @parent_dir = File.expand_path(File.join(@original_dir, '..'))
    # Target DPIs
    collect_target_dpis
    # Original image size
    @original_size = detect_image_size(filename)
  end

  def collect_target_dpis
    @target_dpis = []
    return if @original_dpi == :ldpi
    @target_dpis.push :ldpi if File.directory?(File.join(@original_dir, '..', 'drawable-ldpi'))
    return if @original_dpi == :mdpi
    @target_dpis.push :mdpi if File.directory?(File.join(@original_dir, '..', 'drawable-mdpi'))
    return if @original_dpi == :tvdpi
    @target_dpis.push :tvdpi if File.directory?(File.join(@original_dir, '..', 'drawable-tvdpi'))
    return if @original_dpi == :hdpi
    @target_dpis.push :hdpi if File.directory?(File.join(@original_dir, '..', 'drawable-hdpi'))
    return if @original_dpi == :xhdpi
    @target_dpis.push :xhdpi if File.directory?(File.join(@original_dir, '..', 'drawable-xhdpi'))
    return if @original_dpi == :xxhdpi
    @target_dpis.push :xxhdpi if File.directory?(File.join(@original_dir, '..', 'drawable-xxhdpi'))
    return if @original_dpi == :xxxhdpi
    @target_dpis.push :xxxhdpi if File.directory?(File.join(@original_dir, '..', 'drawable-xxxhdpi'))
  end

  def command(to)
    w = @original_size.width * RATIOS[to] / RATIOS[@original_dpi]
    h = @original_size.height * RATIOS[to] / RATIOS[@original_dpi]
    f = File.join(@parent_dir, "drawable-#{to}", @filename)
    "sips -z #{h} #{w} #{@original_file} -o #{f}"
  end

  def commands
    @target_dpis.map {|dpi| command(dpi) }
  end

  def carry_out!
    puts self.to_s
    commands.each do |c|
      puts c
      break unless system c
    end
  end

  def to_s
    "#{@original_dpi}: #{@original_size}: #{@target_dpis.join(', ')}"
  end

  def parse_dpi(dir)
    case dir
    when 'drawable-xxxhdpi'
      :xxxhdpi
    when 'drawable-xxhdpi'
      :xxhdpi
    when 'drawable-xhdpi'
      :xhdpi
    when 'drawable-hdpi'
      :hdpi
    when 'drawable-mdpi'
      :mdpi
    when 'drawable-ldpi'
      :ldpi
    else
      raise 'Invalid directory'
    end
  end

  def detect_image_size(filename)
    result = `file #{filename}`
    md = result.match(/([1-9][0-9]*) x ([1-9][0-9]*)/)
    Size.new(md[1].to_i, md[2].to_i)
  end

end

strategy = Strategy.new(ARGV[0])
strategy.carry_out!