Command-line image resizer for Bootstrap grid

respimg.rb

#!/usr/bin/env ruby

require 'pathname'
require 'optparse'
require 'ostruct'
require 'rmagick'

class RespImgs
  CONTAINER_WIDTH = { xs: 320, sm: 750, md: 970, lg: 1170 }
  NUM_COLUMNS = 12
  GUTTER_WIDTH = 30

  def self.calc(size, cols)
    return (((size.to_f / NUM_COLUMNS) * cols) - GUTTER_WIDTH)
  end

  def self.parse(args)
    options = OpenStruct.new

    opt_parser = OptionParser.new do |opts|
      opts.banner = 'Usage: respimg.rb [options]'

      opts.separator ''

      opts.on('-i FILE', 'Input file') do |file|
        pn = Pathname.new(file)
        options.path = pn.dirname.to_s
        options.file = pn.basename(pn.extname.to_s).to_s
        options.ext = pn.extname.to_s
      end

      opts.separator ''
      opts.separator 'Number of columns this image will occupy:'

      options.xs = CONTAINER_WIDTH[:xs] - GUTTER_WIDTH
      opts.on('--xs COLUMNS', Integer,
        'on extra small devices (< 768px)') do |cols|
        options.xs = calc(CONTAINER_WIDTH[:xs], cols).to_i
      end

      opts.on('-s', '--sm COLUMNS', Integer,
        'on small devices (≥ 768px)') do |cols|
        options.sm = calc(CONTAINER_WIDTH[:sm], cols).to_i
      end

      opts.on('-m', '--md COLUMNS', Integer,
        'on medium devices (≥ 992px)') do |cols|
        options.md = calc(CONTAINER_WIDTH[:md], cols).to_i
      end

      opts.on('-l', '--lg COLUMNS', Integer,
        'on large devices (≥ 1200px)') do |cols|
        options.lg = calc(CONTAINER_WIDTH[:lg], cols).to_i
      end
    end

    opt_parser.parse!(args)
    return options
  end

  def self.resize(orig, out, x, q)

    img = orig.resize_to_fit(x, 0)
    img.write(out) { self.quality = q }
    img.destroy!
  end

  def self.process(opts)
    base = opts.path + '/' + opts.file
    orig = Magick::Image::read(base + opts.ext).first
    files = {}

    if opts.sm && opts.sm <= orig.base_columns
      files[:sm] = base + '-sm' + opts.ext
      resize(orig, files[:sm], opts.sm, 85)
      if (opts.sm * 2 <= orig.base_columns)
        files[:sm2x] = base + '-sm@2x' + opts.ext
        resize(orig, files[:sm2x], opts.sm * 2, 80)
      end
    end

    if opts.md && opts.md <= orig.base_columns
      files[:md] = base + '-md' + opts.ext
      resize(orig, files[:md], opts.md, 85)
      if (opts.md * 2 <= orig.base_columns)
        files[:md2x] = base + '-md@2x' + opts.ext
        resize(orig, files[:md2x], opts.md * 2, 80)
      end
    end

    if opts.lg && opts.lg <= orig.base_columns
      files[:lg] = base + '-lg' + opts.ext
      resize(orig, files[:lg], opts.lg, 85)
      if (opts.lg * 2 <= orig.base_columns)
        files[:lg2x] = base + '-lg@2x' + opts.ext
        resize(orig, files[:lg2x], opts.lg * 2, 80)
      end
    end

    orig.destroy!
    return files
  end

  def self.slim(files)
    puts <<-DONE
          picture
            /[if IE 9]
              <video style='display: none;'>
    DONE

    if files[:lg] && files[:lg2x]
      puts <<-DONE
            source(srcset='#{files[:lg]} 1x, #{files[:lg2x]} 2x' media='(min-width: 1200px)')/
      DONE
    elsif files[:lg]
      puts <<-DONE
            source(srcset='#{files[:lg]}' media='(min-width: 1200px)')/
      DONE
    end

    if files[:md] && files[:md2x]
      puts <<-DONE
            source(srcset='#{files[:md]} 1x, #{files[:md2x]} 2x' media='(min-width: 992px)')/
      DONE
    elsif files[:md]
      puts <<-DONE
            source(srcset='#{files[:md]}' media='(min-width: 992px)')/
      DONE
    end

    if files[:sm] && files[:sm2x]
      puts <<-DONE
            source(srcset='#{files[:sm]} 1x, #{files[:sm2x]} 2x')/
      DONE
    elsif files[:sm]
      puts <<-DONE
            source(srcset='#{files[:sm]}')/
      DONE
    end

    puts <<-DONE
            /[if IE 9]
              </video>
    DONE

    if files[:sm] && files[:sm2x]
      puts <<-DONE
            img(srcset='#{files[:sm]} 1x, #{files[:sm2x]} 2x' alt='')/
      DONE
    elsif files[:sm]
      puts <<-DONE
            img(srcset='#{files[:sm]}' alt='')/
      DONE
    end
  end
end

options = RespImgs.parse(ARGV)
files = RespImgs.process(options)
RespImgs.slim(files)