magick_identify.rb

class MagickIdentify
  attr_reader :data
  
  def initialize(image_path)
    @image_path = image_path
    @data = {}
    execute_and_parse
  end
  
  def method_missing(method, *args)
    @data.key?(method) ? @data[method] : super(method, *args)
  end
  
  private
  
  def execute_and_parse
    @output = %x{identify -format "#{format}" #{@image_path}}.chomp
    parse
  end
  
  def parse
    @output.split(/\n/).each do |feature_line|
      feature_name, feature_output = feature_line.split(/-/)
      @data[feature_name.to_sym] = feature_output
    end
  end
  
  def format
    format_string = ""
    features.each do |feature, syntax|
      format_string << "#{feature}-#{syntax}\n"
    end
    format_string
  end
  
  def features
    {
      :file_size => '%b',
      :comment => '%c',
      :directory => '%d',
      :filename_extension => '%e',
      :filename => '%f',
      :page_geometry => '%g',
      :height => '%[height]',
      :input_filename => '%i',
      :number_of_unique_colors => '%k',
      :label => '%l',
      :output_filename => '%o',
      :width => '%[width]',
      :x_resolution => '%x',
      :y_resolution => '%y',
      :page_height => '%H',
      :page_width => '%W',
      :base => '%[base]',
      :directory => '%[directory]',
      :extension => '%[extension]',
      :size => '%[size]'
    }
  end
end

magick_identify_spec.rb

require 'magick_identify'
require 'spec'

describe "MagickIdentify" do
  before do
    @a = MagickIdentify.new(image_path)
  end
  
  it "should return 'example'" do
    @a.base.should == "example"
  end
  
  private
  
  def image_path
    File.expand_path(File.dirname(__FILE__) + '/files/example.png')
  end
end