generates in-line image tag (html)

inline_image.rb

#!/usr/bin/env ruby
# coding: UTF-8

# inline_image.rb
# 
# generates in-line image tag
# (referenced: http://en.wikipedia.org/wiki/Data_URI_scheme)
# 
# created on : 2013.06.30
# last update: 2013.06.30
# 
# by [email protected]

require "rubygems"
require "base64"

def print_usage
  puts "* usage: #{__FILE__} [IMAGE_FILE_PATH]"
end

def image_file_type(filepath)
  filemagic = ""
  begin
    if Gem::Specification.find_by_name "ruby-filemagic" # gem install ruby-filemagic
      require "filemagic"
      filemagic = FileMagic.new.file(filepath)
    end
  rescue
    `which file`
    if $?.exitstatus == 0
      filemagic = `file "#{filepath}"`
    else
      raise "'filemagic' and 'file' are not installed"
    end 
  end
  case
  when filemagic =~ /^jpeg image data/i
    filemagic = "image/jpg"
  when filemagic =~ /^gif image data/i
    filemagic = "image/gif"
  when filemagic =~ /^png image data/i
    filemagic = "image/png"
  else
    filemagic = "application/octet-stream"
  end
  return filemagic
end

def generate_tag(filepath)
  type = image_file_type(filepath)
  base64 = ""
  File.open(filepath, "r"){|f|
    base64 = Base64.encode64(f.read).gsub("\n", "")
  }
  return "<img src=\"data:#{type};base64,#{base64}\" alt=\"#{File.basename(filepath)}\">"
end

if __FILE__ == $0
  if ARGV.count < 1 || !(File.exists? File.expand_path(ARGV[0]))
    print_usage
  else
    puts generate_tag(File.expand_path(ARGV[0]))
  end
end