png_info

#!/usr/bin/env ruby
require File.join( File.dirname( __FILE__ ), '..', 'lib', 'css-spriter' )

module PNG
  class Parser
    def go!( file )
      check_header( file )

      while(! file.eof?) do
        parse_chunk(file)
      end
    end

  private
    def check_header( file )
      header = file.read(8)
      raise "Invalid PNG file header" unless ( header == FileHeader.new.encode)
    end

    def parse_chunk(f)
      len = f.read(4).unpack("N")
      type = f.read(4)
      data = f.read(len[0])
      crc = f.read(4)
      handle(type, len, data )
    end

    def handle( type, len, data )
      case type
      when "IHDR"
        attrs = data.unpack("N2C5")
        puts "PNG width: #{attrs[0]}"
        puts "PNG height: #{attrs[1]}"
        puts "PNG depth: #{attrs[2]}"
        puts "PNG color type: #{attrs[3]}"
        puts "PNG compression method: #{attrs[4]}"
        puts "PNG filter method: #{attrs[5]}"
        puts "PNG interlace method: #{attrs[6]}"
      end

      puts "PNG block #{type}"
      puts "length: #{len}"
    end
  end


  class Info
    def self.open( file_name )
      @parser = Parser.new

      name = File.basename( file_name, ".png" )

      File.open(file_name, "r") do |f|
        @parser.go!( f )
      end
    end
  end
end


PNG::Info.open( ARGV[0] )