#--
# PDF::Writer for Ruby.
#   http://rubyforge.org/projects/ruby-pdf/
#   Copyright 2003 - 2005 Austin Ziegler.
#
#   Licensed under a MIT-style licence. See LICENCE in the main distribution
#   for full licensing information.
#
# $Id: image.rb,v 1.2 2005/05/16 03:59:21 austin Exp $
#++
require 'pdf/writer/oreader'

  # an image object, will be an XObject in the document, includes description and data
class PDF::Writer::External::Image < PDF::Writer::External
  attr_reader :label
  attr_reader :image_info

  def initialize(parent, data, image, label)
    super(parent)

    @data = data

    @image_info = image

    @info = {
      'Type'    => '/XObject',
      'Subtype' => '/Image',
      'Width'   => image.width,
      'Height'  => image.height
    }

    case image.format
    when "JPEG"
      case image.channels
      when 1
        @info['ColorSpace'] = '/DeviceGray'
      when 4
        @info['ColorSpace'] = '/DeviceCMYK'
          # This should fix problems with CMYK JPEG colours inverted in
          # Adobe Acrobat. Enable only if appropriate.
#       @info['Decode'] = '[1.0 0.0 1.0 0.0 1.0 0.0 1.0 0.0]'
      else
        @info['ColorSpace'] = '/DeviceRGB'
      end
      @info['Filter'] = '/DCTDecode'
      @info['BitsPerComponent'] = 8
    when "PNG"
      if image.info[:compression_method] != 0
        raise TypeError, PDF::Writer::Message[:png_unsupp_compres]
      end

      if image.info[:filter_method] != 0
        raise TypeError, PDF::Writer::Message[:png_unsupp_filter]
      end

      data = data.dup
      data.extend(PDF::Writer::OffsetReader)

      data.read_o(8)  # Skip the default header

      ok      = true
      length  = data.size
      palette = ""
      idat    = ""

      while ok
        chunk_size  = data.read_o(4).unpack("N")[0]
        section     = data.read_o(4)
        case section
        when 'PLTE'
          palette << data.read_o(chunk_size)
        when 'IDAT'
          idat << data.read_o(chunk_size)
        when 'tRNS'
            # This chunk can only occur once and it must occur after the
            # PLTE chunk and before the IDAT chunk
          trans = {}
          case image.info[:color_type]
          when 3
              # Indexed colour, RGB. Each byte in this chunk is an alpha for
              # the palette index in the PLTE ("palette") chunk up until the
              # last non-opaque entry. Set up an array, stretching over all
              # palette entries which will be 0 (opaque) or 1 (transparent).
            trans[:type]  = 'indexed'
            trans[:data]  = data.read_o(chunk_size).unpack("C*")
          when 0
              # Greyscale. Corresponding to entries in the PLTE chunk.
              # Grey is two bytes, range 0 .. (2 ^ bit-depth) - 1
            trans[:grayscale] = data.read_o(2).unpack("n")
            trans[:type]      = 'indexed'
            trans[:data]      = data.read_o.unpack("C")
          when 2
              # True colour with proper alpha channel.
            trans[:rgb] = data.read_o(6).unpack("nnn")
          end
        else
          data.offset += chunk_size
        end

        ok = section != "IEND"

        data.read_o(4)  # Skip the CRC
      end

      if image.bits > 8
        raise TypeError, PDF::Writer::Message[:png_8bit_colour]
      end
      if image.info[:interlace_method] != 0
        raise TypeError, PDF::Writer::Message[:png_interlace]
      end

      ncolor  = 1
      colour  = 'DeviceRGB'
      case image.info[:color_type]
      when 3
        nil
      when 2
        ncolor = 3
      when 0
        colour = 'DeviceGray'
      else
        raise TypeError, PDF::Writer::Message[:png_alpha_trans]
      end

      @info['Filter'] = '[/FlateDecode]'
      @info['DecodeParms'] = "[<</Predictor 15 /Colors #{ncolor} /Columns #{image.width}>>]"
      @info['BitsPerComponent'] = image.bits.to_s

      unless palette.empty?
        @info['ColorSpace']  = " [ /Indexed /DeviceRGB #{(palette.size / 3) - 1} "
        contents            = PDF::Writer::Contents.new
        contents.data       = palette
        @info['ColorSpace'] << "#{contents.oid} 0 R ]"

        if trans
          case trans[:type]
          when 'indexed'
            @info['Mask']   = " [ #{trans[:data].join(' ')} ] "
          end
        end
      else
        @info['ColorSpace'] = "/#{colour}"
      end

      @data = idat
    end

    @label = label

      # assign it a place in the named resource dictionary as an external
      # object, according to the label passed in with it.
    @parent.pages << self
      # also make sure that we have the right procset object for it.
    @parent.procset << 'ImageC'
  end

  def to_s
    tmp = @data.dup
    res = "\n#{@oid} 0 obj\n<<"
    @info.each { |k, v| res << "\n/#{k} #{v}"}
    if (@parent.encrypted?)
      @parent.arc4.prepare(self)
      tmp = @parent.arc4.encrypt(tmp)
    end
    res << "\n/Length #{tmp.size} >>\nstream\n#{tmp}\nendstream\nendobj\n"
    res
  end
end