xobject.rb

=begin

    This file is part of Origami, PDF manipulation framework for Ruby
    Copyright (C) 2016	Guillaume Delugré.

    Origami is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Origami is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with Origami.  If not, see <http://www.gnu.org/licenses/>.

=end

module Origami

    #
    # A class representing a Stream containing the contents of a Page.
    #
    class ContentStream < Stream

        DEFAULT_SIZE = 12
        DEFAULT_FONT = :F1
        DEFAULT_LEADING = 20
        DEFAULT_STROKE_COLOR = Graphics::Color::GrayScale.new(0.0)
        DEFAULT_FILL_COLOR = Graphics::Color::GrayScale.new(1.0)
        DEFAULT_LINECAP = Graphics::LineCapStyle::BUTT_CAP
        DEFAULT_LINEJOIN = Graphics::LineJoinStyle::MITER_JOIN
        DEFAULT_DASHPATTERN = Graphics::DashPattern.new([], 0)
        DEFAULT_LINEWIDTH = 1.0

        attr_accessor :canvas

        def initialize(data = "", dictionary = {})
            super

            @instructions = nil
            @canvas = Graphics::DummyCanvas.new
        end

        def render(engine)
            load!

            @instructions.each do |instruction|
                instruction.render(engine)
            end

            nil
        end

        def pre_build #:nodoc:
            unless @instructions.nil?
                if @canvas.gs.text_state.is_in_text_object?
                    @instructions << PDF::Instruction.new('ET').render(@canvas)
                end

                @data = @instructions.join
            end

            super
        end

        def instructions
            load!

            @instructions
        end

        def draw_image(name, attr = {})
            load!

            x, y = attr[:x], attr[:y]

            @instructions << PDF::Instruction.new('q')
            @instructions << PDF::Instruction.new('cm', 300, 0, 0, 300, x, y)
            @instructions << PDF::Instruction.new('Do', name)
            @instructions << PDF::Instruction.new('Q')
        end

        #
        # Draw a straight line from the point at coord _from_, to the point at coord _to_.
        #
        def draw_line(from, to, attr = {})
            draw_polygon([from, to], attr)
        end

        #
        # Draw a polygon from a array of coordinates.
        #
        def draw_polygon(coords = [], attr = {})
            load!

            stroke_color  = attr.fetch(:stroke_color, DEFAULT_STROKE_COLOR)
            fill_color    = attr.fetch(:fill_color, DEFAULT_FILL_COLOR)
            line_cap      = attr.fetch(:line_cap, DEFAULT_LINECAP)
            line_join     = attr.fetch(:line_join, DEFAULT_LINEJOIN)
            line_width    = attr.fetch(:line_width, DEFAULT_LINEWIDTH)
            dash_pattern  = attr.fetch(:dash, DEFAULT_DASHPATTERN)

            stroke        = attr[:stroke].nil? ? true : attr[:stroke]
            fill          = attr[:fill].nil? ? false : attr[:fill]

            stroke = true if fill == false and stroke == false

            set_fill_color(fill_color) if fill
            set_stroke_color(stroke_color) if stroke
            set_line_width(line_width)
            set_line_cap(line_cap)
            set_line_join(line_join)
            set_dash_pattern(dash_pattern)

            if @canvas.gs.text_state.is_in_text_object?
                @instructions << PDF::Instruction.new('ET').render(@canvas)
            end

            unless coords.size < 1
                x,y = coords.slice!(0)
                @instructions << PDF::Instruction.new('m',x,y).render(@canvas)

                coords.each do |px,py|
                    @instructions << PDF::Instruction.new('l',px,py).render(@canvas)
                end

                @instructions << (i =
                    if stroke and not fill
                        PDF::Instruction.new('s')
                    elsif fill and not stroke
                        PDF::Instruction.new('f')
                    elsif fill and stroke
                        PDF::Instruction.new('b')
                    end
                )

                i.render(@canvas)
            end

            self
        end

        #
        # Draw a rectangle at position (_x_,_y_) with defined _width_ and _height_.
        #
        def draw_rectangle(x, y, width, height, attr = {})
            load!

            stroke_color  = attr.fetch(:stroke_color, DEFAULT_STROKE_COLOR)
            fill_color    = attr.fetch(:fill_color, DEFAULT_FILL_COLOR)
            line_cap      = attr.fetch(:line_cap, DEFAULT_LINECAP)
            line_join     = attr.fetch(:line_join, DEFAULT_LINEJOIN)
            line_width    = attr.fetch(:line_width, DEFAULT_LINEWIDTH)
            dash_pattern  = attr.fetch(:dash, DEFAULT_DASHPATTERN)

            stroke        = attr[:stroke].nil? ? true : attr[:stroke]
            fill          = attr[:fill].nil? ? false : attr[:fill]

            stroke = true if fill == false and stroke == false

            set_fill_color(fill_color) if fill
            set_stroke_color(stroke_color) if stroke
            set_line_width(line_width)
            set_line_cap(line_cap)
            set_line_join(line_join)
            set_dash_pattern(dash_pattern)

            if @canvas.gs.text_state.is_in_text_object?
                @instructions << PDF::Instruction.new('ET').render(@canvas)
            end

            @instructions << PDF::Instruction.new('re', x,y,width,height).render(@canvas)

            @instructions << (i =
                if stroke and not fill
                    PDF::Instruction.new('S')
                elsif fill and not stroke
                    PDF::Instruction.new('f')
                elsif fill and stroke
                    PDF::Instruction.new('B')
                end
            )

            i.render(@canvas)

            self
        end

        #
        # Adds text to the content stream with custom formatting attributes.
        # _text_:: Text to write.
        # _attr_:: Formatting attributes.
        #
        def write(text, attr = {})
            load!

            x, y      = attr[:x], attr[:y]
            font      = attr.fetch(:font, DEFAULT_FONT)
            size      = attr.fetch(:size, DEFAULT_SIZE)
            leading   = attr.fetch(:leading, DEFAULT_LEADING)
            color     = attr.fetch(:color, attr.fetch(:fill_color, DEFAULT_STROKE_COLOR))
            stroke_color = attr.fetch(:stroke_color, DEFAULT_STROKE_COLOR)
            line_width    = attr.fetch(:line_width, DEFAULT_LINEWIDTH)
            word_spacing  = attr.fetch(:word_spacing, @canvas.gs.text_state.word_spacing)
            char_spacing  = attr.fetch(:char_spacing, @canvas.gs.text_state.char_spacing)
            scale     = attr.fetch(:scale, @canvas.gs.text_state.scaling)
            rise      = attr.fetch(:rise, @canvas.gs.text_state.text_rise)
            rendering = attr.fetch(:rendering, @canvas.gs.text_state.rendering_mode)

            @instructions << PDF::Instruction.new('ET').render(@canvas) if (x or y) and @canvas.gs.text_state.is_in_text_object?

            unless @canvas.gs.text_state.is_in_text_object?
                @instructions << PDF::Instruction.new('BT').render(@canvas)
            end

            set_text_font(font, size)
            set_text_pos(x, y) if x or y
            set_text_leading(leading)
            set_text_rendering(rendering)
            set_text_rise(rise)
            set_text_scale(scale)
            set_text_word_spacing(word_spacing)
            set_text_char_spacing(char_spacing)
            set_fill_color(color)
            set_stroke_color(stroke_color)
            set_line_width(line_width)

            write_text_block(text)

            self
        end

        def paint_shading(shade)
            load!

            @instructions << PDF::Instruction.new('sh', shade).render(@canvas)

            self
        end

        def set_text_font(fontname, size)
            load!

            if fontname != @canvas.gs.text_state.font or size != @canvas.gs.text_state.font_size
                @instructions << PDF::Instruction.new('Tf', fontname, size).render(@canvas)
            end

            self
        end

        def set_text_pos(tx,ty)
            load!

            @instructions << PDF::Instruction.new('Td', tx, ty).render(@canvas)

            self
        end

        def set_text_leading(leading)
            load!

            if leading != @canvas.gs.text_state.leading
                @instructions << PDF::Instruction.new('TL', leading).render(@canvas)
            end

            self
        end

        def set_text_rendering(rendering)
            load!

            if rendering != @canvas.gs.text_state.rendering_mode
                @instructions << PDF::Instruction.new('Tr', rendering).render(@canvas)
            end

            self
        end

        def set_text_rise(rise)
            load!

            if rise != @canvas.gs.text_state.text_rise
                @instructions << PDF::Instruction.new('Ts', rise).render(@canvas)
            end

            self
        end

        def set_text_scale(scaling)
            load!

            if scaling != @canvas.gs.text_state.scaling
                @instructions << PDF::Instruction.new('Tz', scaling).render(@canvas)
            end

            self
        end

        def set_text_word_spacing(word_spacing)
            load!

            if word_spacing != @canvas.gs.text_state.word_spacing
                @instructions << PDF::Instruction.new('Tw', word_spacing).render(@canvas)
            end

            self
        end

        def set_text_char_spacing(char_spacing)
            load!

            if char_spacing != @canvas.gs.text_state.char_spacing
                @instructions << PDF::Instruction.new('Tc', char_spacing).render(@canvas)
            end

            self
        end

        def set_fill_color(color)
            load!

            @instructions << ( i =
                if (color.respond_to? :r and color.respond_to? :g and color.respond_to? :b) or (color.is_a?(::Array) and color.size == 3)
                    r = (color.respond_to?(:r) ? color.r : color[0]).to_f / 255
                    g = (color.respond_to?(:g) ? color.g : color[1]).to_f / 255
                    b = (color.respond_to?(:b) ? color.b : color[2]).to_f / 255
                    PDF::Instruction.new('rg', r, g, b) if @canvas.gs.nonstroking_color != [r,g,b]

                elsif (color.respond_to? :c and color.respond_to? :m and color.respond_to? :y and color.respond_to? :k) or (color.is_a?(::Array) and color.size == 4)
                    c = (color.respond_to?(:c) ? color.c : color[0]).to_f
                    m = (color.respond_to?(:m) ? color.m : color[1]).to_f
                    y = (color.respond_to?(:y) ? color.y : color[2]).to_f
                    k = (color.respond_to?(:k) ? color.k : color[3]).to_f
                    PDF::Instruction.new('k', c, m, y, k) if @canvas.gs.nonstroking_color != [c,m,y,k]

                elsif color.respond_to?:g or (0.0..1.0) === color
                    g = color.respond_to?(:g) ? color.g : color
                    PDF::Instruction.new('g', g) if @canvas.gs.nonstroking_color != [ g ]

                else
                    raise TypeError, "Invalid color : #{color}"
                end
            )

            i.render(@canvas) if i
            self
        end

        def set_stroke_color(color)
            load!

            @instructions << ( i =
                if (color.respond_to? :r and color.respond_to? :g and color.respond_to? :b) or (color.is_a?(::Array) and color.size == 3)
                    r = (color.respond_to?(:r) ? color.r : color[0]).to_f / 255
                    g = (color.respond_to?(:g) ? color.g : color[1]).to_f / 255
                    b = (color.respond_to?(:b) ? color.b : color[2]).to_f / 255
                    PDF::Instruction.new('RG', r, g, b) if @canvas.gs.stroking_color != [r,g,b]

                elsif (color.respond_to? :c and color.respond_to? :m and color.respond_to? :y and color.respond_to? :k) or (color.is_a?(::Array) and color.size == 4)
                    c = (color.respond_to?(:c) ? color.c : color[0]).to_f
                    m = (color.respond_to?(:m) ? color.m : color[1]).to_f
                    y = (color.respond_to?(:y) ? color.y : color[2]).to_f
                    k = (color.respond_to?(:k) ? color.k : color[3]).to_f
                    PDF::Instruction.new('K', c, m, y, k) if @canvas.gs.stroking_color != [c,m,y,k]

                elsif color.respond_to?:g or (0.0..1.0) === color
                    g = color.respond_to?(:g) ? color.g : color
                    PDF::Instruction.new('G', g) if @canvas.gs.stroking_color != [ g ]

                else
                    raise TypeError, "Invalid color : #{color}"
                end
            )

            i.render(@canvas) if i
            self
        end

        def set_dash_pattern(pattern)
            load!

            unless @canvas.gs.dash_pattern.eql? pattern
                @instructions << PDF::Instruction.new('d', pattern.array, pattern.phase).render(@canvas)
            end

            self
        end

        def set_line_width(width)
            load!

            if @canvas.gs.line_width != width
                @instructions << PDF::Instruction.new('w', width).render(@canvas)
            end

            self
        end

        def set_line_cap(cap)
            load!

            if @canvas.gs.line_cap != cap
                @instructions << PDF::Instruction.new('J', cap).render(@canvas)
            end

            self
        end

        def set_line_join(join)
            load!

            if @canvas.gs.line_join != join
                @instructions << PDF::Instruction.new('j', join).render(@canvas)
            end

            self
        end

        private

        def load!
            return unless @instructions.nil?

            decode!

            code = StringScanner.new self.data
            @instructions = []

            until code.eos?
                insn = PDF::Instruction.parse(code)
                @instructions << insn if insn
            end

            self
        end

        def write_text_block(text)
            lines = text.split("\n").map!{|line| line.to_s}

            @instructions << PDF::Instruction.new('Tj', lines.slice!(0)).render(@canvas)
            lines.each do |line|
                @instructions << PDF::Instruction.new("'", line).render(@canvas)
            end
        end
    end #class ContentStream

    class Page < Dictionary

        def render(engine) #:nodoc:
            contents = self.Contents
            contents = [ contents ] unless contents.is_a? Array

            contents.each do |stream|
                stream = stream.cast_to(ContentStream) unless stream.is_a? ContentStream

                stream.render(engine)
            end
        end

        # TODO :nodoc:
        def draw_image
            raise NotImplementedError
        end

        # See ContentStream#draw_line.
        def draw_line(from, to, attr = {})
            last_content_stream.draw_line(from, to, attr); self
        end

        # See ContentStream#draw_polygon.
        def draw_polygon(coords = [], attr = {})
            last_content_stream.draw_polygon(coords, attr); self
        end

        # See ContentStream#draw_rectangle.
        def draw_rectangle(x, y, width, height, attr = {})
            last_content_stream.draw_rectangle(x, y, width, height, attr); self
        end

        # See ContentStream#write.
        def write(text, attr = {})
            last_content_stream.write(text, attr); self
        end

        # TODO :nodoc:
        def paint_shading(_shade)
            raise NotImplementedError
        end

        # TODO :nodoc:
        def set_text_font(_font, _size)
            raise NotImplementedError
        end

        # See ContentStream#set_text_pos.
        def set_text_pos(tx, ty)
            last_content_stream.set_text_pos(tx, ty); self
        end

        # See ContentStream#set_text_leading.
        def set_text_leading(leading)
            last_content_stream.set_text_leading(leading); self
        end

        # See ContentStream#set_text_rendering.
        def set_text_rendering(rendering)
            last_content_stream.set_text_rendering(rendering); self
        end

        # See ContentStream#set_text_rise.
        def set_text_rise(rise)
            last_content_stream.set_text_rise(rise); self
        end

        # See ContentStream#set_text_scale.
        def set_text_scale(scaling)
            last_content_stream.set_text_scale(scaling); self
        end

        # See ContentStream#set_text_word_spacing.
        def set_text_word_spacing(word_spacing)
            last_content_stream.set_text_word_spacing(word_spacing); self
        end

        # See ContentStream#set_text_char_spacing.
        def set_text_char_spacing(char_spacing)
            last_content_stream.set_text_char_spacing(char_spacing); self
        end

        # See ContentStream#set_fill_color.
        def set_fill_color(color)
            last_content_stream.set_fill_color(color); self
        end

        # See ContentStream#set_stroke_color.
        def set_stroke_color(color)
            last_content_stream.set_stroke_color(color); self
        end

        # See ContentStream#set_dash_pattern.
        def set_dash_pattern(pattern)
            last_content_stream.set_dash_pattern(pattern); self
        end

        # See ContentStream#set_line_width.
        def set_line_width(width)
            last_content_stream.set_line_width(width); self
        end

        # See ContentStream#set_line_cap.
        def set_line_cap(cap)
            last_content_stream.set_line_cap(cap); self
        end

        # See ContentStream#set_line_join.
        def set_line_join(join)
            last_content_stream.set_line_join(join); self
        end

        private

        def last_content_stream #:nodoc:
            streams = self.content_streams
            if streams.empty?
                self.Contents = ContentStream.new
            else
                streams.last
            end
        end
    end # class Page

    module Graphics

        module XObject
            def self.included(receiver)
                receiver.field  :Type,    :Type => Name, :Default => :XObject
            end
        end

        class FormXObject < ContentStream
            include XObject
            include ResourcesHolder

            class Group < Dictionary
                include StandardObject

                module Type
                    TRANSPARENCY = :Transparency
                end

                field   :Type,      :Type => Name, :Default => :Group
                field   :S,         :Type => Name, :Default => Type::TRANSPARENCY, :Required => true
            end

            class Reference < Dictionary
                include StandardObject

                field   :F,         :Type => FileSpec, :Required => true
                field   :Page,      :Type => [ Integer, String ], :Required => true
                field   :ID,        :Type => Array.of(String, length: 2)
            end

            field   :Subtype,       :Type => Name, :Default => :Form, :Required => true
            field   :FormType,      :Type => Integer, :Default => 1
            field   :BBox,          :Type => Rectangle, :Required => true
            field   :Matrix,        :Type => Array.of(Number, length: 6), :Default => [1, 0, 0, 1, 0, 0]
            field   :Resources,     :Type => Resources, :Version => "1.2"
            field   :Group,         :Type => Group, :Version => "1.4"
            field   :Ref,           :Type => Reference, :Version => "1.4"
            field   :Metadata,      :Type => MetadataStream, :Version => "1.4"
            field   :PieceInfo,     :Type => Dictionary, :Version => "1.3"
            field   :LastModified,  :Type => String, :Version => "1.3"
            field   :StructParent,  :Type => Integer, :Version => "1.3"
            field   :StructParents, :Type => Integer, :Version => "1.3"
            field   :OPI,           :Type => Dictionary, :Version => "1.2"
            field   :OC,            :Type => Dictionary, :Version => "1.5"
            field   :Name,          :Type => Name
            field   :Measure,       :Type => Dictionary, :Version => "1.7", :ExtensionLevel => 3
            field   :PtData,        :Type => Dictionary, :Version => "1.7", :ExtensionLevel => 3

            def pre_build
                self.Resources = Resources.new.pre_build unless self.key?(:Resources)

                super
            end
        end

        class ImageXObject < Stream
            include XObject

            field   :Subtype,           :Type => Name, :Default => :Image, :Required => true
            field   :Width,             :Type => Integer, :Required => true
            field   :Height,            :Type => Integer, :Required => true
            field   :ColorSpace,        :Type => [ Name, Array ]
            field   :BitsPerComponent,  :Type => Integer
            field   :Intent,            :Type => Name, :Version => "1.1"
            field   :ImageMask,         :Type => Boolean, :Default => false
            field   :Mask,              :Type => [ ImageXObject, Array.of(Integer) ], :Version => "1.3"
            field   :Decode,            :Type => Array.of(Number)
            field   :Interpolate,       :Type => Boolean, :Default => false
            field   :Alternates,        :Type => Array, :Version => "1.3"
            field   :SMask,             :Type => ImageXObject, :Version => "1.4"
            field   :SMaskInData,       :Type => Integer, :Default => 0, :Version => "1.5"
            field   :Name,              :Type => Name
            field   :StructParent,      :Type => Integer, :Version => "1.3"
            field   :ID,                :Type => String, :Version => "1.3"
            field   :OPI,               :Type => Dictionary, :Version => "1.2"
            field   :Matte,             :Type => Array.of(Number), :Version => "1.4" # Used in Soft-Mask images.
            field   :Metadata,          :Type => MetadataStream, :Version => "1.4"
            field   :OC,                :Type => Dictionary, :Version => "1.5"
            field   :Measure,           :Type => Dictionary, :Version => "1.7", :ExtensionLevel => 3
            field   :PtData,            :Type => Dictionary, :Version => "1.7", :ExtensionLevel => 3

            def self.from_image_file(path, format = nil)
                if path.respond_to?(:read)
                    data = fd.read
                else
                    data = File.binread(File.expand_path(path))
                    format ||= File.extname(path)
                end

                image = ImageXObject.new

                raise ArgumentError, "Missing file format" if format.nil?
                case format.downcase
                when 'jpg', 'jpeg', 'jpe', 'jif', 'jfif', 'jfi'
                    image.setFilter :DCTDecode
                    image.encoded_data = data

                when 'jp2','jpx','j2k','jpf','jpm','mj2'
                    image.setFilter :JPXDecode
                    image.encoded_data = data

                when 'jb2', 'jbig', 'jbig2'
                    image.setFilter :JBIG2Decode
                    image.encoded_data = data
                else
                    raise NotImplementedError, "Unknown file format: '#{format}'"
                end

                image
            end

            #
            # Converts an ImageXObject stream into an image file data.
            # Output format depends on the stream encoding:
            #   * JPEG for DCTDecode
            #   * JPEG2000 for JPXDecode
            #   * JBIG2 for JBIG2Decode
            #   * PNG for everything else
            #
            #   Returns an array of the form [ _format_, _data_ ]
            #
            def to_image_file
                encoding = self.Filter
                encoding = encoding[0] if encoding.is_a? ::Array

                case (encoding && encoding.value)
                when :DCTDecode then return [ 'jpg', self.data ]
                when :JBIG2Decode then return [ 'jbig2', self.data ]
                when :JPXDecode then return [ 'jp2', self.data ]
                end

                # Assume PNG data.

                raise InvalidColorError, "No colorspace specified" unless self.ColorSpace

                case cs = self.ColorSpace.value
                when Color::Space::DEVICE_GRAY
                    color_type = 0
                    components = 1
                when Color::Space::DEVICE_RGB
                    color_type = 2
                    components = 3
                when ::Array
                    cs_type = cs[0]
                    case cs_type
                    when :Indexed
                        color_type = 3
                        components = 3
                        cs_base = cs[1]
                        lookup = cs[3]

                    when :ICCBased
                        icc_profile = cs[1]
                        raise InvalidColorError,
                                "Invalid ICC Profile parameter" unless icc_profile.is_a?(Stream)

                        case icc_profile.N
                        when 1
                            color_type = 0
                            components = 1
                        when 3
                            color_type = 2
                            components = 3
                        else
                            raise InvalidColorError,
                                    "Invalid number of components in ICC profile: #{icc_profile.N}"
                        end
                    else
                        raise InvalidColorError, "Unsupported color space: #{self.ColorSpace}"
                    end
                else
                    raise InvalidColorError, "Unsupported color space: #{self.ColorSpace}"
                end

                bpc = self.BitsPerComponent || 8
                w, h = self.Width, self.Height
                pixels = self.data

                hdr = [137, 80, 78, 71, 13, 10, 26, 10].pack('C*')
                chunks = []

                chunks <<
                [
                    'IHDR',
                    [
                        w, h,
                        bpc, color_type, 0, 0, 0
                    ].pack("N2C5")
                ]


                if self.Intents
                    intents =
                        case self.Intents.value
                        when Intents::PERCEPTUAL then 0
                        when Intents::RELATIVE then 1
                        when Intents::SATURATION then 2
                        when Intents::ABSOLUTE then 3
                        else
                            3
                        end

                    chunks <<
                    [
                        'sRGB',
                        [ intents ].pack('C')
                    ]

                    chunks << [ 'gAMA', [ 45455 ].pack("N") ]
                    chunks <<
                    [
                        'cHRM',
                        [
                            31270,
                            32900,
                            64000,
                            33000,
                            30000,
                            60000,
                            15000,
                            6000
                        ].pack("N8")
                    ]
                end

                if color_type == 3
                    lookup =
                        case lookup
                        when Stream then lookup.data
                        when String then lookup.value
                        else
                            raise InvalidColorError, "Invalid indexed palette table"
                        end

                    raise InvalidColorError, "Invalid base color space" unless cs_base
                    palette = ""

                    case cs_base
                    when Color::Space::DEVICE_GRAY
                        lookup.each_byte do |g|
                            palette << Color.gray_to_rgb(g).pack("C3")
                        end
                    when Color::Space::DEVICE_RGB
                        palette << lookup[0, (lookup.size / 3) * 3]

                    when Color::Space::DEVICE_CMYK
                        (lookup.size / 4).times do |i|
                            cmyk = lookup[i * 4, 4].unpack("C4").map!{|c| c.to_f / 255}
                            palette << Color.cmyk_to_rgb(*cmyk).map!{|c| (c * 255).to_i}.pack("C3")
                        end
                    when ::Array

                        case cs_base[0]
                        when :ICCBased
                            icc_profile = cs_base[1]
                            raise InvalidColorError,
                                    "Invalid ICC Profile parameter" unless icc_profile.is_a?(Stream)

                            case icc_profile.N
                            when 1
                                lookup.each_byte do |g|
                                    palette << Color.gray_to_rgb(g).pack("C3")
                                end
                            when 3
                                palette << lookup[0, (lookup.size / 3) * 3]
                            else
                                raise InvalidColorError,
                                        "Invalid number of components in ICC profile: #{icc_profile.N}"
                            end
                        else
                            raise InvalidColorError, "Unsupported color space: #{cs_base}"
                        end
                    else
                        raise InvalidColorError, "Unsupported color space: #{cs_base}"
                    end

                    if icc_profile
                        chunks <<
                        [
                            'iCCP',
                            'ICC Profile' + "\x00\x00" + Zlib::Deflate.deflate(icc_profile.data, Zlib::BEST_COMPRESSION)
                        ]
                    end

                    chunks <<
                    [
                        'PLTE',
                        palette
                    ]

                    bpr = w

                else # color_type != 3
                    if icc_profile
                        chunks <<
                        [
                            'iCCP',
                            'ICC Profile' + "\x00\x00" + Zlib::Deflate.deflate(icc_profile.data, Zlib::BEST_COMPRESSION)
                        ]
                    end

                    bpr = (bpc >> 3) * components * w
                end

                nrows = pixels.size / bpr
                nrows.times do |irow|
                    pixels.insert(irow * bpr + irow, "\x00")
                end

                chunks <<
                [
                    'IDAT',
                     Zlib::Deflate.deflate(pixels, Zlib::BEST_COMPRESSION)
                ]

                if self.Metadata.is_a?(Stream)
                    chunks <<
                    [
                        'tEXt',
                        "XML:com.adobe.xmp" + "\x00" + self.Metadata.data
                    ]
                end

                chunks << [ 'IEND', '' ]

                [ 'png',
                    hdr + chunks.map!{ |chk|
                        [ chk[1].size, chk[0], chk[1], Zlib.crc32(chk[0] + chk[1]) ].pack("NA4A*N")
                    }.join
                ]
            end
        end

        class ReferenceDictionary < Dictionary
            include StandardObject

            field   :F,             :Type => Dictionary, :Required => true
            field   :Page,          :Type => [Integer, String], :Required => true
            field   :ID,            :Tyoe => Array
        end
    end

end