=begin

= gifcat.rb

gifcat.rb is a library for concatenation of gif images.

== version
v0.0.1  2002/09/18  initial version.

== License

Copyright (c) 2002  TAKAHASHI 'Maki' Masayoshi
(Original version) Copyright (c) 1997,2002 http://tohoho.wakusei.ne.jp/

This library is free software; you can use, copy, modify
and re-distribute it with above copyright notices and this
permission notice.

== Original Header

;# ====================================================================
;#
;# gifcat.pl: GIFファイル連結ライブラリ Ver1.61
;#
;# Copyright (c) 1997,2002 http://tohoho.wakusei.ne.jp/
;#
;# 著作権は放棄しませんが、自由に使用・改造・再配布可能です。
;#
;# 基本的な使い方
(略)
;# 制限事項
;#    アニメGIF同士を連結することはできません。
;#    アニメGIF対応のブラウザでなければ、最初の画像しか表示されません。
;#    高さの異なるGIFファイルは連結できません。
;#
;# 最新版入手先
;#    http://tohoho.wakusei.ne.jp/wwwsoft.htm
;#
;# 更新履歴:
(略)
;#
;# ====================================================================
=end


class GIFCat

  attr_accessor :debug

  def initialize()
    @debug = nil
  end

  ##
  # get a concatenated GIF image.
  #
  def read_files(*files)
    @data = []
    @gif = 0
    @logicalScreenWidth = 0
    @logicalScreenHeight = 0
    @useLocalColorTable = 0
    @packedFields18 = []
    @packedFields20 = []
    @packedFields23 = []
    @globalColorTable= []
    @transparentColorFlag = []
    @transparentColorIndex = []
    @imageWidth = []
    @imageHeight = 0
    @lzwMinimumCodeSize = []
    @imageData = []

    files.each{|file|
      begin
	File.open(file,"rb"){|f|
	  @buf = f.read()
	}
	size = @buf.size
      rescue
	raise "ERROR"
      end

      @cnt = 0
      header()
      loop do
	x1 = @buf[@cnt]

	if x1 == 0x2c
	  image_block()
	elsif x1 == 0x21
	  x2 = @buf[@cnt+1]

	  case x2
	  when 0xf9
	    graphic_control_extension()
	  when 0xfe
	    comment_extension()
	  when 0x01
	    plaintext_extension()
	  when 0xff
	    application_extension();
	  else
	    raise "ERROR"
	  end
	elsif x1 == 0x3b
	  trailer()
	  break
	elsif @cnt == size
	  break
	else
	  raise "ERROR"
	end
      end

      @buf = nil
      @gif += 1
    }
  end

  def to_gif
    if @gif < 1
      raise "no data"
    end

    gifImage = "GIF89a"   # signature and version
    gifImage +=
      [@logicalScreenWidth & 0x00ff,
       (@logicalScreenWidth & 0xff00) >> 8,
       @logicalScreenHeight & 0x00ff,
       (@logicalScreenHeight & 0xff00) >> 8].pack("CCCC")

    if @useLocalColorTable != 0
      @packedFields18[0] &= ~0x80
    end

    gifImage += [@packedFields18[0]].pack("C")
    gifImage += [@backgroundColorIndex].pack("C")
    gifImage += [@pixelAspectRatio].pack("C")
    if @useLocalColorTable == 0
      gifImage += @globalColorTable[0]
    end

#    i = -1
    i = 0
    leftpos = 0;
    while (i < @gif)
#      j = (i == -1) ? 0 : i
      j = i
      gifImage += [0x21, 0xf9, 0x04].pack("CCC")
      gifImage += [@packedFields23 | @transparentColorFlag[j]].pack("C")
      gifImage += [0x00, 0x00].pack("CC");
      gifImage += [@transparentColorIndex[j]].pack("C")
      gifImage += [0x00].pack("C")

      gifImage += [0x2c].pack("C")  # image block
      n = leftpos
#      leftpos += (i == -1) ? 0 : @imageWidth[j]
      leftpos += @imageWidth[j]
      gifImage += [n & 0x00ff].pack("C");
      gifImage += [(n & 0xff00) >> 8].pack("C");
      gifImage += [0x00, 0x00].pack("CC");
      gifImage += [@imageWidth[j] & 0x00ff].pack("C")
      gifImage += [(@imageWidth[j] & 0xff00) >> 8].pack("C")
      gifImage += [@imageHeight & 0x00ff].pack("C")
      gifImage += [(@imageHeight & 0xff00) >> 8].pack("C")
      if @useLocalColorTable != 0
	@packedFields20[j] |= 0x80;
	@packedFields20[j] &= ~0x07;
	@packedFields20[j] |= (@packedFields18[j] & 0x07)
	gifImage += [@packedFields20[j]].pack("C")
	gifImage += @globalColorTable[j]
      else 
	gifImage += [@packedFields20[j]].pack("C")
      end
      gifImage += [@lzwMinimumCodeSize[j]].pack("C")
      gifImage += @imageData[j]
      
      i += 1
    end
    gifImage += [0x3b].pack("C")

    return gifImage
  end

  ##
  # GifHeader
  #
  def header()
    signature = @buf[@cnt, 3]
    version   = @buf[@cnt+3, 3]
    logicalScreenWidth = @buf[@cnt+6] + @buf[@cnt+7]*256
    logicalScreenHeight = @buf[@cnt+8] + @buf[@cnt+9]*256
    @packedFields18[@gif] = @buf[@cnt+10]
    globalColorTableFlag = (@packedFields18[@gif] & 0x80) >> 7
    colorResolution      = ((@packedFields18[@gif] & 0x70) >> 4) + 1
    sortFlag             = (@packedFields18[@gif] & 0x08) >> 3
    sizeOfGlobalColorTable = 2 ** ((@packedFields18[@gif] & 0x07) + 1)
    @backgroundColorIndex   = @buf[@cnt+11]
    @pixelAspectRatio       = @buf[@cnt+12]
    @cnt += 13

    if globalColorTableFlag != 0
      globalColorTable = @buf[@cnt, sizeOfGlobalColorTable * 3]
      @cnt += sizeOfGlobalColorTable * 3
    else
      globalColorTable = ""
    end

    @logicalScreenWidth += logicalScreenWidth
    if @logicalScreenHeight < logicalScreenHeight
      @logicalScreenHeight = logicalScreenHeight
    end
    if globalColorTableFlag != 0
      @globalColorTable[@gif] = globalColorTable
      if @gif > 0
	if globalColorTable != @globalColorTable[@gif - 1]
	  @useLocalColorTable = 1
	end
      end
    end

    if @debug
      printf "=====================================\n"
      printf "GifHeader\n"
      printf "=====================================\n"
      printf "Signature:                     %s\n", signature
      printf "Version:                       %s\n", version
      printf "Logical Screen Width:          %d\n", logicalScreenWidth
      printf "Logical Screen Height:         %d\n", logicalScreenHeight
      printf "Global Color Table Flag:       %d\n", globalColorTableFlag
      printf "Color Resolution:              %d\n", colorResolution
      printf "Sort Flag:                     %d\n", sortFlag
      printf "Size of Global Color Table:    %d * 3\n",
	sizeOfGlobalColorTable
      printf "Background Color Index:        %d\n", @backgroundColorIndex
      printf "Pixel Aspect Ratio:            %d\n", @pixelAspectRatio
      printf "Global Color Table:            \n"
      dump(globalColorTable)
    end
  end

  ##
  # Image Block
  #
  def image_block
    imageSeparator    = @buf[@cnt]
    imageLeftPosition = @buf[@cnt+1] + @buf[@cnt+2]*256
    imageTopPosition  = @buf[@cnt+3] + @buf[@cnt+4]*256
    @imageWidth[@gif]  = @buf[@cnt+5] + @buf[@cnt+6]*256
    @imageHeight       = @buf[@cnt+7] + @buf[@cnt+8]*256
    @packedFields20[@gif] = @buf[@cnt+9]
    @cnt += 10
    localColorTableFlag   = (@packedFields20[@gif] & 0x80) >> 7
    interlaceFlag         = (@packedFields20[@gif] & 0x40) >> 6
    sortFlag              = (@packedFields20[@gif] & 0x20) >> 5
    reserved              = (@packedFields20[@gif] & 0x18) >> 3
    if localColorTableFlag != 0
      sizeOfLocalColorTable = 2 ** ((@packedFields20[@gif] & 0x07) + 1)
      localColorTable = @buf[@cnt, sizeOfLocalColorTable * 3]
      @cnt += sizeOfLocalColorTable * 3
    else
      sizeOfLocalColorTable = 0
      localColorTable = ""
    end
    @lzwMinimumCodeSize[@gif] = @buf[@cnt]
    @cnt += 1
    @imageData[@gif] = dataSubBlock()

    if @debug
      printf "=====================================\n"
      printf "Image Block\n"
      printf "=====================================\n"
      printf "Image Separator:               0x%02x\n", imageSeparator
      printf "Image Left Position:           %d\n", imageLeftPosition
      printf "Image Top Position:            %d\n", imageTopPosition
      printf "Image Width:                   %d\n", @imageWidth[@gif]
      printf "Image Height:                  %d\n", @imageHeight
      printf "Local Color Table Flag:        %d\n", localColorTableFlag
      printf "Interlace Flag:                %d\n", interlaceFlag
      printf "Sort Flag:                     %d\n", sortFlag
      printf "Reserved:                      --\n"
      printf "Size of Local Color Table:     %d\n", sizeOfLocalColorTable
      printf "Local Color Table:             \n"
      dump(localColorTable)
      printf "LZW Minimum Code Size:         %d\n", @lzwMinimumCodeSize[@gif]
      printf "Image Data:                    \n"
      dump(@imageData[@gif])
      printf "Block Terminator:              0x00\n"
    end
  end

  ##
  # Graphic Control Extension
  #
  def graphic_control_extension
    extensionIntroducer   = @buf[@cnt]
    graphicControlLabel   = @buf[@cnt+1]
    blockSize             = @buf[@cnt+2]
    @packedFields23        = @buf[@cnt+3]
    reserved              = (@packedFields23 & 0xe0) >> 5
    disposalMethod        = (@packedFields23 & 0x1c) >> 5
    userInputFlag         = (@packedFields23 & 0x02) >> 1
    @transparentColorFlag[@gif]  = @packedFields23 & 0x01
    delayTime             = @buf[@cnt+4] + @buf[@cnt+5]*256
    @transparentColorIndex[@gif] = @buf[@cnt+6]
    blockTerminator       =  @buf[@cnt+7]
    @cnt += 8

    if @debug
      printf "=====================================\n"
      printf "Graphic Control Extension\n"
      printf "=====================================\n"
      printf "Extension Introducer:          0x%02x\n", extensionIntroducer
      printf "Graphic Control Label:         0x%02x\n", graphicControlLabel
      printf "Block Size:                    %d\n", blockSize
      printf "Reserved:                      --\n"
      printf "Disposal Method:               %d\n", disposalMethod
      printf "User Input Flag:               %d\n", userInputFlag
      printf "Transparent Color Flag:        %d\n", @transparentColorFlag[@gif]
      printf "Delay Time:                    %d\n", delayTime
      printf "Transparent Color Index:       %d\n", @transparentColorIndex[@gif]
      printf "Block Terminator:              0x%02x\n", blockTerminator
    end
  end

  ##
  # Comment Extension
  #
  def comment_extension
    extensionIntroducer   = @buf[@cnt]
    commentLabel          = @buf[@cnt+1]
    @cnt += 2
    comment = dataSubBlock()
    
    if @debug
      printf "=====================================\n"
      printf "Comment Extension\n"
      printf "=====================================\n"
      printf "Extension Introducer:          0x%02x\n", extensionIntroducer
      printf "Comment Label:                 0x%02x\n", commentLabel
      printf "Comment Data:                      \n"
      dump(comment)
      printf "Block Terminator:              0x00\n"
    end
  end

  ##
  # Plain Text Extension
  #
  def plaintext_extension
    extensionIntroducer  = @buf[@cnt]
    plainTextLabel       = @buf[@cnt+1]
    blockSize            = @buf[@cnt+2]
    textGridLeftPosition = @buf[@cnt+3] + @buf[@cnt+4]*256
    textGridTopPosition  = @buf[@cnt+5] + @buf[@cnt+6]*256
    textGridWidth        = @buf[@cnt+7] + @buf[@cnt+8]*256
    textGridHeight       = @buf[@cnt+8] + @buf[@cnt+10]*256
    characterCellWidth   = @buf[@cnt+11]
    characterCellHeight  = @buf[@cnt+12]
    textForegroundColorIndex = @buf[@cnt+13]
    textBackgroundColorIndex = @buf[@cnt+14]
    @cnt += 15

    dataSubBlock()

    if @debug
      printf "=====================================\n"
      printf "Plain Text Extension\n"
      printf "=====================================\n"
      printf "Extension Introducer:        0x%02x\n", extensionIntroducer
      printf "Plain Text Label:            0x%02x\n", plainTextLabel
      printf "Block Size:                  0x%02x\n", blockSize
      printf "Text Grid Left Position:     %d\n", textGridLeftPosition
      printf "Text Grid Top Position:      %d\n", textGridTopPosition
      printf "Text Grid Width:             %d\n", textGridWidth
      printf "Text Grid Height:            %d\n", textGridHeight
      printf "Text Foreground Color Index: %d\n", textForegroundColorIndex
      printf "Text Background Color Index: %d\n", textBackgroundColorIndex
      printf "Plain Text Data:             ...\n"
      printf "Block Terminator:            0x00\n"
    end
  end

  ##
  # Application Extension
  #
  def application_extension
    extensionIntroducer           = @buf[@cnt]
    extentionLabel                = @buf[@cnt+1]
    blockSize                     = @buf[@cnt+2]
    applicationIdentifire         = @buf[@cnt+3, 8]
    applicationAuthenticationCode = @buf[@cnt+11, 3]
    @cnt += 14

    dataSubBlock()

    if @debug
      printf "=====================================\n"
      printf "Application Extension\n"
      printf "=====================================\n"
      printf "Extension Introducer:          0x%02x\n",
	extensionIntroducer
      printf "Extension Label:               0x%02x\n",
	plainTextLabel
      printf "Block Size:                    0x%02x\n",
	blockSize
      printf "Application Identifire:        ...\n"
      printf "ApplicationAuthenticationCode: ...\n"
      printf "Block Terminator:              0x00\n"
    end
  end

  ##
  # Trailer
  #
  def trailer
    trailer = @buf[@cnt]
    @cnt += 1

    if @debug
      printf "=====================================\n"
      printf "Trailer\n"
      printf "=====================================\n"
      printf "Trailer:                       0x%02x\n", trailer
      printf "\n"
    end
  end

  ##
  # Data Sub Block
  #
  def dataSubBlock()
    from = @cnt
    while ((n = @buf[@cnt]) != 0 && n != nil)
      @cnt += 1
      @cnt += n
    end
    if !n.nil?
      @cnt += 1
    end
    return @buf[from, @cnt - from]
  end

  ##
  # Memory Dump
  #

  def dump(buf)
    if buf.size == 0
      return
    end
    buf.split(//n).each_with_index{|chr, i|
      if i % 16 == 0
	print "  "
      end
      printf "%02X ", chr[0]
      if i % 16 == 15
	printf "\n"
      end
    }
    if buf.size % 16 != 0
      printf "\n"
    end
  end

end

if __FILE__ == $0
## short cut:
#  print GIFCat.new.read_files("foo.gif", "bar.gif")

## gifファイルの情報出力
#gif =  GIFCat.new
#gif.debug = true
#gif.read_files("tmp1.gif", "tmp2.gif", "tmp3.gif")

### gifファイル連結
gif =  GIFCat.new
gif.read_files("tmp1.gif", "tmp2.gif", "tmp3.gif")
print gif.to_gif

end