class ImageSize

# File lib/image_size.rb, line 51
def self.dpi
  @dpi || 72
end

# File lib/image_size.rb, line 56
def self.dpi=(dpi)
  @dpi = dpi.to_f
end

# File lib/image_size.rb, line 61
def initialize(data)
  ir = ImageReader.new(data)
  @format = detect_format(ir)
  return unless @format

  @width, @height = send("size_of_#{@format}", ir)
end

# File lib/image_size.rb, line 46
def self.path(path)
  File.open(path, 'rb'){ |f| new(f) }
end

# File lib/image_size.rb, line 81
def size
  Size.new([width, height]) if format
end

# File lib/image_size.rb, line 89
def detect_format(ir)
  head = ir[0, 1024]
  case
  when head[0, 6] =~ /GIF8[79]a/                                then :gif
  when head[0, 8] == "\211PNG\r\n\032\n"                        then detect_png_type(ir)
  when head[0, 8] == "\212MNG\r\n\032\n"                        then :mng
  when head[0, 2] == "\377\330"                                 then :jpeg
  when head[0, 2] == 'BM'                                       then :bmp
  when head[0, 3] =~ /P[1-6]\s|P7\n/                            then detect_pnm_type(ir)
  when head =~ /\#define\s+\S+\s+\d+/                           then :xbm
  when %W[II*\0 MM\0*].include?(head[0, 4])                     then :tiff
  when head =~ %r{/\* XPM \*/}                                  then :xpm
  when head[0, 4] == '8BPS'                                     then :psd
  when head[0, 3] =~ /[FC]WS/                                   then :swf
  when head =~ SVG_R || (head =~ XML_R && ir[0, 4096][SVG_R])   then :svg
  when head[0, 2] =~ /\n[\0-\5]/                                then :pcx
  when head[0, 12] =~ /RIFF(?m:....)WEBP/                       then :webp
  when head[0, 4] == "\0\0\1\0"                                 then :ico
  when head[0, 4] == "\0\0\2\0"                                 then :cur
  when head[0, 12] == "\0\0\0\fjP  \r\n\207\n"                  then detect_jpeg2000_type(ir)
  when head[0, 4] == "\377O\377Q"                               then :j2c
  end
end

# File lib/image_size.rb, line 135
def detect_jpeg2000_type(ir)
  return unless ir[16, 4] == 'ftyp'

  # using xl-box would be weird, but doesn't seem to contradict specification
  skip = ir[12, 4] == "\0\0\0\1" ? 16 : 8
  case ir[12 + skip, 4]
  when 'jp2 ' then :jp2
  when 'jpx ' then :jpx
  end
end

# File lib/image_size.rb, line 113
def detect_png_type(ir)
  offset = 8
  loop do
    type = ir[offset + 4, 4]
    break if ['IDAT', 'IEND', nil].include?(type)
    return :apng if type == 'acTL'

    length = ir[offset, 4].unpack('N')[0]
    offset += 8 + length + 4
  end
  :png
end

# File lib/image_size.rb, line 126
def detect_pnm_type(ir)
  case ir[0, 2]
  when 'P1', 'P4' then :pbm
  when 'P2', 'P5' then :pgm
  when 'P3', 'P6' then :ppm
  when 'P7'       then :pam
  end
end

# File lib/image_size.rb, line 192
def size_of_bmp(ir)
  header_size = ir[14, 4].unpack('V')[0]
  if header_size == 12
    ir[18, 4].unpack('vv')
  else
    ir[18, 8].unpack('VV').map do |n|
      if n > 0x7fff_ffff
        0x1_0000_0000 - n # absolute value of converted to signed
      else
        n
      end
    end
  end
end

# File lib/image_size.rb, line 146
def size_of_gif(ir)
  ir[6, 4].unpack('vv')
end

# File lib/image_size.rb, line 332
def size_of_ico(ir)
  ir[6, 2].unpack('CC').map{ |v| v.zero? ? 256 : v }
end

# File lib/image_size.rb, line 386
def size_of_j2c(ir)
  ir[8, 8].unpack('NN')
end

# File lib/image_size.rb, line 350
def size_of_jp2(ir)
  offset = 12
  stop = nil
  in_header = false
  loop do
    break if stop && offset >= stop
    break if ir[offset, 4] == '' || ir[offset, 4].nil?

    size = ir[offset, 4].unpack('N')[0]
    type = ir[offset + 4, 4]

    data_offset = 8
    case size
    when 1
      size = ir[offset, 8].unpack('Q>')[0]
      data_offset = 16
      raise FormatError, "Unexpected xl-box size #{size}" if (1..15).include?(size)
    when 2..7
      raise FormatError, "Reserved box size #{size}"
    end

    if type == 'jp2h'
      stop = offset + size unless size.zero?
      offset += data_offset
      in_header = true
    elsif in_header && type == 'ihdr'
      return ir[offset + data_offset, 8].unpack('NN').reverse
    else
      break if size.zero? # box to the end of file

      offset += size
    end
  end
end

# File lib/image_size.rb, line 173
def size_of_jpeg(ir)
  section_marker = "\xFF"
  offset = 2
  loop do
    offset += 1 until [nil, section_marker].include? ir[offset, 1]
    offset += 1 until section_marker != ir[offset + 1, 1]
    raise FormatError, 'EOF in JPEG' if ir[offset, 1].nil?

    _marker, code, length = ir[offset, 4].unpack('aCn')
    offset += 4

    if JPEG_CODE_CHECK.include?(code)
      return ir[offset + 1, 4].unpack('nn').reverse
    end

    offset += length - 2
  end
end

# File lib/image_size.rb, line 150
def size_of_mng(ir)
  unless ir[12, 4] == 'MHDR'
    raise FormatError, 'MHDR not in place for MNG'
  end

  ir[16, 8].unpack('NN')
end

# File lib/image_size.rb, line 216
def size_of_pam(ir)
  width = height = nil
  offset = 3
  loop do
    if ir[offset, 1] == '#'
      offset += 1 until ["\n", '', nil].include?(ir[offset, 1])
      offset += 1
    else
      chunk = ir[offset, 32]
      case chunk
      when /\AWIDTH (\d+)\n/
        width = $1.to_i
      when /\AHEIGHT (\d+)\n/
        height = $1.to_i
      when /\AENDHDR\n/
        break
      when /\A(?:DEPTH|MAXVAL) \d+\n/, /\ATUPLTYPE \S+\n/
        # ignore
      else
        raise FormatError, "Unexpected data in PAM header: #{chunk.inspect}"
      end
      offset += $&.length
      break if width && height
    end
  end
  [width, height]
end

# File lib/image_size.rb, line 296
def size_of_pcx(ir)
  parts = ir[4, 8].unpack('v4')
  [parts[2] - parts[0] + 1, parts[3] - parts[1] + 1]
end

# File lib/image_size.rb, line 158
def size_of_png(ir)
  unless ir[12, 4] == 'IHDR'
    raise FormatError, 'IHDR not in place for PNG'
  end

  ir[16, 8].unpack('NN')
end

# File lib/image_size.rb, line 207
def size_of_ppm(ir)
  header = ir[0, 1024]
  header.gsub!(/^\#[^\n\r]*/m, '')
  header =~ /^(P[1-6])\s+?(\d+)\s+?(\d+)/m
  [$2.to_i, $3.to_i]
end

# File lib/image_size.rb, line 261
def size_of_psd(ir)
  ir[14, 8].unpack('NN').reverse
end

# File lib/image_size.rb, line 310
def size_of_svg(ir)
  attributes = {}
  ir.data[SVG_R, 1].scan(/(\S+)=(?:'([^']*)'|"([^"]*)"|([^'"\s]*))/) do |name, v0, v1, v2|
    attributes[name] = v0 || v1 || v2
  end
  dpi = self.class.dpi
  [attributes['width'], attributes['height']].map do |length|
    next unless length

    pixels = case length.downcase.strip[/(?:em|ex|px|in|cm|mm|pt|pc|%)\z/]
    when 'em', 'ex', '%' then nil
    when 'in' then length.to_f * dpi
    when 'cm' then length.to_f * dpi / 2.54
    when 'mm' then length.to_f * dpi / 25.4
    when 'pt' then length.to_f * dpi / 72
    when 'pc' then length.to_f * dpi / 6
    else length.to_f
    end
    pixels.round if pixels
  end
end

# File lib/image_size.rb, line 301
def size_of_swf(ir)
  value_bit_length = ir[8, 1].unpack('B5').first.to_i(2)
  bit_length = 5 + value_bit_length * 4
  rect_bits = ir[8, bit_length / 8 + 1].unpack("B#{bit_length}").first
  values = rect_bits[5..-1].unpack("a#{value_bit_length}" * 4).map{ |bits| bits.to_i(2) }
  x_min, x_max, y_min, y_max = values
  [(x_max - x_min) / 20, (y_max - y_min) / 20]
end

# File lib/image_size.rb, line 265
def size_of_tiff(ir)
  endian2b = ir[0, 4] == "II*\000" ? 'v' : 'n'
  endian4b = endian2b.upcase
  packspec = [nil, 'C', nil, endian2b, endian4b, nil, 'c', nil, endian2b, endian4b]

  offset = ir[4, 4].unpack(endian4b)[0]
  num_dirent = ir[offset, 2].unpack(endian2b)[0]
  offset += 2
  num_dirent = offset + (num_dirent * 12)

  width = height = nil
  until width && height
    ifd = ir[offset, 12]
    raise FormatError, 'Reached end of directory entries in TIFF' if ifd.nil? || offset > num_dirent

    tag, type = ifd.unpack(endian2b * 2)
    offset += 12

    next if packspec[type].nil?

    value = ifd[8, 4].unpack(packspec[type])[0]
    case tag
    when 0x0100
      width = value
    when 0x0101
      height = value
    end
  end
  [width, height]
end

# File lib/image_size.rb, line 337
def size_of_webp(ir)
  case ir[12, 4]
  when 'VP8 '
    ir[26, 4].unpack('vv').map{ |v| v & 0x3fff }
  when 'VP8L'
    n = ir[21, 4].unpack('V')[0]
    [(n & 0x3fff) + 1, (n >> 14 & 0x3fff) + 1]
  when 'VP8X'
    w16, w8, h16, h8 = ir[24, 6].unpack('vCvC')
    [(w16 | w8 << 16) + 1, (h16 | h8 << 16) + 1]
  end
end

# File lib/image_size.rb, line 244
def size_of_xbm(ir)
  ir[0, 1024] =~ /^\#define\s*\S*\s*(\d+)\s*\n\#define\s*\S*\s*(\d+)/mi
  [$1.to_i, $2.to_i]
end

# File lib/image_size.rb, line 249
def size_of_xpm(ir)
  length = 1024
  until (data = ir[0, length]) =~ /"\s*(\d+)\s+(\d+)(\s+\d+\s+\d+){1,2}\s*"/m
    if data.length != length
      raise FormatError, 'XPM size not found'
    end

    length += 1024
  end
  [$1.to_i, $2.to_i]
end