Class: FilesHunter::Decoders::BMP

Inherits:
BeginPatternDecoder show all
Defined in:
lib/fileshunter/Decoders/BMP.rb

Constant Summary collapse

BEGIN_PATTERN_BMP = 
Regexp.new("BM....\x00\x00\x00\x00", nil, 'n')
PADDING_CHAR = 
"\x00".force_encoding(Encoding::ASCII_8BIT)

Instance Method Summary collapse

Methods inherited from BeginPatternDecoder

#find_segments

Methods inherited from FilesHunter::Decoder

#segments_found, #setup

Instance Method Details

#decode(offset) ⇒ Object 



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# File 'lib/fileshunter/Decoders/BMP.rb', line 15

def decode(offset)
  ending_offset = nil

  cursor = offset + 14
  header_size = BinData::Uint32le.read(@data[cursor..cursor+3])
  width = nil
  height = nil
  bpp = nil
  header_version = nil
  bitmap_size = nil
  compression = 0
  if (header_size == 12)
    # BMP v2 header
    header_version = 2
    width = BinData::Sint16le.read(@data[cursor+4..cursor+5])
    height = BinData::Sint16le.read(@data[cursor+6..cursor+7])
    nbr_planes = BinData::Uint16le.read(@data[cursor+8..cursor+9])
    invalid_data("@#{cursor} - Number of planes (#{nbr_planes}) should always be 1") if (nbr_planes != 1)
    bpp = BinData::Uint16le.read(@data[cursor+10..cursor+11])
    invalid_data("@#{cursor} - Invalid BPP: #{bpp}") if (![1,4,8,16,24,32].include?(bpp))
    cursor += header_size
    # Color palette
    cursor += 3*(1 << bpp) if (bpp != 24)
  else
    # BMP v3+ header
    header_version = 3
    width = BinData::Uint32le.read(@data[cursor+4..cursor+7])
    height = BinData::Uint32le.read(@data[cursor+8..cursor+11])
    nbr_planes = BinData::Uint16le.read(@data[cursor+12..cursor+13])
    invalid_data("@#{cursor} - Number of planes (#{nbr_planes}) should always be 1") if (nbr_planes != 1)
    bpp = BinData::Uint16le.read(@data[cursor+14..cursor+15])
    invalid_data("@#{cursor} - Invalid BPP: #{bpp}") if (![1,4,8,16,24,32].include?(bpp))
    compression = BinData::Uint32le.read(@data[cursor+16..cursor+19])
    invalid_data("@#{cursor} - Invalid compression method: #{compression}") if (compression > 3)
    invalid_data("@#{cursor} - Invalid compression method: #{compression} for given bpp (#{bpp})") if ((compression != 3) and (bpp == 16))
    bitmap_size = BinData::Uint32le.read(@data[cursor+20..cursor+23])
    invalid_data("@#{cursor} - Empty bitmap size for compression method: #{compression}") if ((bitmap_size == 0) and ((compression == 1) or (compression == 2)))
    #ppm_horizontal = BinData::Uint32le.read(@data[cursor+24..cursor+27])
    #ppm_vertical = BinData::Uint32le.read(@data[cursor+28..cursor+31])
    nbr_colors_used = BinData::Uint32le.read(@data[cursor+32..cursor+35])
    invalid_data("@#{cursor} - Number of colors used specified (#{nbr_colors_used} whereas bpp is >= 16 (#{bpp})") if ((bpp >= 16) and (nbr_colors_used > 0))
    #nbr_colors_important = BinData::Uint32le.read(@data[cursor+36..cursor+39])
    if (header_size == 56)
      # BMP v? header
      header_version = 56
    elsif (header_size == 108)
      # BMP v4 header
      header_version = 4
      cstype = BinData::Uint32le.read(@data[cursor+56..cursor+59])
      invalid_data("@#{cursor} - Invalid cstype: #{cstype}") if (cstype > 2)
    end
    cursor += header_size
    # Color palette
    cursor += 4*(1 << bpp) if (bpp < 16)
    cursor += 12 if (((bpp == 16) or (bpp == 32)) and (compression == 3) and (header_version == 3))
  end
  progress(cursor)
  found_relevant_data(:bmp)
  metadata(
    :width => width,
    :height => height,
    :bpp => bpp,
    :header_version => header_version,
    :bitmap_size => bitmap_size,
    :compression => compression
  )
  log_debug "@#{cursor} - Decoding bitmap data: header_version=#{header_version} width=#{width} height=#{height} bpp=#{bpp} compression=#{compression} bitmap_size=#{bitmap_size}"
  if ((compression == 0) or
      (compression == 3))
    # Compute the scanline size
    scanline_size = nil
    case bpp.to_i
    when 1, 4, 8
      scanline_size, extra = width.divmod(8/bpp)
      scanline_size += 1 if (extra > 0)
    when 16, 24, 32
      scanline_size = width * (bpp/8)
      scanline_size *= 2 if ((bpp == 16) and (header_version == 4))
    end
    rest = scanline_size % 4
    scanline_size += 4 - rest if (rest > 0)
    computed_bitmap_size = scanline_size * height
    cursor += computed_bitmap_size
  else
    cursor += bitmap_size
  end
  progress(cursor)
  # Eventually pad to the next 32 bits with \x00
  rest = (cursor - offset) % 4
  if (rest > 0)
    # Check if we have padding
    possible_padding_size = 4 - rest
    cursor += possible_padding_size if ((cursor + possible_padding_size <= @end_offset) and (@data[cursor..cursor + possible_padding_size - 1] == PADDING_CHAR * possible_padding_size))
  end
  ending_offset = cursor

  return ending_offset
end

#get_begin_pattern ⇒ Object 



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# File 'lib/fileshunter/Decoders/BMP.rb', line 11

def get_begin_pattern
  return BEGIN_PATTERN_BMP, { :offset_inc => 2, :max_regexp_size => 10 }
end