Class: ImageRuby::BmpDecoder

Inherits:
Decoder
  • Object
show all
Defined in:
lib/imageruby-bmp.rb

Instance Method Summary collapse

Instance Method Details

#decode(data, image_class) ⇒ Object 



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# File 'lib/imageruby-bmp.rb', line 25

def decode(data, image_class)

  # read bmp header
  header = data[0..13]
  dib_header = data[14..54]

  magic = header[0..1]

  # check magic
  unless magic == "BM"
    raise UnableToDecodeException
  end

  pixeldata_offset = header[10..13].unpack("L").first

  width = dib_header[4..7].unpack("L").first
  height = dib_header[8..11].unpack("L").first

  # create image object

  image = image_class.new(width,height)

  padding_size = ( 4 - (width * 3 % 4) ) % 4
  width_array_len = width*3 + padding_size

  # read pixel data
  height.times do |y|
    offset = pixeldata_offset+(height-y-1)*width_array_len
    index = (y*width)*3
    image.pixel_data[index..index+width*3] = data[offset..offset+width*3]
  end

  image

end