Class: OggAlbumTagger::Picture

Inherits:
Object
  • Object
show all
Defined in:
lib/ogg_album_tagger/picture.rb

Class Method Summary collapse

Class Method Details

.generate_metadata_block_picture(image, desc = '') ⇒ Object

Embed a picture so that it can be included as a tag.

See xiph.org/flac/format.html#metadata_block_picture Note: the type of the picture is currently fixed to “Front cover”, as it is the most common type.

Raises:



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# File 'lib/ogg_album_tagger/picture.rb', line 13

def self.generate_metadata_block_picture(image, desc = '')
  begin
    image = File.expand_path(image)
    img = Exiftool.new(image)
    content = IO.binread(image)
  rescue Exiftool::ExiftoolNotInstalled
    raise OggAlbumTagger::SystemError, "exiftool (the executable, not the gem) is not in your path, please install it."
  rescue
    raise OggAlbumTagger::ArgumentError, "\"#{image}\" cannot be read."
  end

  meta = img.results[0].to_hash
  mime = meta[:mime_type]

  raise OggAlbumTagger::ArgumentError, 'Unsupported image type. Use JPEG or PNG.' unless ['image/png', 'image/jpeg'].include?(mime)

  pack = [
    3, # Front cover
    mime.length,
    mime,
    desc.bytesize,
    desc,
    meta[:image_width],
    meta[:image_height],
    meta[:color_components] * meta[:bits_per_sample],
    0, # palette
    content.length,
    content
  ].pack(sprintf("L>L>A%dL>a%dL>L>L>L>L>a*", mime.length, desc.bytesize))
  Base64.strict_encode64(pack)
end