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