Class: FastImageParsing::TypeParser

Inherits:
Object
  • Object
show all
Defined in:
lib/fastimage/fastimage_parsing/type_parser.rb

Instance Method Summary collapse

Constructor Details

#initialize(stream) ⇒ TypeParser

Returns a new instance of TypeParser.



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# File 'lib/fastimage/fastimage_parsing/type_parser.rb', line 3

def initialize(stream)
  @stream = stream
end

Instance Method Details

#type ⇒ Object

type will use peek to get enough bytes to determing the type of the image



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# File 'lib/fastimage/fastimage_parsing/type_parser.rb', line 8

def type
  parsed_type = case @stream.peek(2)
  when "BM"
    :bmp
  when "GI"
    :gif
  when 0xff.chr + 0xd8.chr
    :jpeg
  when 0x89.chr + "P"
    :png
  when "II", "MM"
    case @stream.peek(11)[8..10]
    when "APC", "CR\002"
      nil  # do not recognise CRW or CR2 as tiff
    else
      :tiff
    end
  when '8B'
    :psd
  when "\xFF\x0A".b
    :jxl
  when "\0\0"
    case @stream.peek(3).bytes.to_a.last
    when 0
      # http://www.ftyps.com/what.html
      case @stream.peek(12)[4..-1]
      when "ftypavif"
        :avif
      when "ftypavis"
        :avif
      when "ftypheic"
        :heic
      when "ftypmif1"
        :heif
      else
        if @stream.peek(7)[4..-1] == 'JXL'
          :jxl
        end
      end
    # ico has either a 1 (for ico format) or 2 (for cursor) at offset 3
    when 1 then :ico
    when 2 then :cur
    end
  when "RI"
    :webp if @stream.peek(12)[8..11] == "WEBP"
  when "<s"
    :svg if @stream.peek(4) == "<svg"
  when /\s\s|\s<|<[?!]/, 0xef.chr + 0xbb.chr
    # Peek 10 more chars each time, and if end of file is reached just raise
    # unknown. We assume the <svg tag cannot be within 10 chars of the end of
    # the file, and is within the first 1000 chars.
    begin
      :svg if (1..100).detect {|n| @stream.peek(10 * n).include?("<svg")}
    rescue FiberError, FastImage::CannotParseImage
      nil
    end
  end

  parsed_type or raise FastImage::UnknownImageType
end