Module: Asciidoctor::Diagram::PNG

Defined in:
lib/asciidoctor-diagram/util/png.rb

Constant Summary collapse

PNG_SIGNATURE = 
[137, 80, 78, 71, 13, 10, 26, 10].pack('CCCCCCCC')

Class Method Summary collapse

Class Method Details

.post_process_image(data, optimise) ⇒ Object 



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# File 'lib/asciidoctor-diagram/util/png.rb', line 9

def self.post_process_image(data, optimise)
  bio = BinaryIO.new(data)
  png_signature = bio.read_string(8)
  raise "Invalid PNG signature" unless png_signature == PNG_SIGNATURE

  chunk_length = bio.read_uint32_be
  chunk_type = bio.read_string(4, Encoding::US_ASCII)
  raise "Unexpected PNG chunk type '#{chunk_type}'; expected 'IHDR'" unless chunk_type == 'IHDR'
  raise "Unexpected PNG chunk length '#{chunk_length}'; expected '13'" unless chunk_length == 13

  width = bio.read_uint32_be
  height = bio.read_uint32_be
  [data, width, height]
end