# File lib/png/reader.rb, line 34 def self.read_chunk expected_type, png size, type = png.slice!(0, 8).unpack 'Na4' data, crc = png.slice!(0, size + 4).unpack "a#{size}N" check_crc type, data, crc raise ArgumentError, "Expected #{expected_type} chunk, not #{type}" unless type == expected_type return data end