class Asciidoctor::AbstractBlock

def alt

and replacement substitutions applied.
Returns the [String] value of the alt attribute with XML special character

Public: Returns the converted alt text for this block image. 
def alt
  if (text = @attributes['alt'])
    if text == @attributes['default-alt']
      sub_specialchars text
    else
      text = sub_specialchars text
      (ReplaceableTextRx.match? text) ? (sub_replacements text) : text
    end
  else
    ''
  end
end