the error occurs whenever I try to use the class method 'Image.read'

gistfile1.rb

  def img(opt={})
    
    opt[:background_path] ||= "#{Rails.root.to_s}/public/images/citywaypass/card_background.png"
    opt[:background_density] ||= "300x300"
    opt[:font] ||= 'arial'
    opt[:font_weight] ||= 900
    opt[:pointsize] ||= 24
    opt[:width] ||= 2603
    opt[:heigth] ||= 1620
    opt[:text] ||= "Something...."
    
    background = Image.read(opt[:background_path])
    background.first.density = opt[:background_density]

...