Rails images for retina and other high dpi displays using srcset

images_helper.rb

module ImagesHelper
  # Outputs html img tag with srcset attribute for 2x image based on original
  # src. Use naming convention ex. having 'image.jpg', 2x image should be named
  # 'image@2x.jpg'. If there's no image.jpg or image@2x.jpg exception will be
  # thrown by Rails asset pipeline.
  def retina_image(src, options = {})
    src2x = src.gsub(/(^.+)(\.(jpg|png)$)/, '\1@2x\2')    
    image_tag src, options.merge(srcset: "#{image_url(src2x)} 2x")
  end
end