Responsive Images with Scrivito

show.html.erb

<%= scrivito_image_tag widget, :image, {
  class: 'image-widget',
  srcset: srcset_for(widget.image)
}, transform: {width: 1280} %>

srcset_helper.rb

module SrcsetHelper
  
  # polyfill for browsers that do not support srcset:
  # https://scottjehl.github.io/picturefill/
  def srcset_for(obj)
    image = obj.try(:binary)
    return unless image

    [160, 320, 640, 1280, 2560].map do |width|
      transformed_image = image.transform(width: width)
      url = scrivito_url(transformed_image)

      "#{url} #{width}w"
    end.join(", ")
  end
end