varyform

%div.tac
  -# remotipart for ajax image upload
  = form_for Parent.new, url: upload_parent_photo_path, remote: true, html: { id: 'file-form' } do |f|
    #temp-photo.tac{ style: "position: relative; background: url('#{image_path(resource.avatar.url(:thumb))}') center center no-repeat; height: 120px" }
      -# prompt
      = link_to '#', class: 'btn btn-mini btn-light', style: 'opacity: 0.9; position: absolute; bottom: 0; left: 50%; width: 100px; margin-left: -55px' do
        Choose Photo
      -# almost transparent file field which actually receives mouse click and "covers" link above
      = f.file_field :avatar, id: 'temp-avatar', style: 'position: absolute; cursor: pointer; opacity: 0.01; top: 0; left: 0; width: 100%; height: 100%; '