html-to-canvas.coffee

pushToServer: ()->
  html2canvas([$(".hidden_container")[0]],{
    onrendered: (canvas)=>
      strDataURI = canvas.toDataURL()
      @temp_container.children().remove()
      @temp_container.hide()

      $.ajax
        url: '/svg/create'
        data: {svg: "#{strDataURI}"}
        dataType: 'json'
        type: 'POST'
        success: (response, status, xhr) =>
          window.location.href = "/downloadable/" + response.id + '.png'
        error: (response, status)=>
          console.log response
  })

svg_server_side.rb

# routes.rb
  match "downloadable/:id(.:format)", :to => 'svg#show'

# svg_controller.rb
class SvgController < ApplicationController
  require "base64"
  
  def show
    @svg = Svg.where(id: params[:id]).first
    respond_to do |format|
      format.png {
        headers['Content-type'] = 'image/png'
        headers["Content-Disposition"] = "attachment; filename=\"chart.png\""
        @result = Base64.decode64(@svg.content.gsub('data:image/png;base64,', ''))
        render :text => @result
      }
    end
  end
end