gistfile1.rb

class SvgController < ApplicationController
  require 'active_support/secure_random'    
  
  def create
    # create an SVG image
    # based on Highcharts index.php
    batik_path = Rails.root.to_s() + '/vendor/batik/batik-rasterizer.jar'
    
    svg = params[:svg]
    filename = params[:filename].blank? ? "chart" : params[:filename]
    
    if params[:type] == 'image/png' 
      type = '-m image/png';
      ext = 'png'
    elsif params[:type] == 'image/jpeg' 
      type = '-m image/jpeg'
      ext = 'jpg'
    elsif params[:type]  == 'application/pdf'
      type = '-m application/pdf'
      ext = 'pdf'
    else
      show_error "unknown image type: #{params[:type]}"
    end
  
    # two random file names - one for Batik to read (with SVG XML) and one for it to write to
    tempname = ActiveSupport::SecureRandom.hex(16)
    outfile = "tmp/#{tempname}.#{ext}"
    infile = "tmp/#{tempname}.svg"
    width = "-w #{params[:width]}" if params[:width]    

     # do the conversion
    File.open(infile, 'w') {|f| f.write(svg) }          # SVG definition for Batik to read     
    cmd = "java -jar #{batik_path} #{type} -d #{outfile} #{width} #{infile}"
    logger.info(cmd)
    rsp = system(cmd)
      
     # For now, rely on existence and size of output file as an idicator of success
     fs = File.size?( outfile)
     if fs.nil? || fs < 10
       show_error( "Output file empty;  #{rsp}")   
    else       
       # Send output back to user; note use of :stream => false so that we can delete the file (otherwise we don't know when stream is complete...)
        send_file outfile, :type => params[:type], :filename=> "#{filename}.#{ext}", :disposition => 'attachment', :stream => false
     end
     
     File.delete( infile, outfile)
  end
  
  def show_error(rsp)
    render :text => "Unable to export image; #{rsp}", :status => 500
  end
end