Ruby, RSVG and PNG streams

Question

I\'m trying to do an image conversion in a rails app from SVG to PNG. ImageMagick didn\'t work out for me, due to Heroku not able / wanting to upgrade IM at this time. I\'m te

Answer 1

Ah ha! I was so close and its pretty obvious in hindsight. Simply call the surface.write_to_png function with a StringIO object. This fills the string object, which you can then get the bytes for. Here's the finished svg_to_png function I wrote, along with a sample controller that calls it. Hope this helps someone else somewhere.

ImageConvert function:

  def self.svg_to_png(svg)
    svg = RSVG::Handle.new_from_data(svg)
    surface = Cairo::ImageSurface.new(Cairo::FORMAT_ARGB32, 800, 800)
    context = Cairo::Context.new(surface)
    context.render_rsvg_handle(svg)
    b = StringIO.new
    surface.write_to_png(b)
    return b.string
  end

Test controller:

  def svg_img
    path = File.expand_path('../../../public/images/test.svg', __FILE__)
    f = File.open(path, 'r')
    t = ImageConvert.svg_to_png(f.read)
    send_data(t , :filename => 'test.png', :type=>'image/png')
  end