Modifying an image URL based on hash options

The code I'm trying to improve modifies a URL according to the options passed in a hash:

{
  :image_aspect_ratio => "square",
  :image_size => 50
}

or

{
  :image_size => {
    :width => 50,
    :height => 60
  }
}

The code looks like this:

module X
  module Y
    class Z


def image_url
  if raw_info['picture'] && image_size_opts_passed?
    image_url_with_size_opts
  else
    raw_info['picture']
  end
end

def image_size_opts_passed?
  !!(options[:image_size] || options[:image_aspect_ratio])
end

def image_url_with_size_opts
  params_index = raw_info['picture'].index('/photo.jpg')
  if params_index
    raw_info['picture'].insert(params_index, image_params)
  else
    raw_info['picture']
  end
end

def image_params
  image_params = []
  if options[:image_size].is_a?(Integer)
    image_params << "s#{options[:image_size]}"
  elsif options[:image_size].is_a?(Hash)
    image_params << "w#{options[:image_size][:width]}" if options[:image_size][:width]
    image_params << "h#{options[:image_size][:height]}" if options[:image_size][:height]
  end
  image_params << 'c' if options[:image_aspect_ratio] == 'square'

  '/' + image_params.join('-')
end

Here's the stuff I hate about this code:

1. Lots of raw_info['picture'] being called, but I'm not sure if using a local variable is better than accessing a hash twice.

2. I'm seeing some duplication in the else branch in the image_url and image_url_with_size_opts methods but I don't know how to improve that.

3. This code is all inside a class which is inside a module which is inside another module, so I'm not sure if I could also memoize the image_params result.