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Finding the Bounding Box of an SVG Path in Ruby

Here is a way for finding out the bounding box (left, right, width and height) of an SVG path in Ruby. You will need ImageMagick and RMagick for this. In Javascript this is quite simple using the getBBox method, but I couldn’t find a similar thing in Ruby.

First install ImageMagick if you don’t have it already. I like to use Homebrew:

brew install imagemagick

Then install RMagick

gem install rmagick

With these two requirements in place you can find the bounding box using a script like this:

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 require 'rubygems'
  require 'RMagick'
  
  def find_bounding_box(path)
      include Magick  
  
      #create a drawing object
      drawing = Magick::Draw.new
  
  
      #create a new image for finding out the offset
      canvas = Image.new(1500,1000) {self.background_color = 'white' }
  
      #draw the path into the canvas image
      drawing.path path
      drawing.draw canvas
  
      #trim the whitespace of the image
      canvas.trim!   
  
      #here is the bounding box information we are looking for
      { :x=> canvas.page.x, :y=>canvas.page.y, :width=> canvas.columns, :height=> canvas.rows}
  end

Let’s test it:

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 svg_path = "M555.545,95.489c-9.67,4.589-19.34,9.178-29.01,13.767c9.097,19.235,18.194,38.47,27.291,57.705c9.667-4.598,19.335-9.196,29.002-13.794C573.733,133.941,564.64,114.715,555.545,95.489z"
  
  bbox = find_bounding_box(svg_path)
  
  puts "x="+bbox[:x].to_s
  puts "y="+bbox[:y].to_s
  puts "width="+bbox[:width].to_s
  puts "height="+bbox[:height].to_s

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