SVG Generator spike with same RVG API from RMagick. (output svg xml only)

svg.rb

require 'rexml/document'

class SVG

  def initialize(width, height)
		@doc = REXML::Document.new
		@doc << REXML::XMLDecl.new
		@svg = @doc.add_element 'svg'
		@svg.add_attribute 'xmlns', 'http://www.w3.org/2000/svg'
		@svg.add_attribute 'width', width
		@svg.add_attribute 'height', height
		@canvas = Node.new @svg.add_element 'g'

		yield @canvas
	end

	def to_xml
		@doc.to_s
	end

	class Node
		def self.node_attribute(*attrs)
			attrs.each do |attr|
				self.class_eval %Q{
					def #{attr}=(val)
						xml_node.add_attribute '#{attr}', val
					end
				}
			end
		end

		def self.style_attribute(*attrs)
			attrs.each do |attr|
				self.class_eval %Q{
					def #{attr}=(val)
						@styles[:#{attr}] = val
						write_style
					end
				}
			end
		end

		attr_reader :xml_node

		node_attribute :x, :y, :width, :height, :d
		style_attribute :background_fill_opacity, :background_fill

		def initialize(xml_node)
			@xml_node = xml_node
			@styles = {}
			@transform = ''
		end

		def styles(options)
			@styles.merge! options
			write_style
		end

		def translate(x, y)
			@transform << "translate(#{x} #{y}) "
			write_transform
			yield self if block_given?
			self
		end

		def scale(s)
			@transform << "scale(#{s}) "
			write_transform
			yield self if block_given?
			self
		end

		def g
			res = Node.new xml_node.add_element 'g'
			yield res if block_given?
			res
		end

		def path(path)
			res = Node.new xml_node.add_element 'path'
			res.d = path
			res
		end

		def text(x, y)
			res = Node.new xml_node.add_element 'text'
			res.x = x
			res.y = y
			yield res if block_given?
			res
		end

		def tspan(text)
			res = Node.new xml_node.add_element 'tspan'
			res.xml_node.text = text
			res
		end

		def rect(width, height, x, y)
			res = Node.new xml_node.add_element 'rect'
			res.x = x
			res.y = y
			res.width = width
			res.height = height
			res
		end

		private

		def write_transform
			@xml_node.add_attribute 'transform', @transform unless @transform.empty?
		end

		def write_style
			style = (@styles.map { |key, value| "#{to_svg_style_name(key)}:#{value}" }).join(';')
			@xml_node.add_attribute 'style', style unless style.empty?
		end

		def to_svg_style_name(options_name)
			options_name.to_s.gsub '_', '-'
		end
	end
end