Implement <image> support for SVG documents

This allows <image> elements to reference SVG documents so they can be
embedded inside the top-level SVG document.

Implements #137 and #144

README.md

@@ -70,8 +70,9 @@ prawn-svg supports most but not all of the full SVG 1.1 specification.  It curre
 
  - <tt>&lt;style&gt;</tt> (see CSS section below)
 
- - `<image>` referencing a JPEG or PNG image,  with `http:`, `https:`, `data:image/jpeg;base64`, `data:image/png;base64` and `file:` schemes
-   (`file:` is disabled by default for security reasons, see Options section above)
+ - `<image>` referencing a JPEG, PNG, or SVG image,  with `http:`, `https:`, `data:image/jpeg;base64`,
+   `data:image/png;base64`, `data:image/svg+xml;base64` and `file:` schemes (`file:` is disabled by default for
+   security reasons, see Options section above)
 
  - <tt>&lt;clipPath&gt;</tt>
 

lib/prawn-svg.rb

@@ -21,6 +21,7 @@
 require 'prawn/svg/pathable'
 require 'prawn/svg/elements'
 require 'prawn/svg/extension'
+require 'prawn/svg/renderer'
 require 'prawn/svg/interface'
 require 'prawn/svg/css/font_family_parser'
 require 'prawn/svg/css/selector_parser'

lib/prawn/svg/document.rb

@@ -16,7 +16,7 @@ class Prawn::SVG::Document
     :element_styles,
     :color_mode
 
-  def initialize(data, bounds, options, font_registry: nil, css_parser: CssParser::Parser.new)
+  def initialize(data, bounds, options, font_registry: nil, css_parser: CssParser::Parser.new, attribute_overrides: {})
     @root = REXML::Document.new(data).root
 
     if @root.nil?
@@ -41,7 +41,10 @@ def initialize(data, bounds, options, font_registry: nil, css_parser: CssParser:
       enable_file_with_root: options[:enable_file_requests_with_root]
     )
 
-    @sizing = Prawn::SVG::Calculators::DocumentSizing.new(bounds, @root.attributes)
+    attributes = @root.attributes.dup
+    attribute_overrides.each { |key, value| attributes.add(REXML::Attribute.new(key, value)) }
+
+    @sizing = Prawn::SVG::Calculators::DocumentSizing.new(bounds, attributes)
     calculate_sizing(requested_width: options[:width], requested_height: options[:height])
 
     @element_styles = Prawn::SVG::CSS::Stylesheets.new(css_parser, root).load

lib/prawn/svg/elements/image.rb

@@ -3,29 +3,32 @@ class FakeIO
     def initialize(data)
       @data = data
     end
+
     def read
       @data
     end
-    def rewind
-    end
+
+    def rewind; end
   end
 
+  ImageData = Struct.new(:dimensions, :document)
+
   def parse
     require_attributes 'width', 'height'
 
-    raise SkipElementQuietly if state.computed_properties.display == "none"
+    raise SkipElementQuietly if state.computed_properties.display == 'none'
 
     @url = href_attribute
-    if @url.nil?
-      raise SkipElementError, "image tag must have an href or xlink:href"
-    end
+    raise SkipElementError, 'image tag must have an href or xlink:href' if @url.nil?
 
     x = x(attributes['x'] || 0)
     y = y(attributes['y'] || 0)
     width = x_pixels(attributes['width'])
     height = y_pixels(attributes['height'])
+    preserveAspectRatio = attributes['preserveAspectRatio']
 
     raise SkipElementQuietly if width.zero? || height.zero?
+
     require_positive_value width, height
 
     @image = begin
@@ -34,7 +37,9 @@ def parse
       raise SkipElementError, "Error retrieving URL #{@url}: #{e.message}"
     end
 
-    @aspect = Prawn::SVG::Calculators::AspectRatio.new(attributes['preserveAspectRatio'], [width, height], image_dimensions(@image))
+    @image_data = process_image(@image, width, height, preserveAspectRatio)
+
+    @aspect = Prawn::SVG::Calculators::AspectRatio.new(preserveAspectRatio, [width, height], @image_data.dimensions)
 
     @clip_x = x
     @clip_y = y
@@ -49,15 +54,21 @@ def parse
 
   def apply
     if @aspect.slice?
-      add_call "save"
-      add_call "rectangle", [@clip_x, @clip_y], @clip_width, @clip_height
-      add_call "clip"
+      add_call 'save'
+      add_call 'rectangle', [@clip_x, @clip_y], @clip_width, @clip_height
+      add_call 'clip'
     end
 
-    options = {:width => @width, :height => @height, :at => [@x, @y]}
+    if (document = @image_data.document)
+      add_call_and_enter 'translate', @x, @y
+      add_call 'svg:render_sub_document', document
+    else
+      options = { width: @width, height: @height, at: [@x, @y] }
+
+      add_call 'image', FakeIO.new(@image), options
+    end
 
-    add_call "image", FakeIO.new(@image), options
-    add_call "restore" if @aspect.slice?
+    add_call 'restore' if @aspect.slice?
   end
 
   def bounding_box
@@ -66,15 +77,38 @@ def bounding_box
 
   protected
 
-  def image_dimensions(data)
-    unless (handler = find_image_handler(data))
-      raise SkipElementError, 'Unsupported image type supplied to image tag'
+  def process_image(data, width, height, preserveAspectRatio)
+    if (handler = find_image_handler(data))
+      image = handler.new(data)
+      ImageData.new([image.width.to_f, image.height.to_f], nil)
+
+    elsif potentially_svg?(data)
+      document = Prawn::SVG::Document.new(
+        data, [width, height], { width: width, height: height },
+        attribute_overrides: { 'preserveAspectRatio' => preserveAspectRatio }
+      )
+
+      dimensions = [document.sizing.output_width, document.sizing.output_height]
+      ImageData.new(dimensions, document)
+
+    else
+      raise_invalid_image_type
     end
-    image = handler.new(data)
-    [image.width.to_f, image.height.to_f]
+  rescue Prawn::SVG::Document::InvalidSVGData
+    raise_invalid_image_type
   end
 
   def find_image_handler(data)
-    Prawn.image_handler.find(data) rescue nil
+    Prawn.image_handler.find(data)
+  rescue StandardError
+    nil
+  end
+
+  def potentially_svg?(data)
+    data.include?('<svg')
+  end
+
+  def raise_invalid_image_type
+    raise SkipElementError, 'Unsupported image type supplied to image tag'
   end
 end