Implement gradientTransform on <linearGradient>

Also implements the missing skewX and skewY transforms to normal
transforms.

Requested on #112

README.md

@@ -76,7 +76,7 @@ prawn-svg supports most but not all of the full SVG 1.1 specification.  It curre
 
  - `<marker>`
 
- - `<linearGradient>` is implemented with Prawn 2.2.0+ (gradientTransform, spreadMethod and stop-opacity are unimplemented.)
+ - `<linearGradient>` is implemented on Prawn 2.2.0+ with attributes `gradientUnits` and `gradientTransform` (spreadMethod and stop-opacity are unimplemented.)
 
  - `<switch>` and `<foreignObject>`, although prawn-svg cannot handle any data that is not SVG so `<foreignObject>`
    tags are always ignored.
@@ -91,7 +91,7 @@ prawn-svg supports most but not all of the full SVG 1.1 specification.  It curre
 
  - the <tt>preserveAspectRatio</tt> attribute on <tt>&lt;svg&gt;</tt>, <tt>&lt;image&gt;</tt> and `<marker>` elements
 
- - transform methods: <tt>translate()</tt>, <tt>rotate()</tt>, <tt>scale()</tt>, <tt>matrix()</tt>
+ - transform methods: `translate`, `translateX`, `translateY`, `rotate`, `scale`, `skewX`, `skewY`, `matrix`
 
  - colors: HTML standard names, <tt>#xxx</tt>, <tt>#xxxxxx</tt>, <tt>rgb(1, 2, 3)</tt>, <tt>rgb(1%, 2%, 3%)</tt>
 

lib/prawn-svg.rb

@@ -10,6 +10,7 @@
 require 'prawn/svg/calculators/aspect_ratio'
 require 'prawn/svg/calculators/document_sizing'
 require 'prawn/svg/calculators/pixels'
+require 'prawn/svg/transform_parser'
 require 'prawn/svg/url_loader'
 require 'prawn/svg/loaders/data'
 require 'prawn/svg/loaders/file'
@@ -29,6 +30,9 @@
 require 'prawn/svg/document'
 require 'prawn/svg/state'
 
+require 'prawn/svg/extensions/additional_gradient_transforms'
+Prawn::Document.prepend Prawn::SVG::Extensions::AdditionalGradientTransforms
+
 module Prawn
   Svg = SVG # backwards compatibility
 end

lib/prawn/svg/attributes/transform.rb

@@ -2,49 +2,7 @@ module Prawn::SVG::Attributes::Transform
   def parse_transform_attribute_and_call
     return unless transform = attributes['transform']
 
-    parse_css_method_calls(transform).each do |name, arguments|
-      case name
-      when 'translate'
-        x, y = arguments
-        add_call_and_enter name, x_pixels(x.to_f), -y_pixels(y.to_f)
-
-      when 'rotate'
-        r, x, y = arguments.collect {|a| a.to_f}
-        case arguments.length
-        when 1
-          add_call_and_enter name, -r, :origin => [0, y('0')]
-        when 3
-          add_call_and_enter name, -r, :origin => [x(x), y(y)]
-        else
-          warnings << "transform 'rotate' must have either one or three arguments"
-        end
-
-      when 'scale'
-        x_scale = arguments[0].to_f
-        y_scale = (arguments[1] || x_scale).to_f
-        add_call_and_enter "transformation_matrix", x_scale, 0, 0, y_scale, 0, 0
-
-      when 'matrix'
-        if arguments.length != 6
-          warnings << "transform 'matrix' must have six arguments"
-        else
-          a, b, c, d, e, f = arguments.collect {|argument| argument.to_f}
-          add_call_and_enter "transformation_matrix", a, -b, -c, d, x_pixels(e), -y_pixels(f)
-        end
-
-      else
-        warnings << "Unknown transformation '#{name}'; ignoring"
-      end
-    end
-  end
-
-  private
-
-  def parse_css_method_calls(string)
-    string.scan(/\s*(\w+)\(([^)]+)\)\s*/).collect do |call|
-      name, argument_string = call
-      arguments = argument_string.strip.split(/\s*[,\s]\s*/)
-      [name, arguments]
-    end
+    matrix = parse_transform_attribute(transform)
+    add_call_and_enter "transformation_matrix", *matrix unless matrix == [1, 0, 0, 1, 0, 0]
   end
 end

lib/prawn/svg/elements/base.rb

@@ -11,6 +11,8 @@ class Prawn::SVG::Elements::Base
   include Prawn::SVG::Attributes::Stroke
   include Prawn::SVG::Attributes::Space
 
+  include Prawn::SVG::TransformParser
+
   PAINT_TYPES = %w(fill stroke)
   COMMA_WSP_REGEXP = Prawn::SVG::Elements::COMMA_WSP_REGEXP
   SVG_NAMESPACE = "http://www.w3.org/2000/svg"

lib/prawn/svg/elements/gradient.rb

@@ -32,7 +32,11 @@ def gradient_arguments(element)
       to   = [@x2, @y2]
     end
 
-    {from: from, to: to, stops: @stops}
+    # Passing in a transformation matrix to the apply_transformations option is supported
+    # by a monkey patch installed by prawn-svg.  Prawn only sees this as a truthy variable.
+    #
+    # See Prawn::SVG::Extensions::AdditionalGradientTransforms for details.
+    {from: from, to: to, stops: @stops, apply_transformations: @transform_matrix || true}
   end
 
   private
@@ -51,10 +55,7 @@ def load_gradient_configuration
     @units = attributes["gradientUnits"] == 'userSpaceOnUse' ? :user_space : :bounding_box
 
     if transform = attributes["gradientTransform"]
-      matrix = transform.split(COMMA_WSP_REGEXP).map(&:to_f)
-      if matrix != [1, 0, 0, 1, 0, 0]
-        raise SkipElementError, "prawn-svg does not yet support gradients with a non-identity gradientTransform attribute"
-      end
+      @transform_matrix = parse_transform_attribute(transform)
     end
 
     if (spread_method = attributes['spreadMethod']) && spread_method != "pad"

lib/prawn/svg/extensions/additional_gradient_transforms.rb

@@ -0,0 +1,23 @@
+module Prawn::SVG::Extensions
+  module AdditionalGradientTransforms
+    def gradient_coordinates(gradient)
+      # As of Prawn 2.2.0, apply_transformations is used as purely a boolean.
+      #
+      # Here we're using it to optionally pass in a 6-tuple transformation matrix that gets applied to the
+      # gradient.  This should be added to Prawn properly, and then this monkey patch will not be necessary.
+
+      if gradient.apply_transformations.is_a?(Array)
+        x1, y1, x2, y2, transformation = super
+        a, b, c, d, e, f = transformation
+        na, nb, nc, nd, ne, nf = gradient.apply_transformations
+
+        matrix = Matrix[[a, c, e], [b, d, f], [0, 0, 1]] * Matrix[[na, nc, ne], [nb, nd, nf], [0, 0, 1]]
+        new_transformation = matrix.to_a[0..1].transpose.flatten
+
+        [x1, y1, x2, y2, new_transformation]
+      else
+        super
+      end
+    end
+  end
+end

lib/prawn/svg/transform_parser.rb

@@ -0,0 +1,72 @@
+module Prawn::SVG::TransformParser
+  def parse_transform_attribute(transform)
+    matrix = Matrix.identity(3)
+
+    parse_css_method_calls(transform).each do |name, arguments|
+      case name
+      when 'translate'
+        x, y = arguments
+        matrix *= Matrix[[1, 0, x_pixels(x.to_f)], [0, 1, -y_pixels(y.to_f)], [0, 0, 1]]
+
+      when 'translateX'
+        x = arguments.first
+        matrix *= Matrix[[1, 0, x_pixels(x.to_f)], [0, 1, 0], [0, 0, 1]]
+
+      when 'translateY'
+        y = arguments.first
+        matrix *= Matrix[[1, 0, 0], [0, 1, -y_pixels(y.to_f)], [0, 0, 1]]
+
+      when 'rotate'
+        angle, x, y = arguments.collect { |a| a.to_f }
+        angle = angle * Math::PI / 180.0
+
+        case arguments.length
+        when 1
+          matrix *= Matrix[[Math.cos(angle), Math.sin(angle), 0], [-Math.sin(angle), Math.cos(angle), 0], [0, 0, 1]]
+        when 3
+          matrix *= Matrix[[1, 0, x_pixels(x.to_f)], [0, 1, -y_pixels(y.to_f)], [0, 0, 1]]
+          matrix *= Matrix[[Math.cos(angle), Math.sin(angle), 0], [-Math.sin(angle), Math.cos(angle), 0], [0, 0, 1]]
+          matrix *= Matrix[[1, 0, -x_pixels(x.to_f)], [0, 1, y_pixels(y.to_f)], [0, 0, 1]]
+        else
+          warnings << "transform 'rotate' must have either one or three arguments"
+        end
+
+      when 'scale'
+        x_scale = arguments[0].to_f
+        y_scale = (arguments[1] || x_scale).to_f
+        matrix *= Matrix[[x_scale, 0, 0], [0, y_scale, 0], [0, 0, 1]]
+
+      when 'skewX'
+        angle = arguments[0].to_f * Math::PI / 180.0
+        matrix *= Matrix[[1, -Math.tan(angle), 0], [0, 1, 0], [0, 0, 1]]
+
+      when 'skewY'
+        angle = arguments[0].to_f * Math::PI / 180.0
+        matrix *= Matrix[[1, 0, 0], [-Math.tan(angle), 1, 0], [0, 0, 1]]
+
+      when 'matrix'
+        if arguments.length != 6
+          warnings << "transform 'matrix' must have six arguments"
+        else
+          a, b, c, d, e, f = arguments.collect { |argument| argument.to_f }
+          matrix *= Matrix[[a, -c, e], [-b, d, -f], [0, 0, 1]]
+        end
+
+      else
+        warnings << "Unknown/unsupported transformation '#{name}'; ignoring"
+      end
+    end
+
+    matrix.to_a[0..1].transpose.flatten
+  end
+
+  private
+
+  def parse_css_method_calls(string)
+    string.scan(/\s*(\w+)\(([^)]+)\)\s*/).collect do |call|
+      name, argument_string = call
+      arguments = argument_string.strip.split(/\s*[,\s]\s*/)
+      [name, arguments]
+    end
+  end
+end

spec/prawn/svg/attributes/transform_spec.rb

@@ -14,43 +14,38 @@ def initialize
 
   let(:element) { TransformTestElement.new }
 
-  describe "#parse_transform_attribute_and_call" do
-    subject { element.send :parse_transform_attribute_and_call }
-
-    describe "translate" do
-      it "handles a missing y argument" do
-        expect(element).to receive(:add_call_and_enter).with('translate', -5.5, 0)
-        expect(element).to receive(:x_pixels).with(-5.5).and_return(-5.5)
-        expect(element).to receive(:y_pixels).with(0.0).and_return(0.0)
-
-        element.attributes['transform'] = 'translate(-5.5)'
-        subject
-      end
+  subject { element.send :parse_transform_attribute_and_call }
+
+  context "when a non-identity matrix is requested" do
+    let(:transform) { 'translate(-5.5)' }
+
+    it "passes the transform and executes the returned matrix" do
+      expect(element).to receive(:parse_transform_attribute).with(transform).and_return([1, 2, 3, 4, 5, 6])
+      expect(element).to receive(:add_call_and_enter).with('transformation_matrix', 1, 2, 3, 4, 5, 6)
+
+      element.attributes['transform'] = transform
+      subject
+    end
+  end
+
+  context "when an identity matrix is requested" do
+    let(:transform) { 'translate(0)' }
+
+    it "does not execute any commands" do
+      expect(element).to receive(:parse_transform_attribute).with(transform).and_return([1, 0, 0, 1, 0, 0])
+      expect(element).not_to receive(:add_call_and_enter)
+
+      element.attributes['transform'] = transform
+      subject
     end
+  end
+
+  context "when transform is blank" do
+    it "does nothing" do
+      expect(element).not_to receive(:parse_transform_attribute)
+      expect(element).not_to receive(:add_call_and_enter)
 
-    describe "rotate" do
-      it "handles a single angle argument" do
-        expect(element).to receive(:add_call_and_enter).with('rotate', -5.5, :origin => [0, 0])
-        expect(element).to receive(:y).with('0').and_return(0)
-
-        element.attributes['transform'] = 'rotate(5.5)'
-        subject
-      end
-
-      it "handles three arguments" do
-        expect(element).to receive(:add_call_and_enter).with('rotate', -5.5, :origin => [1.0, 2.0])
-        expect(element).to receive(:x).with(1.0).and_return(1.0)
-        expect(element).to receive(:y).with(2.0).and_return(2.0)
-
-        element.attributes['transform'] = 'rotate(5.5 1 2)'
-        subject
-      end
-
-      it "does nothing and warns if two arguments" do
-        expect(element).to receive(:warnings).and_return([])
-        element.attributes['transform'] = 'rotate(5.5 1)'
-        subject
-      end
+      subject
     end
   end
 end

spec/prawn/svg/elements/base_spec.rb

@@ -25,14 +25,14 @@
     describe "applying calls from the standard attributes" do
       let(:svg) do
         <<-SVG
-          <something transform="rotate(90)" fill-opacity="0.5" fill="red" stroke="blue" stroke-width="5"/>
+          <something transform="scale(2)" fill-opacity="0.5" fill="red" stroke="blue" stroke-width="5"/>
         SVG
       end
 
       it "appends the relevant calls" do
         element.process
         expect(element.base_calls).to eq [
-          ["rotate", [-90.0, {origin: [0, 600.0]}], [
+          ["transformation_matrix", [2, 0, 0, 2, 0, 0], [
             ["transparent", [0.5, 1], [
               ["fill_color", ["ff0000"], []],
               ["stroke_color", ["0000ff"], []],

spec/prawn/svg/elements/gradient_spec.rb

@@ -29,7 +29,8 @@
       expect(arguments).to eq(
         from: [100.0, 100.0],
         to:   [120.0, 0.0],
-        stops: [[0, "ff0000"], [0.25, "ff0000"], [0.5, "ffffff"], [0.75, "0000ff"], [1, "0000ff"]]
+        stops: [[0, "ff0000"], [0.25, "ff0000"], [0.5, "ffffff"], [0.75, "0000ff"], [1, "0000ff"]],
+        apply_transformations: true,
       )
     end
 
@@ -54,7 +55,30 @@
       expect(arguments).to eq(
         from: [100.0, 100.0],
         to:   [200.0, 0.0],
-        stops: [[0, "ff0000"], [1, "0000ff"]]
+        stops: [[0, "ff0000"], [1, "0000ff"]],
+        apply_transformations: true,
+      )
+    end
+  end
+
+  context "when gradientTransform is specified" do
+    let(:svg) do
+      <<-SVG
+        <linearGradient id="flag" gradientTransform="translateX(10) scale(2)" x1="0" y1="0" x2="10" y2="10">
+          <stop offset="0" stop-color="red"/>
+          <stop offset="1" stop-color="blue"/>
+        </linearGradient>
+      SVG
+    end
+
+    it "passes in the transform via the apply_transformations option" do
+      arguments = element.gradient_arguments(double(bounding_box: [0, 0, 10, 10]))
+
+      expect(arguments).to eq(
+        from: [0, 0],
+        to:   [10, 10],
+        stops: [[0, "ff0000"], [1, "0000ff"]],
+        apply_transformations: [2, 0, 0, 2, 10, 0],
       )
     end
   end