Raise error for colors with leading #

CHANGELOG.md

@@ -1,6 +1,14 @@
 
 ## PrawnPDF master branch
 
+### Validate colors passed in as strings must be valid hexadecimal
+
+Colors that were passed with a # would previously be misrepresented. Now
+any colors passed in as a string must be valid hexadecimal or they will
+raise an error.
+
+(Tom Prats, [#807](https://github.com/prawnpdf/prawn/issues/807), [#869](https://github.com/prawnpdf/prawn/issues/869))
+
 ### Added support for PNG images with indexed transparency
 
 Prawn now properly hadles transparency in PNG images with indexed color.

lib/prawn/graphics/color.rb

@@ -94,7 +94,11 @@ def process_color(*color)
       def color_type(color)
         case color
         when String
-          :RGB
+          if color =~ /\A[0-F]{6}\z/i
+            :RGB
+          else
+            fail ArgumentError, "Unknown type of color: #{color.inspect}"
+          end
         when Array
           case color.length
           when 3

manual/graphics/color.rb

@@ -10,7 +10,7 @@
 Prawn::ManualBuilder::Example.generate(filename) do
   stroke_axis
 
-  # Fill with Yellow using RGB
+  # Fill with Yellow using RGB (Unlike css, there is no leading #)
   fill_color "FFFFCC"
   fill_polygon [50, 150], [150, 200], [250, 150],
                [250, 50], [150, 0], [50, 50]

spec/graphics_spec.rb

@@ -237,6 +237,14 @@
     expect(colors.fill_color).to eq([0.8, 1.0, 0])
   end
 
+  it "should raise an error for a color with a leading #" do
+    expect { @pdf.fill_color "#ccff00" }.to raise_error(ArgumentError)
+  end
+
+  it "should raise an error for a color string that isn't a hex" do
+    expect { @pdf.fill_color "zcff00" }.to raise_error(ArgumentError)
+  end
+
   it "should reset the colors on each new page if they have been defined" do
     @pdf.fill_color "ccff00"