RDoc fixes and spec additions to Canvas#initialize, now also raises A…

…rgumentError exceptions when the initial value is not understood.

lib/chunky_png/canvas.rb

@@ -58,20 +58,25 @@ class Canvas
     # CONSTRUCTORS
     #################################################################
 
-    # Initializes a new Canvas instance
-    # @param [Integer] width The width in pixels of this canvas
-    # @param [Integer] height The height in pixels of this canvas
-    # @param [ChunkyPNG::Pixel, Array<ChunkyPNG::Color>] initial The initial value of the pixels:
+    # Initializes a new Canvas instance.
     #
-    #    * If a color is passed to this parameter, this color will be used as background color.
+    # @overload initialize(width, height, background_color)
+    #   @param [Integer] width The width in pixels of this canvas
+    #   @param [Integer] height The height in pixels of this canvas
+    #   @param [Integer, ...] background_color The initial background color of this canvas.
+    #      This can be a color value or any value that {ChunkyPNG::Color.parse} can handle.
     #
-    #    * If an array of pixels is provided, these pixels will be used as initial value. Note
-    #      that the amount of pixels in this array should equal +width * height+.
+    # @overload initialize(width, height, initial)
+    #   @param [Integer] width The width in pixels of this canvas
+    #   @param [Integer] height The height in pixels of this canvas
+    #   @param [Array<Integer>] initial The initial pizel values. Must be an array with 
+    #     <tt>width * height</tt> elements.
     def initialize(width, height, initial = ChunkyPNG::Color::TRANSPARENT)
 
       @width, @height = width, height
 
-      if initial.kind_of?(Array) && initial.length == width * height
+      if initial.kind_of?(Array)
+        raise ArgumentError, "The initial array should have #{width}x#{height} = #{width*height} elements!" unless initial.length == width * height
         @pixels = initial
       else
         @pixels = Array.new(width * height, ChunkyPNG::Color.parse(initial))

lib/chunky_png/color.rb

@@ -622,7 +622,7 @@ def html_color(color_name, opacity = nil)
         base_color_name = $1.gsub(/[^a-z]+/i, '').downcase.to_sym
         return PREDEFINED_COLORS[base_color_name] | opacity if PREDEFINED_COLORS.has_key?(base_color_name)
       end
-      raise ChunkyPNG::Exception, "Unknown color name #{color_name}!"
+      raise ArgumentError, "Unknown color name #{color_name}!"
     end
 
     # @return [Integer] Black pixel/color

spec/chunky_png/canvas_spec.rb

@@ -8,6 +8,35 @@
   it { should respond_to(:height) }
   it { should respond_to(:pixels) }
 
+  describe '#initialize' do
+    it "should accept a single color value as background color" do
+      canvas = ChunkyPNG::Canvas.new(2, 2, 'red @ 0.8')
+      canvas[1, 0].should == ChunkyPNG::Color.parse('red @ 0.8')
+    end
+
+    it "should raise an error if the color value is not understood" do
+      lambda { ChunkyPNG::Canvas.new(2, 2, :nonsense) }.should raise_error(ArgumentError)
+    end
+
+    it "should accept an array as initial pixel values" do
+      canvas = ChunkyPNG::Canvas.new(2, 2, [1,2,3,4])
+      canvas[0, 0].should == 1
+      canvas[1, 0].should == 2
+      canvas[0, 1].should == 3
+      canvas[1, 1].should == 4
+    end
+
+    it "should raise an ArgumentError if the initial array does not have the correct number of elements" do
+      lambda { ChunkyPNG::Canvas.new(2, 2, [1,2,3]) }.should raise_error(ArgumentError)
+      lambda { ChunkyPNG::Canvas.new(2, 2, [1,2,3,4,5]) }.should raise_error(ArgumentError)      
+    end
+
+    it "should use a transparent background by default" do
+      canvas = ChunkyPNG::Canvas.new(1, 1)
+      canvas[0,0].should == ChunkyPNG::Color::TRANSPARENT
+    end
+  end
+
   describe '#dimension' do
     it "should return the dimensions as a Dimension instance" do
       subject.dimension.should == ChunkyPNG::Dimension('1x1')