adding support for block canvas

Author: nanobowers

example/ex_canvases.rb

@@ -0,0 +1,9 @@
+#!/bin/env ruby
+$LOAD_PATH << "#{__dir__}/../lib"
+require "unicode_plot"
+
+# example of line plots using different canvases
+UnicodePlot.lineplot([1, 2, 7], [9, -6, 8], title: "Default Lineplot").render
+UnicodePlot.lineplot([1, 2, 7], [9, -6, 8], title: "Ascii Lineplot", canvas: :ascii).render
+UnicodePlot.lineplot([1, 2, 7], [9, -6, 8], title: "Dot Lineplot", canvas: :dot).render
+UnicodePlot.lineplot([1, 2, 7], [9, -6, 8], title: "Block Lineplot", canvas: :block).render

lib/unicode_plot.rb

@@ -13,6 +13,7 @@
 require 'unicode_plot/lookup_canvas'
 require 'unicode_plot/ascii_canvas'
 require 'unicode_plot/dot_canvas'
+require 'unicode_plot/block_canvas'
 
 require 'unicode_plot/plot'
 require 'unicode_plot/grid_plot'

lib/unicode_plot/block_canvas.rb

@@ -0,0 +1,38 @@
+# coding: utf-8
+
+=begin
+The `BlockCanvas` is also Unicode-based.
+It has half the resolution of the `BrailleCanvas`.
+In contrast to BrailleCanvas, the pixels don't
+have visible spacing between them.
+This canvas effectively turns every character
+into 4 pixels that can individually be manipulated
+using binary operations.
+=end
+
+module UnicodePlot
+  class BlockCanvas < LookupCanvas
+    X_PIXEL_PER_CHAR = 2
+    Y_PIXEL_PER_CHAR = 2
+
+    def initialize(width, height, fill_char=0, **kw)
+      super(width, height,
+            X_PIXEL_PER_CHAR,
+            Y_PIXEL_PER_CHAR,
+            fill_char,
+            **kw)
+    end
+    
+    BLOCK_SIGNS = [ [0b1000, 0b0010].freeze,
+                    [0b0100, 0b0001].freeze
+                  ].freeze
+
+    BLOCK_DECODE = [' ', '▗', '▖', '▄',
+                    '▝', '▐', '▞', '▟',
+                    '▘', '▚', '▌', '▙',
+                    '▀', '▜', '▛', '█' ].freeze
+
+    def lookup_encode(x,y) ; BLOCK_SIGNS[x][y] ; end
+    def lookup_decode(x) ; BLOCK_DECODE[x] ; end
+  end
+end

lib/unicode_plot/canvas.rb

@@ -12,6 +12,8 @@ def self.create(canvas_type, width, height, **kw)
         DensityCanvas.new(width, height, **kw)
       when :dot
         DotCanvas.new(width, height, **kw)
+      when :block
+        BlockCanvas.new(width, height, **kw)
       else
         raise ArgumentError, "unknown canvas type: #{canvas_type}"
       end