block_canvas.rb

# 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