Simple circle image generator for Ruby/Gosu

circle.rb

#! /usr/local/bin/ruby

require 'gosu'

class Circle
  attr_reader :columns, :rows
  
  def initialize(radius, colorR, colorG, colorB)
    @columns = @rows = radius * 2
    lower_half = (0...radius).map do |y|
      x = Math.sqrt(radius**2 - y**2).round
      right_half = "#{"#{colorR.chr}" * x}#{"#{0.chr}" * (radius - x)}"
      "#{right_half.reverse}#{right_half}"
    end.join
    blob0 = lower_half.reverse + lower_half
    blob0.gsub!(/./) { |alpha| "#{colorR.chr}#{colorG.chr}#{colorB.chr}#{alpha}"}
    lower_half = (0...radius).map do |y|
      x = Math.sqrt(radius**2 - y**2).round
      right_half = "#{"#{colorG.chr}" * x}#{"#{0.chr}" * (radius - x)}"
      "#{right_half.reverse}#{right_half}"
    end.join
    blob1 = lower_half.reverse + lower_half
    blob1.gsub!(/./) { |alpha| "#{colorR.chr}#{colorG.chr}#{colorB.chr}#{alpha}"}
    lower_half = (0...radius).map do |y|
      x = Math.sqrt(radius**2 - y**2).round
      right_half = "#{"#{colorB.chr}" * x}#{"#{0.chr}" * (radius - x)}"
      "#{right_half.reverse}#{right_half}"
    end.join
    blob2 = lower_half.reverse + lower_half
    blob2.gsub!(/./) { |alpha| "#{colorR.chr}#{colorG.chr}#{colorB.chr}#{alpha}"}
    if colorB > 0
      @blob = blob2
    elsif colorG > 0
      @blob = blob1
    else
      @blob = blob0
    end
    puts @blob.inspect
  end
  
  def to_blob
    @blob
  end
end

if __FILE__ == $0

  class TestWin < Gosu::Window
    def initialize(r, g, b)
      super 400, 400, false
    
      @img = Gosu::Image.new(self, Circle.new(50, r, g, b), false)
    end

    def draw
      @img.draw 0, 0, 0
    end
  end

  r = gets.to_i
  g = gets.to_i
  b = gets.to_i

  TestWin.new(r, g, b).show
end