gradient class that prints a color between blue and red with a step size of "resolution" (arg)

gradient.rb

require 'chunky_png'

class Gradient
  attr_accessor :resolution, :R0, :G0, :B0, :R1, :G1, :B1

  def initialize(start = 0x0000ff, stop = 0xff0000, resolution = 100)
    @resolution = Float(resolution)

    @R0 = (start & 0xff0000) >> 16;
    @G0 = (start & 0x00ff00) >> 8;
    @B0 = (start & 0x0000ff) >> 0;

    @R1 = (stop & 0xff0000) >> 16;
    @G1 = (stop & 0x00ff00) >> 8;
    @B1 = (stop & 0x0000ff) >> 0;
  end

  def gradient(step)
    r = interpolate(@R0, @R1, step);
    g = interpolate(@G0, @G1, step);
    b = interpolate(@B0, @B1, step);

    (((r << 8) | g) << 8) | b;
  end

  def interpolate(start, stop, step)
    if (start < stop)
      return (((stop - start) * (step / @resolution)) + start).round;
    else
      return (((start - stop) * (1 - (step / @resolution))) + stop).round;
    end
  end

  def actual_color min, max, value
    raise "value must be between min and max: #{min} <= #{value} <= #{max}" if value < min or value > max
    final = (@resolution * (value - min)).to_f/(max - min)
    gradient(final.round).to_s(16)
  end

  def hex_color min, max, value
    '#'+actual_color(min, max, value).rjust(6, '0')
  end

  def map_color min, max, value
    aux = actual_color(min, max, value).split('').each_cons(2).to_a
    "bb" + ([0, 2, 4].map{|it| aux[it].join }.reverse.join)
  end

end

grad = Gradient.new

colors = (1..100).map{ |c| grad.hex_color 1, 100, c }

# Creating an image from scratch, save as an interlaced PNG
png = ChunkyPNG::Image.new(100, 32, ChunkyPNG::Color::TRANSPARENT)
(0..99).each do |w|
  (0..31).each do |h|
    png[w,h] = ChunkyPNG::Color(colors[w])
  end
end

png.save('/tmp/output.png', :interlace => true)