From: Jesse Merriman <jesse.d.merriman@...>
Date: 2007-06-10T23:28:01+09:00
Subject: [SOLUTION][QUIZ] Mexican Blanket (#127)

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My solution builds a color string long enough to run across the top of the
blanket, turn, and run down the right side. This is shifted left for every
row. You can visualize the blanket as being a rectangular window on the
parallelogram that is created, like this for 10x5:

    [--------]
    xxxxxxxxxxxxxx
   xxxxxxxxxxxxxx
  xxxxxxxxxxxxxx
 xxxxxxxxxxxxxx
xxxxxxxxxxxxxx
    [--------]

Building the edge string is done mainly by my Blanket.edge method, which
repeatedly chooses a random color to gradient with the previous color.
Blanket.symmetrical_edge can create pattern-and-color symmetrical edges
by creating a half-length edge and flipping it, or pattern-but-not-color
symmetrical edges by doing this and mapping the colors to random colors.

I was able to re-use some of my code from Quiz 125 (fractals) to create
images with RMagick.

Examples:

$ ./mexican_blanket.rb 60 15
OOOOOOWOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRR
OOOOOWOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRW
OOOOWOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWW
OOOWOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWW
OOWOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWW
OWOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWR
WOOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRR
OOOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRR
OOOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRR
OOOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRRW
OOWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRRWW
OWWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRRWWW
WWOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRRWWWR
WOOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRRWWWRR
OOOOWWWOOOWWWWOOWWWWWOWWWWWWWRWWWWWWRRWWWWWRRRWWWWRRRRWWWRRR

$ # Blanket displayed on screen:
$ ./mexican_blanket.rb 300 400 --format display

$ ./mexican_blanket.rb 20 5 --symmetric
GGGGGGGGOGGGYYYRYYYY
GGGGGGGOGGGYYYRYYYYY
GGGGGGOGGGYYYRYYYYYY
GGGGGOGGGYYYRYYYYYYY
GGGGOGGGYYYRYYYYYYYY

$ ./mexican_blanket.rb 20 5 --color-symmetric
OOOOOROOOORRRROOOORO
OOOOROOOORRRROOOOROO
OOOROOOORRRROOOOROOO
OOROOOORRRROOOOROOOO
OROOOORRRROOOOROOOOO

$ ./mexican_blanket.rb 400 600 --format png
Wrote blanket to blanket_400x600.png

An example of that last one can be seen here:
http://www.jessemerriman.com/images/ruby_quiz/127_mexican_blanket/blanket_400x600.png

The full usage statement is at the top of mexican_blanket.rb

If you want to change the colors or stripe widths, its hard-coded at the top
of the Blanket class, and for graphics at the top of BlanketDraw.


-- 
Jesse Merriman
jessemerriman@warpmail.net
http://www.jessemerriman.com/

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# Ruby Quiz 127: Mexican Blanket
# blanket_draw.rb

require 'blanket'
require 'RMagick'

class BlanketDraw < Magick::Draw
  # Colors from http://library.thinkquest.org/05aug/01280/Images/flag.jpg
  # Not sure how accurate that is though..
  StringToColor = { 'R' => '#fe0000', 'B' => '#0333a1', 'Y' => '#ffff49',
                    'O' => '#ea6520', 'G' => '#039e36', 'W' => '#ffffff' }

  def initialize blanket
    super()
    fill_opacity 1
    stroke_width 1
    draw_blanket blanket
    self
  end

  def draw_blanket blanket
    # Filling in it point by point is kinda slow. Perhaps it'd be better to
    # find the coords of the diagonals and call line().
    blanket.each_row_with_index do |row, y|
      row.split(//).each_with_index do |color_char, x|
        fill StringToColor[color_char]
        point x, y
      end
    end
  end
end

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# Ruby Quiz 127: Mexican Blanket
# blanket_image.rb

require 'blanket'
require 'blanket_draw'
require 'RMagick'

class BlanketImage < Magick::Image
  def initialize blanket
    draw = BlanketDraw.new blanket
    super(blanket.width, blanket.height)
    draw.draw self
    self
  end
end

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#!/usr/bin/env ruby
# Ruby Quiz 127: Mexican Blanket
# mexican_blanket.rb

class Array
  # Pick a random element.
  def pick; self[rand(size)]; end
end

class Hash
  # Creates a hash from an array of pairs.
  # Doesn't something like this already exist?
  def Hash.from_pairs pairs
    h = {}
    pairs.each { |pair| h[pair.first] = pair.last }
    h
  end
end

class Blanket
  Colors = %w{R B O Y G W}
  StripeWidths = { :small => (1..1), :large => (5..10) }

  attr_reader :width, :height

  def initialize width, height, symmetrical = false, color_symmetrical = false
    @width, @height = width, height
    length = width + height - 1

    # Build upper-and-right edge.
    if symmetrical
      e = Blanket.symmetrical_edge length, color_symmetrical
    else
      e = Blanket.edge length
    end

    # Build @rows as an array of color strings.
    @rows = []
    (0...height).each do |shift|
      @rows << e[shift...width+shift]
    end

    self
  end

  def to_s; @rows.join("\n"); end

  def each_row; @rows.each { |r| yield(r) }; end
  def each_row_with_index; @rows.each_with_index { |r,i| yield(r,i) }; end

  # Return a random small stripe width and a random large stripe width.
  def Blanket.random_stripe_widths
    smin, smax = StripeWidths[:small].min, StripeWidths[:small].max
    lmin, lmax = StripeWidths[:large].min, StripeWidths[:large].max
    [rand(smax - smin + 1) + smin, rand(lmax - lmin + 1) + lmin]
  end

  # Return a random hash mapping colors to other colors.
  def Blanket.random_color_map
    Hash.from_pairs Colors.zip(Colors.sort_by { rand })
  end

  # Get an edge suitable for the upper-turning-the-corner-down-the-right-side
  # edge of the blanket as a string of color chars.
  # - length: the length of the edge (for the blanket: width + height - 1)
  def Blanket.edge length
    e = ''

    # Continually add gradients to e until we're too long, then chop off the
    # excess. Maybe not the best way to do it, but it works.
    c1 = Colors.pick
    while e.length < length
      c2 = (Colors - [c1]).pick
      small_width, large_width = random_stripe_widths

      # Add gradient of c1 -> c2
      large_width.downto(small_width+1) do |w|
        e += c1 * w + c2 * (large_width - w + 1)
      end
      e += c1 * small_width

      c1 = c2
    end

    e[0...length]
  end

  # Like edge, but with a symmetrical pattern.
  # - sym_colors: Colors should also be symmetrical.
  def Blanket.symmetrical_edge length, sym_colors = false
    parts = [edge(length/2)]
    parts << Colors.pick if (length % 2) == 1 # random center color

    if sym_colors
      parts << parts.first.reverse
    else
      color_map = random_color_map
      parts << parts.first.reverse.split(//).map { |char| color_map[char] }
    end

    parts.join
  end
end

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#!/usr/bin/env ruby
# Ruby Quiz 127: Mexican Blanket
# mexican_blanket.rb
#
# Usage: mexican_blanket.rb WIDTH HEIGHT [--symmetric | --color-symmetric]
#                                        [--format FORMAT]
#
# WIDTH:  The width of the blanket.
# HEIGHT: The height of the blanket.
# --symmetric:       The blanket should be pattern-but-not-color-symmetric.
# --color-symmetric: The blanket should be pattern-and-color-symmetric.
#
# Formats (default: text):
#   text:       Print out a textual representation of the blanket.
#   display:    Use RMagick to display the image.
#   IMG_FORMAT: An image format like png, jpg, or gif that RMagick understands.

require 'blanket'

if __FILE__ == $0
  width, height = ARGV[0].to_i, ARGV[1].to_i

  if ARGV.include? '--symmetric'
    blanket = Blanket.new(width, height, true, false)
  elsif ARGV.include? '--color-symmetric'
    blanket = Blanket.new(width, height, true, true)
  else
    blanket = Blanket.new(width, height)
  end

  i = ARGV.index '--format'
  format = (i.nil? ? 'text' : ARGV[i+1])

  if format == 'text'
    puts blanket
  else
    require 'blanket_image'
    image = BlanketImage.new blanket
    if format == 'display'
      image.display
    else
      begin
        filename = "blanket_#{width}x#{height}.#{format}"
        image.write filename
        puts "Wrote blanket to #{filename}"
      rescue Exception => ex
        $stderr.puts "There was an error writing the image to #{filename}"
        $stderr.puts "Are you sure the format '#{format}' is valid?"
        $stderr.puts "(#{ex})"
      end
    end
  end
end

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