From: Justin Ethier <justin.ethier@...>
Date: 2007-06-11T05:42:41+09:00
Subject: [QUIZ][SOLUTION] Mexican Blanket (#127)

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Hello,

Here is my solution to the quiz. Looking at the pattern for a moment, each
line of the pattern is really just the previous line, shifted over one
pixel. Thus to draw the pattern we can first calculate what all of the
pixels will be. Then we simply iterate over this list, drawing one line at a
time. With that in mind, here is the code I used to create the gradient:

def create_gradient(colors, width=5)
  pattern = []

  for i in 0...(width)
    (width-i).times { pattern.push(colors[0]) }
    (i+1).times { pattern.push(colors[1]) }
  end

  for i in 0...(width)
    (i+1).times { pattern.push(colors[2]) }
    (width-i-1).times { pattern.push(colors[1]) }
  end

  pattern
end

And this function creates solid bands of color:

def create_solid(colors, width)
  pattern = []
  for color in colors
    width.times { pattern.push(color) }
  end
  pattern
end

To draw ASCII we simply print each line in turn.

def draw_ascii(pattern, width)
  for i in 0...(pattern.size-width+1)
    puts pattern.slice(i, width).join
  end
end

And to draw a JPEG we get a bit fancier, but its the same basic idea. There
must be a better way to code this, because it takes much too long to run.
But anyway, here it is:

require 'RMagick'
include Magick

def draw(filename, pattern, width, height)
  canvas = Magick::ImageList.new
  canvas.new_image(width, height, Magick::HatchFill.new('white', 'white'))
  pts = Magick::Draw.new

  for y in 0... height
    line = pattern.slice(y, width)

    x = 0
    for color in line
      pts.fill(color)
      pts.point(x, y)
      x = x + 1
    end
  end

  pts.draw(canvas)
  canvas.write(filename)
end

Finally, we draw the ASCII from the Quiz and a picture similar to the one
that was posted.

# 1) Draw the ASCII representation
draw_ascii(create_gradient(['R', 'B', 'Y']), 28)

# 2) Draw a picture of the blanket
mex_flag = create_solid(['rgb(0, 64, 0)', 'white', 'red'], 5)
border = create_solid(['rgb(0, 64, 0)'], 25)

pattern = create_gradient(['red', 'blue', 'yellow'])
pattern = pattern + mex_flag
pattern = pattern + border
pattern = pattern + create_gradient(['black', 'red', 'orange'])
pattern = pattern + border
pattern = pattern + mex_flag.reverse
pattern = pattern + create_gradient(['red', 'purple', 'black'], 8)
draw("mexican_blanket.jpg", pattern, 100, 200)

Here is a picture of the final blanket, if anyone is interested:
http://justin.ethier.googlepages.com/mexican_blanket.jpg

Any thoughts? The code could probably be more clever, but I tried to make
everything as easy to follow as possible.
Thanks,

Justin

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