SVG Weave/Crosshatching Pattern Generator

[Hai-Etlik]

A crosshatching type pattern that resembles weaving. I've seen it used in a few places and decided to make my own. And being lazy, I got the computer to do it for me by writing a Ruby script.

Here's the code.

require 'matrix'

class Vector
  def pair_mult(v)
    map2(v) do |x1, x2|
      x1*x2
    end
  end
end


BOX_SIZE=Vector[10,10]
BOX_COUNT=Vector[8,8]
BOX_SHIFT=Vector[1.5,1.5]
PATTERN_SIZE=BOX_SIZE.pair_mult(BOX_COUNT)
LINES=4


def moveto(p)
  "M #{p[0]} #{p[1]}"
end

def lineto(p)
  "L #{p[0]} #{p[1]}"
end



def envelope_lines(a,b,c,d,lines)
  step1=(b-a)*(1.0/(lines+1))
  step2=(d-c)*(1.0/(lines+1))

  result=[]
  
  lines.times do |i|
    result<< moveto(a+step1*(i+1))
    result<< lineto(c+step2*(i+1))
  end
  return result.join " "
end



points=Array.new(BOX_COUNT[1]) do |j|
  row=Array.new(BOX_COUNT[0]) do |i|

    Vector[i,j].pair_mult(BOX_SIZE)+Vector[2*rand-1, 2*rand-1].pair_mult(BOX_SHIFT)
  end
  row<< row[0]+Vector[PATTERN_SIZE[0],0] # Last point is the first point shifted by the width of the whole pattern
end
# Last row is the first row shifted by the height of the whole pattern
points<< points[0].map {|p| p+Vector[0,PATTERN_SIZE[1]]}

result=""

BOX_COUNT[1].times do |j|
  BOX_COUNT[0].times do |i|
    a=points[j][i]
    b=points[j][i+1]
    c=points[j+1][i]
    d=points[j+1][i+1]

    a,b,c,d=a,c,b,d if (i+j)%2==0 # Swap vertical and horizontal in alternating boxes

    result+=envelope_lines(a,b,c,d,LINES)
  end
end


puts <<EOS
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
  "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="4cm" height="4cm" viewBox="0 0 #{PATTERN_SIZE[0]} #{PATTERN_SIZE[1]} "
     xmlns="http://www.w3.org/2000/svg" version="1.1">
    <defs>
<pattern id="weave" patternUnits="userSpaceOnUse"
             x="0" y="0" width="#{PATTERN_SIZE[0]}" height="#{PATTERN_SIZE[1]}">
    <path stroke="black" d="#{result}" stroke-width="1" />
      
    </pattern> 
  </defs>
  <rect fill="url(#weave)" x="0" y="0" width="#{PATTERN_SIZE[0]}" height="#{PATTERN_SIZE[1]}" />
</svg>
EOS

The pattern itself is zipped because the forum is stupid.