glsl shader generator for vertical blur with weights from Pascal Triangle

vertical_blur.glsl.rb

#!/usr/bin/env ruby

## first parameter is the row number from pascal triangle

def triangle(n)
    ret = []
    (0..n).each{|r|
            lst=[1]
            term=1
            k=1
            (0..r-1).step(1){|index|
                    term=term*(r-k+1)/k
                    lst.push term
                    k+=1
            }
            ret = lst
    }
    return ret
end

row = triangle(ARGV[0].to_i)
sum = row.reduce(:+).to_f
weights = row.map { |v| v / sum }
len = row.size


print    "vec2 uv = gl_TexCoord[0].xy;\n"
print    "vec4 sum = vec4( 0.0 );\n"
print    "float bs = blurSize / resolution.y;\n"

len.times do |i|
    offset = (i - (len-1)/2.0) / len
    printf "sum += texture2D(tex, vec2(uv.x, uv.y + bs * #{offset})) * #{weights[i]};\n"
end  

print   "gl_FragColor = sum;\n"