Returns a binary representation of a POSTNET encoded zip code, suitable for converting to an image

postnet_bin.rb

#returns binary representation of a POSTNET encoded zip code
#could be used to filter a zip code and then generate an image
#1 = full bar, 0 = half bar
class PostnetBin	
	def self.convert(zip)
		codes = ["11000","00011","00101","00110","01001","01010","01100","10001","10010","10100"]
		r = "1" #bookend
		total = 0
		zip.gsub(/[^\d]/,'').each_char do |c| 
			r += codes[c.to_i]
			total += c.to_i
		end
		
		#check digit
		#find sum of digits, get next highest number divisible by 10 
		#check digit is difference between that number and the original total
		check = (((total/10) + 1) * 10) - total
		r += codes[check]
		
		r + "1" #bookend
	end
end