Class: Code39

Inherits:
Object
  • Object
show all
Defined in:
lib/barcode/code39.rb

Overview

This class takes a string and generates a Code 39-based barcode from that string.

Constant Summary collapse

@@encoding =

quick reference as to what’s up with @@encoding:

  • B => large solid bar

  • b => small solid bar

  • W => large space

  • w => small space

{
   '0' => "bwbWBwBwb",
   '1' => "BwbWbwbwB",
   '2' => "bwBWbwbwB",
   '3' => "BwBWbwbwb",
   '4' => "bwbWBwbwB",
   '5' => "BwbWBwbwb",
   '6' => "bwBWBwbwb",
   '7' => "bwbWbwBwB",
   '8' => "BwbWbwBwb",
   '9' => "bwBWbwBwb",
   'A' => "BwbwbWbwB",
   'B' => "bwBwbWbwB",
   'C' => "BwBwbWbwb",
   'D' => "bwbwBWbwB",
   'E' => "BwbwBWbwb",
   'F' => "bwBwBWbwb",
   'G' => "bwbwbWBwB",
   'H' => "BwbwbWBwb",
   'I' => "bwBwbWBwb",
   'J' => "bwbwBWBwb",
   'K' => "BwbwbwbWB",
   'L' => "bwBwbwbWB",
   'M' => "BwBwbwbWb",
   'N' => "bwbwBwbWB",
   'O' => "BwbwBwbWb",
   'P' => "bwBwBwbWb",
   'Q' => "bwbwbwBWB",
   'R' => "BwbwbwBWb",
   'S' => "bwBwbwBWb",
   'T' => "bwbwBwBWb",
   'U' => "BWbwbwbwB",
   'V' => "bWBwbwbwB",
   'W' => "BWBwbwbwb",
   'X' => "bWbwBwbwB",
   'Y' => "BWbwBwbwb",
   'Z' => "bWBwBwbwb",
   '-' => "bWbwbwBwB",
   '.' => "BWbwbwBwb",
   ' ' => "bWBwbwBwb",
   '$' => "bWbWbWbwb",
   '/' => "bWbWbwbWb",
   '+' => "bWbwbWbWb",
   '%' => "bwbWbWbWb",
   '*' => "bWbwBwBwb"
}

Instance Method Summary collapse

Constructor Details

#initialize(text) ⇒ Code39

Takes a string, uppercases it, and wraps it in asterisks. If any character is unavailable in Code 39 encoding, throws a vicious error.



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# File 'lib/barcode/code39.rb', line 70

def initialize(text)
   text = text.upcase
   text.split(//).each do |char|
      if not @@encoding.has_key?(char)
         raise "Unencodable string."
      end
   end
   
   @text = "*#{text}*"
end

Instance Method Details

#to_img(filename, width, height) ⇒ Object

The overly complicated image generation code. Your barcode image width and height should be in pixels. The actual barcode will not be that width, instead it will be a multiple of your text string (plus two asterisks - @text) length * 14. White space will center the rest.



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# File 'lib/barcode/code39.rb', line 99

def to_img(filename, width, height)
   bar_code_width = width - (width % ( @text.length * 14 ) )
   letter_width = bar_code_width / @text.length
   small_bar_width = letter_width / 14
   large_bar_width = ((7.0 / 3.0) * small_bar_width.to_f).to_i
   
   canvas = Image.new(width, height)
   gc = Draw.new
   gc.fill('black')
   gc.stroke('black')
   gc.stroke_width(-1)
   # Necessary to prevent massive blurry image nonsense.
   gc.stroke_antialias(false)
   
   cur_x = (width - bar_code_width) / 2
   
   self.to_s.split(//).each do |char|
      if char.upcase == "B"
         gc.rectangle(cur_x, 0, cur_x + (char == "B" ? large_bar_width : small_bar_width), height)
      end
      cur_x += char.match(/[BW]/) ? large_bar_width : small_bar_width
   end
   gc.draw(canvas)
   canvas.write(filename)
end

#to_s ⇒ Object

Outputs a string that represents the encoding. Not necessarily useful externally, but who knows?



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# File 'lib/barcode/code39.rb', line 84

def to_s
   output = String.new()
   @text.split(//).each do |char|
      output += @@encoding[char] + " "
   end
   return output
end