Easy Gbarcode

A few posts ago I had mentioned that my Gbarcode project should really be a bit more user friendly as well as provide an easy way to create PNGs without loading memory hogging libraries like RMagick. I investigated using the Cairo libraries for this here.

Good news for every one that uses Gbarcode, and those thinking of using it, I created a small wrapper module that is more Ruby-ish and also uses Cairo to print out to PNG. The functionality is bare-bones, with a fixed height of 150 pixels and width is determined by the length of the encoded barcode. It works well for Code 128 barcodes. Grab the ruby file here.

To use this module, here is an example (note that bad encoding schemes will result in a raised excpetion, hence the begin/rescue block):

require 'gbc'
require 'gbarcode'
require 'markaby'

begin
b = GBC::Barcode.new(ARGV[0], Gbarcode::BARCODE_ANY)
puts b.ascii, b.partial, b.encoding
b.to_png("out.png")
b = Markaby::Builder.new()
b.html do
body do
img(:src => "out.png")
end
end
f = File.open("out.html","w")
f.write(b.to_s)
f.close
rescue Exception => e
puts e.message
end


Cairo for barcodes

Continuing my discussion about Gbarcode 2, I tested my theory of using Cairo for creation of barcodes. It turns out that this is not so hard, but it was a bit of a lerning curve, to say the least. I used the ruby DL library to load the cairo shared libs from the system (thanks to the GD2 gem for the code hints here). A few small methods where all that were needed for bare minimum functionality: creating bars and adding text. No fancy formating here.

Next, I used gnu barcode to get layout information for a barcode, so I could test the drawing methods independently of barcode creation logic.

The result is the picture posted above. Neat huh? Code is posted below, but I think for a production gem, I'll probably not use DL, since I have to wrap the gnu C libs for actually creating barcodes from text strings anyway.

Without further ado, the test script:

require 'dl'
require 'rbconfig'

module BC
VERSION = '1.5.0'.freeze

def self.cairo_library_name
case Config::CONFIG['arch']
when /darwin/
  'libcairo.2.dylib'
when /mswin32/, /cygwin/
  'cairo.dll'
else
  'libcairo.so.2'
end
end
def self.name_for_symbol(symbol, signature)
case Config::CONFIG['arch']
when /mswin32/, /cygwin/
  sum = -4
  signature.each_byte do |char|
    sum += case char
    when ?D: 8
    else     4
    end
  end
  "#{symbol}@#{sum}"
else
  symbol.to_s
end
end

private_class_method :cairo_library_name, :name_for_symbol

LIB = DL.dlopen(cairo_library_name)
SYM = {
:cairo_image_surface_create   => 'PIII',
:cairo_create    => 'PP',
:cairo_get_target    => 'PP',
:cairo_destroy    => '0P',
:cairo_surface_destroy    => '0P',
:cairo_surface_write_to_png    => '0PS',
:cairo_set_source_rgb    => '0PDDD',
:cairo_move_to    => '0PDD',
:cairo_line_to    => '0PDD',
:cairo_set_line_width    => '0PD',
:cairo_stroke    => '0P',
:cairo_select_font_face    => '0PSII',
:cairo_set_font_size    => '0PD',
:cairo_show_text    => '0PS'
}.inject({}) { |x, (k, v)| x[k] = LIB[name_for_symbol(k, v), v]; x }

class LibraryError < rs =" SYM[:cairo_image_surface_create].call(0,w,h)" rs =" SYM[:cairo_create].call(s)"> #{s.class}] :: R[#{r} =>  #{r.class}] :: RS[#{rs} =>  #{rs.class}]"
  SYM[:cairo_set_source_rgb].call(r,0.0,0.0,0.0)
  puts "S [#{s} => #{s.class}] :: R[#{r} =>  #{r.class}] :: RS[#{rs} =>  #{rs.class}]"
  return r
end

def self.ctx w,h
  context(surface(w,h))
end

def self.add_bar ctx,x,y,w,h
  # cairo_move_to(cr,11.0,20.5);
  # cairo_line_to(cr,11.0,70.5);
  # cairo_set_line_width(cr,1.85);
  # cairo_stroke(cr);
  SYM[:cairo_move_to].call(ctx,x,y)
  SYM[:cairo_line_to].call(ctx,x,h)
  SYM[:cairo_set_line_width].call(ctx,w)
  SYM[:cairo_stroke].call(ctx)
end

def self.add_text(ctx,txt,x,y)
  # cairo_select_font_face (cr, "serif", CAIRO_FONT_SLANT_NORMAL = 0, CAIRO_FONT_WEIGHT_BOLD = 1);
  # cairo_set_font_size (cr, 12.0);
  # cairo_move_to (cr, 21.0, 90.0);
  # cairo_show_text (cr, "TEST1234");  
  SYM[:cairo_select_font_face].call(ctx,"serif",0,1)
  SYM[:cairo_set_font_size].call(ctx,12.0)
  SYM[:cairo_move_to].call(ctx,x,y)
  SYM[:cairo_show_text].call(ctx,txt)
end

def self.draw(ctx,fname)
  # surface = cairo_get_target(cr)
  # cairo_destroy(cr);
  # cairo_surface_write_to_png (surface, "hello.png");
  # cairo_surface_destroy (surface);
  r,rs = SYM[:cairo_get_target].call(ctx)
  SYM[:cairo_destroy].call(ctx);
  SYM[:cairo_surface_write_to_png].call(r,fname)
  SYM[:cairo_surface_destroy].call(r);
end
end
end

include BC
c = B.ctx 132, 100

B.add_bar(c,  11.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  13.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  16.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  22.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  25.50 , 20.00,  2.85, 70.0)
B.add_bar(c,  30.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  32.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  37.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  39.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  44.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  47.50 , 20.00,  2.85, 70.0)
B.add_bar(c,  50.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  55.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  58.50 , 20.00,  2.85, 70.0)
B.add_bar(c,  63.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  65.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  68.50 , 20.00,  2.85, 70.0)
B.add_bar(c,  73.00 , 20.00,  3.85, 70.0)
B.add_bar(c,  76.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  79.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  83.50 , 20.00,  2.85, 70.0)
B.add_bar(c,  87.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  91.50 , 20.00,  0.85, 70.0)
B.add_bar(c,  94.00 , 20.00,  1.85, 70.0)
B.add_bar(c,  99.50 , 20.00,  2.85, 70.0)
B.add_bar(c, 103.00 , 20.00,  1.85, 70.0)
B.add_bar(c, 105.50 , 20.00,  0.85, 70.0)
B.add_bar(c, 110.00 , 20.00,  1.85, 70.0)
B.add_bar(c, 115.50 , 20.00,  2.85, 70.0)
B.add_bar(c, 118.50 , 20.00,  0.85, 70.0)
B.add_bar(c, 121.00 , 20.00,  1.85, 70.0)


B.add_text(c,"TEST1234", 21.0, 90.0)
B.draw(c,"test_bc.png")

Gbarcode using GD script

BTW, here is the script I used to create the barcode in the previous post using the gbarcode and gd2 gems:

require 'rubygems'
require 'gd2'
require 'gbarcode'

include Gbarcode
include GD2

b = barcode_create("TEST1234567890")
barcode_encode(b,BARCODE_128)

w = 20
h = 100
x = 10

y1 = 10
y2 = h - 20

bars = b.partial.split(//).map {|e| e.to_i}
bars.map {|e| w += e}

i = Image::IndexedColor.new(w,h)
i.palette << c =" Canvas.new(i)" color =" Color::BLACK" font =" Font::Small" f =" File.open(">

For the public good

For a while now, I have been working on designing data standards for the research community. Often times, the standards process is not so much based on efficient and useful design, but more on compromises between a large and diverse set of users. So far this process has led to complex standards that I have to take some partial credit for. Frankly I would rather not, but a publication record is a must for any sort of success at academic institutions.

But something good did came out of my dissatisfaction in the public contributions I have made thus far. I was motivated to contribute something to the open source community that was completely unrelated to data standards, a barcode creation library ( a gem) for ruby, Gbarcode. Several items helped in deciding that this would be a good project:

• I needed to create barcodes for a project ;)
  
• the existing ruby barcode gem only produced Code 39
• the images that it produced were not readable by my scanner
• the project was dead (last release was in July 2005)
  

I looked around and the current open source projects where GNU barcode (C), and Barbecue (Java). I decided to try my hand at SWIG wrapping the GNU barcode C API. Long story short, SWIG is not the most intuitive tool, but I was able to make some strides in creating the interface file and pass in Ruby strings to create the barcodes with.

One major hurdle of the project was creating a MS Windows-compatible gem. Gems are notorious for not supporting Windows. On Unix, Linux and Mac OS X, the gems usually install just fine, since they are compiled on install. On Windows, it is not at all straight forward to pre-compiling the parts of the library written in C. Since I wanted this to be useful for the widest audience, I looked around for other gems that did support Windows and found that Hpricot has a nice rake task and environment for compiling and packaging the gem for windows. Thanks to _why I was able to make this work, with a bit of leg work. I wouldn't recommend going to the SVN repos to look at what I did, since it is in an unstable state. Just go to _why's site and look at what he did.

One criticism I have with Gbarcode is that the only supported output format is PostScript. In order to use it for web sites (specifically RoR), you would have to run the output through ImageMagick, or some other image processing software. Much to my pleasant surprise, I looked the other day on Google, and several sites have covered how to do this. Just search for ruby and barcode and it should come right up.

The drawback to the approaches listed in those how-to's is that RMagick (and ImageMagick) are memory hogs. Since people are actually starting to use Gbarcode, I have started thinking about re-coding it it to make it more Ruby-ish (currently since it is a binding of the C lib, it uses C-style method calls) and to use Cairo as the image producing library. I tried GD, but the barcodes come out less than optimal:

I don't know why the bottom part of the barcode marges bars, maybe it happens on the way to encoding the PNG, but nothing I tried fixes this. My hope is that with the Cairo integration, this artifact goes away.