Provided by: libbarcode-code128-perl_2.21-3_all bug

NAME

       Barcode::Code128 - Generate CODE 128 bar codes

SYNOPSIS

         use Barcode::Code128;

         $code = new Barcode::Code128;

REQUIRES

       Perl 5.004, Carp, Exporter, GD (optional)

EXPORTS

       By default, nothing.  However there are a number of constants that represent special
       characters used in the CODE 128 symbology that you may wish to include.  For example if
       you are using the EAN-128 or UCC-128 code, the string to encode begins with the FNC1
       character.  To encode the EAN-128 string "00 0 0012345 555555555 8", you would do the
       following:

         use Barcode::Code128 'FNC1';
         $code = new Barcode::Code128;
         $code->text(FNC1.'00000123455555555558');

       To have this module export one or more of these characters, specify them on the "use"
       statement or use the special token ':all' instead to include all of them.  Examples:

         use Barcode::Code128 qw(FNC1 FNC2 FNC3 FNC4 Shift);
         use Barcode::Code128 qw(:all);

       Here is the complete list of the exportable characters.  They are assigned to high-order
       ASCII characters purely arbitrarily for the purposes of this module; the values used do
       not reflect any part of the CODE 128 standard.  Warning: Using the "CodeA", "CodeB",
       "CodeC", "StartA", "StartB", "StartC", and "Stop" codes may cause your barcodes to be
       invalid, and be rejected by scanners.  They are inserted automatically as needed by this
       module.

         CodeA      0xf4        CodeB      0xf5         CodeC      0xf6
         FNC1       0xf7        FNC2       0xf8         FNC3       0xf9
         FNC4       0xfa        Shift      0xfb         StartA     0xfc
         StartB     0xfd        StartC     0xfe         Stop       0xff

DESCRIPTION

       Barcode::Code128 generates bar codes using the CODE 128 symbology.  It can generate images
       in PNG or GIF format using the GD package, or it can generate a text string representing
       the barcode that you can render using some other technology if desired.

       The intended use of this module is to create a web page with a bar code on it, which can
       then be printed out and faxed or mailed to someone who will scan the bar code.  The
       application which spurred its creation was an expense report tool, where the employee
       submitting the report would print out the web page and staple the receipts to it, and the
       Accounts Payable clerk would scan the bar code to indicate that the receipts were
       received.

       The default settings for this module produce a large image that can safely be FAXed
       several times and still scanned easily.  If this requirement is not important you can
       generate smaller image using optional parameters, described below.

       If you wish to generate images with this module you must also have the GD module (written
       by Lincoln Stein, and available from CPAN) installed.  Using the libgd library, GD can
       generate files in PNG (Portable Network Graphics) or GIF (Graphic Interchange Format)
       formats.

       Starting with version 1.20, and ending with 2.0.28 (released July 21st, 2004), GD and the
       underlying libgd library could not generate GIF files due to patent issues, but any modern
       version of libgd (since 2004) can do GIF as the patent has expired.  Most browsers have no
       trouble with PNG files.

       In order to ensure you have a sufficiently modern installation of the GD module to do both
       GIF and PNG formats, we require version 2.18 of GD (which in turn requires libgd 2.0.28)
       or higher.

       If the GD module is not present, you can still use the module, but you will not be able to
       use its functions for generating images.  You can use the barcode() method to get a string
       of "#" and " " (hash and space) characters, and use your own image-generating routine with
       that as input.

       To use the the GD module, you will need to install it along with this module.  You can
       obtain it from the CPAN (Comprehensive Perl Archive Network) repository of your choice
       under the directory "authors/id/LDS".  Visit http://www.cpan.org/ for more information
       about CPAN.  The GD home page is: http://stein.cshl.org/WWW/software/GD/GD.html

METHODS

       new Usage:

               $object = new Barcode::Code128

           Creates a new barcode object.

       option
           Sets or retreives various options.  If called with only one parameter, retrieves the
           value for that parameter.  If called with more than one parameter, treats the
           parameters as name/value pairs and sets those option values accordingly.  If called
           with no parameters, returns a hash consisting of the values of all the options (hash
           ref in scalar context).  When an option has not been set, its default value is
           returned.

           You can also set or retrieve any of these options by using it as a method name.  For
           example, to set the value of the padding option, you can use either of these:

               $barcode->padding(10);
               $barcode->option("padding", 10);

           The valid options, and the default value and meaning of each, are:

               width            undef    Width of the image (*)
               height           undef    Height of the image (*)
               border           2        Size of the black border around the barcode
               scale            2        How many pixels for the smallest barcode stripe
               font             "large"  Font (**) for the text at the bottom
               show_text        1        True/False: display the text at the bottom?
               font_margin      2        Pixels above, below, and to left of the text
               font_align       "left"   Align the text ("left", "right", or "center")
               transparent_text 1/0(***) True/False: use transparent background for text?
               top_margin       0        No. of pixels above the barcode
               bottom_margin    0        No. of pixels below the barcode (& text)
               left_margin      0        No. of pixels to the left of the barcode
               right_margin     0        No. of pixels to the right of the barcode
               padding          20       Size of whitespace before & after barcode

           * Width and height are the default values for the $x and $y arguments to the png, gif,
           or gd_image method (q.v.)

           ** Font may be one of the following: "giant", "large", "medium", "small", or "tiny".
           Or, it may be any valid GD font name, such as "gdMediumFont".

           *** The "transparent_text" option is "1" (true) by default for GIF output, but "0"
           (false) for PNG.  This is because PNG transparency is not supported well by many
           viewing software The background color is grey (#CCCCCC) when not transparent.

       gif
       png
       gd_image
           Usage:

               $object->png($text)
               $object->png($text, $x, $y)
               $object->png($text, { options... })

               $object->gif($text)
               $object->gif($text, $x, $y)
               $object->gif($text, { options... })

               $object->gd_image($text)
               $object->gd_image($text, $x, $y)
               $object->gd_image($text, { options... })

           These methods generate an image using the GD module.  The gd_image() method returns a
           GD object, which is useful if you want to do additional processing to it using the GD
           object methods.  The other two create actual images.  NOTE: GIF files require an old
           version of GD, and so you probably are not able to create them - see below.

           The gif() and png() methods are wrappers around gd_image() that create the GD object
           and then run the corresponding GD method to create output that can be displayed or
           saved to a file.  Note that only one of these two methods will work, depending on
           which version of GD you have - see below.  The return value from gif() or png() is a
           binary file, so if you are working on an operating system (e.g. Microsoft Windows)
           that makes a distinction between text and binary files be sure to call
           binmode(FILEHANDLE) before writing the image to it, or the file may get corrupted.
           Example:

             open(PNG, ">code128.png") or die "Can't write code128.png: $!\n";
             binmode(PNG);
             print PNG $object->png("CODE 128");
             close(PNG);

           If you have GD version 1.20 or newer, the PNG file format is the only allowed option.
           Conversely if you have GD version prior to 1.20, then the GIF format is the only
           option.  Check the $object->image_format() method to find out which you have (q.v.).

           Note: All of the arguments to this function are optional.  If you have previously
           specified $text to the "barcode()", "encode()", or "text()" methods, you do not need
           to specify it again.  The $x and $y variables specify the size of the barcode within
           the image in pixels.  If size(s) are not specified, they will be set to the minimum
           size, which is the length of the barcode plus 40 pixels horizontally, and 15% of the
           length of the barcode vertically.  See also the $object->width() and $object->height()
           methods for another way of specifying this.

           If instead of specifying $x and $y, you pass a reference to a hash of name/value
           pairs, these will be used as the options, overriding anything set using the
           $object->option() (or width/height) method (q.v.).  However, this will not set the
           options so any future barcodes using the same object will revert to the option list of
           the object.  If you want to set the options permanently use the option, width, and/or
           height methods instead.

       barcode
           Usage:

               $object->barcode($text)

           Computes the bar code for the specified text.  The result will be a string of '#' and
           space characters representing the dark and light bands of the bar code.  You can use
           this if you have an alternate printing system besides using GD to create the images.

           Note: The $text parameter is optional. If you have previously specified $text to the
           "encode()" or "text()" methods, you do not need to specify it again.

   Housekeeping Functions
       The rest of the methods defined here are only for internal use, or if you really know what
       you are doing.  Some of them may be useful to authors of classes that inherit from this
       one, or may be overridden by subclasses.  If you just want to use this module to generate
       bar codes, you can stop reading here.

       encode
           Usage:

               $object->encode
               $object->encode($text)
               $object->encode($text, $preferred_code)

           Do the encoding.  If $text is supplied, will automatically call the text() method to
           set that as the text value first.  If $preferred_code is supplied, will try that code
           first.  Otherwise, the codes will be tried in the following manner:

           1. If it is possible to use Code C for any of the text, use that for as much of it as
           possible.

           2. Check how many characters would be converted using codes A or B, and use that code
           to convert them.  If the amount is equal, code A is used.

           3. Repeat steps 1 and 2 until the text string has been completely encoded.

       text
           Usage:

               $object->text($text)
               $text = $object->text

           Set or retrieve the text for this barcode.  This will be called automatically by
           encode() or barcode() so typically this will not be used directly by the user.

       start
           Usage:

               $object->start($code)

           If the code (see code()) is already defined, then adds the CodeA, CodeB, or CodeC
           character as appropriate to the encoded message inside the object.  Typically for
           internal use only.

       stop
           Usage:

               $object->stop()

           Computes the check character and appends it along with the Stop character, to the
           encoded string.  Typically for internal use only.

       code
           Usage:

               $object->code($code)
               $code = $object->code

           Set or retrieve the code for this barcode.  $code may be 'A', 'B', or 'C'.  Typically
           for internal use only.  Not particularly meaningful unless called during the middle of
           encoding.

CLASS VARIABLES

       None.

DIAGNOSTICS

       Unrecognized option ($opt) for $class
           The specified option is not valid for the module.  $class should be "Barcode::Code128"
           but if it has been inherited into another module, that module will show instead.  $opt
           is the attempted option.

       The gd_image() method of Barcode::Code128 requires the GD module
           To call the "gd_image()", "png()", or "gif()" methods, the GD module must be present.
           This module is used to create the actual image.  Without it, you can only use the
           "barcode()" method.

       Scale must be a positive integer
           The scale factor for the "gd_image()", "png()", or "gif()" methods must be a positive
           integer.

       Border ($border) must be a positive integer or zero
           The border option cannot be a fractional or negative number.

       Invalid font $font
           The specified font is not valid.  Note that this is tested using GD->can(), and so any
           subroutine in GD.pm will pass this test - but only the fonts will actually work.  See
           the GD module documentation for more.

       Image width $x is too small for bar code
           You have specified an image width that does not allow enough space for the bar code to
           be displayed.  The minimum allowable is the size of the bar code itself plus 40
           pixels.  If in doubt, just omit the width value when calling "gd_image()", "png()", or
           "gif()" and it will use the minimum.

       Image height $y is too small for bar code
           You have specified an image height that does not allow enough space for the bar code
           to be displayed.  The minimum allowable is 15% of the width of the bar code.  If in
           doubt, just omit the height value when calling "gd_image()", "png()", or "gif()" and
           it will use the minimum.

       Unable to create $x x $y image
           An error occurred when initializing a GD::Image object for the specified size.
           Perhaps $x and $y are too large for memory?

       The gif() method of Barcode::Code128 requires the GD module
       The gif() method of Barcode::Code128 requires version less than 1.20 of GD
       The png() method of Barcode::Code128 requires the GD module
       The png() method of Barcode::Code128 requires at least version 1.20 of GD
           These errors indicate that the GD module, or the correct version of the GD module for
           this method, was not present.  You need to install GD version 1.20 or greater to
           create PNG files, or a version of GD less than 1.20 to create GIF files.

       No encoded text found
           This message from "barcode()" typically means that there was no text message supplied
           either during the current method call or in a previous method call on the same object.
           This error occurs when you are trying to create a barcode by calling one of
           "gd_image()", "png()", "gif()", or "barcode()" without having specified the text to be
           encoded.

       No text defined
           This message from "encode()" typically means that there was no text message supplied
           either during the current method call or in a previous method call on the same object.

       Invalid preferred code ``$preferred_code''
           This error means "encode()" was called with the $preferred_code optional parameter but
           it was not one of ``A'', ``B'', or ``C''.

       Sanity Check Overflow
           This is a serious error in "encode()" that indicates a serious problem attempting to
           encode the requested message.  This means that an infinite loop was generated.  If you
           get this error please contact the author.

       Unable to find encoding for ``$text''
           Part or all of the message could not be encoded.  This may mean that the message
           contained characters not encodable in the CODE 128 character set, such as a character
           with an ASCII value higher than 127 (except the special control characters defined in
           this module).

       Unable to switch from ``$old_code'' to ``$new_code''
           This is a serious error in "start()" that indicates a serious problem occurred when
           switching between the codes (A, B, or C) of CODE 128.  If you get this error please
           contact the author.

       Unable to start with ``$new_code''
           This is a serious error in "start()" that indicates a serious problem occurred when
           starting encoding in one of the codes (A, B, or C) of CODE 128.  If you get this error
           please contact the author.

       Unknown code ``$new_code'' (should be A, B, or C)
           This is a serious error in "code()" that indicates an invalid argument was supplied.
           Only the codes (A, B, or C) of CODE 128 may be supplied here.  If you get this error
           please contact the author.

BUGS

       At least some Web browsers do not seem to handle PNG files with transparent backgrounds
       correctly.  As a result, the default for PNG is to generate barcodes without transparent
       backgrounds - the background is grey instead.

AUTHOR

       William R. Ward, wrw@bayview.com

SEE ALSO

       perl(1), GD