Barcode::Code128(3) User Contributed Perl Documentation Barcode::Code128(3)NAMEBarcode::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
DESCRIPTIONBarcode::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.pm module (written by Lincoln Stein, and available from CPAN)
installed. Version 1.20 or higher of GD generates a PNG file, due to
issues with the GIF patent. If you want to create a GIF, you must use
version 1.19 or earlier of GD. However, most browsers have no trouble
with PNG files.
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) # for old versions of GD only
$object->gif($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 ALSOperl(1), GD
perl v5.14.1 2007-07-17 Barcode::Code128(3)