Barcode::Code128 - Generate CODE 128 bar codes
use Barcode::Code128;
$code = new Barcode::Code128;
Perl 5.004, Carp, Exporter, GD (optional)
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
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
- 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.
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. $code may be 'A', 'B',
or 'C'. Typically for internal use only. Not particularly meaningful
unless called during the middle of encoding.
None.
- Unrecognized option ($opt) for $classUnrecognized option ($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. $opt is the attempted option.
- The
gd_image() method of Barcode::Code128 requires the GD moduleThe gd_image() method of Barcode::Code128 requires the GD module
-
To call the
gd_image(), png(), or gif() methods, the GD
module must be present. This module is used to create the actual
image. Without it, you can only use the barcode() method.
- Scale must be a positive integer
-
The scale factor for the
gd_image(), png(), or gif() methods
must be a positive integer.
- Border ($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 $y are too large for memory?
- The
gif() method of Barcode::Code128 requires the GD moduleThe gif() method of Barcode::Code128 requires the GD module
-
- The
gif() method of Barcode::Code128 requires version less than 1.20 of GDThe gif() method of Barcode::Code128 requires version less than 1.20 of GD
-
- The
png() method of Barcode::Code128 requires the GD moduleThe png() method of Barcode::Code128 requires the GD module
-
- The
png() method of Barcode::Code128 requires at least version 1.20 of GDThe png() method of Barcode::Code128 requires at least version 1.20 of GD
-
These errors indicate that the GD module, or the correct version of
the GD module for this method, was not present. You need to install
GD version 1.20 or greater to create PNG files, or a version of GD
less than 1.20 to create GIF files.
- No encoded text found
-
This message from
barcode() typically means that there was no text
message supplied either during the current method call or in a
previous method call on the same object. This error occurs when you
are trying to create a barcode by calling one of gd_image(),
png(), gif(), or barcode() without having specified the text
to be encoded.
- No text defined
-
This message from
encode() typically means that there was no text
message supplied either during the current method call or in a
previous method call on the same object.
- Invalid preferred code ``$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.
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.
William R. Ward, wrw@bayview.com
perl(1), GD
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