1Barcode::Code128(3)   User Contributed Perl Documentation  Barcode::Code128(3)
2
3
4

NAME

6       Barcode::Code128 - Generate CODE 128 bar codes
7

SYNOPSIS

9         use Barcode::Code128;
10
11         $code = new Barcode::Code128;
12

REQUIRES

14       Perl 5.004, Carp, Exporter, GD (optional)
15

EXPORTS

17       By default, nothing.  However there are a number of constants that
18       represent special characters used in the CODE 128 symbology that you
19       may wish to include.  For example if you are using the EAN-128 or
20       UCC-128 code, the string to encode begins with the FNC1 character.  To
21       encode the EAN-128 string "00 0 0012345 555555555 8", you would do the
22       following:
23
24         use Barcode::Code128 'FNC1';
25         $code = new Barcode::Code128;
26         $code->text(FNC1.'00000123455555555558');
27
28       To have this module export one or more of these characters, specify
29       them on the "use" statement or use the special token ':all' instead to
30       include all of them.  Examples:
31
32         use Barcode::Code128 qw(FNC1 FNC2 FNC3 FNC4 Shift);
33         use Barcode::Code128 qw(:all);
34
35       Here is the complete list of the exportable characters.  They are
36       assigned to high-order ASCII characters purely arbitrarily for the
37       purposes of this module; the values used do not reflect any part of the
38       CODE 128 standard.  Warning: Using the "CodeA", "CodeB", "CodeC",
39       "StartA", "StartB", "StartC", and "Stop" codes may cause your barcodes
40       to be invalid, and be rejected by scanners.  They are inserted
41       automatically as needed by this module.
42
43         CodeA      0xf4        CodeB      0xf5         CodeC      0xf6
44         FNC1       0xf7        FNC2       0xf8         FNC3       0xf9
45         FNC4       0xfa        Shift      0xfb         StartA     0xfc
46         StartB     0xfd        StartC     0xfe         Stop       0xff
47

DESCRIPTION

49       Barcode::Code128 generates bar codes using the CODE 128 symbology.  It
50       can generate images in PNG or GIF format using the GD package, or it
51       can generate a text string representing the barcode that you can render
52       using some other technology if desired.
53
54       The intended use of this module is to create a web page with a bar code
55       on it, which can then be printed out and faxed or mailed to someone who
56       will scan the bar code.  The application which spurred its creation was
57       an expense report tool, where the employee submitting the report would
58       print out the web page and staple the receipts to it, and the Accounts
59       Payable clerk would scan the bar code to indicate that the receipts
60       were received.
61
62       The default settings for this module produce a large image that can
63       safely be FAXed several times and still scanned easily.  If this
64       requirement is not important you can generate smaller image using
65       optional parameters, described below.
66
67       If you wish to generate images with this module you must also have the
68       GD module (written by Lincoln Stein, and available from CPAN)
69       installed.  Using the libgd library, GD can generate files in PNG
70       (Portable Network Graphics) or GIF (Graphic Interchange Format)
71       formats.
72
73       Starting with version 1.20, and ending with 2.0.28 (released July 21st,
74       2004), GD and the underlying libgd library could not generate GIF files
75       due to patent issues, but any modern version of libgd (since 2004) can
76       do GIF as the patent has expired.  Most browsers have no trouble with
77       PNG files.
78
79       In order to ensure you have a sufficiently modern installation of the
80       GD module to do both GIF and PNG formats, we require version 2.18 of GD
81       (which in turn requires libgd 2.0.28) or higher.
82
83       If the GD module is not present, you can still use the module, but you
84       will not be able to use its functions for generating images.  You can
85       use the barcode() method to get a string of "#" and " " (hash and
86       space) characters, and use your own image-generating routine with that
87       as input.
88
89       To use the the GD module, you will need to install it along with this
90       module.  You can obtain it from the CPAN (Comprehensive Perl Archive
91       Network) repository of your choice under the directory
92       "authors/id/LDS".  Visit http://www.cpan.org/ for more information
93       about CPAN.  The GD home page is:
94       http://stein.cshl.org/WWW/software/GD/GD.html
95

METHODS

97       new Usage:
98
99               $object = new Barcode::Code128
100
101           Creates a new barcode object.
102
103       option
104           Sets or retreives various options.  If called with only one
105           parameter, retrieves the value for that parameter.  If called with
106           more than one parameter, treats the parameters as name/value pairs
107           and sets those option values accordingly.  If called with no
108           parameters, returns a hash consisting of the values of all the
109           options (hash ref in scalar context).  When an option has not been
110           set, its default value is returned.
111
112           You can also set or retrieve any of these options by using it as a
113           method name.  For example, to set the value of the padding option,
114           you can use either of these:
115
116               $barcode->padding(10);
117               $barcode->option("padding", 10);
118
119           The valid options, and the default value and meaning of each, are:
120
121               width            undef    Width of the image (*)
122               height           undef    Height of the image (*)
123               border           2        Size of the black border around the barcode
124               scale            2        How many pixels for the smallest barcode stripe
125               font             "large"  Font (**) for the text at the bottom
126               show_text        1        True/False: display the text at the bottom?
127               font_margin      2        Pixels above, below, and to left of the text
128               font_align       "left"   Align the text ("left", "right", or "center")
129               transparent_text 1/0(***) True/False: use transparent background for text?
130               top_margin       0        No. of pixels above the barcode
131               bottom_margin    0        No. of pixels below the barcode (& text)
132               left_margin      0        No. of pixels to the left of the barcode
133               right_margin     0        No. of pixels to the right of the barcode
134               padding          20       Size of whitespace before & after barcode
135
136           * Width and height are the default values for the $x and $y
137           arguments to the png, gif, or gd_image method (q.v.)
138
139           ** Font may be one of the following: "giant", "large", "medium",
140           "small", or "tiny".  Or, it may be any valid GD font name, such as
141           "gdMediumFont".
142
143           *** The "transparent_text" option is "1" (true) by default for GIF
144           output, but "0" (false) for PNG.  This is because PNG transparency
145           is not supported well by many viewing software The background color
146           is grey (#CCCCCC) when not transparent.
147
148       gif
149       png
150       gd_image
151           Usage:
152
153               $object->png($text)
154               $object->png($text, $x, $y)
155               $object->png($text, { options... })
156
157               $object->gif($text)
158               $object->gif($text, $x, $y)
159               $object->gif($text, { options... })
160
161               $object->gd_image($text)
162               $object->gd_image($text, $x, $y)
163               $object->gd_image($text, { options... })
164
165           These methods generate an image using the GD module.  The
166           gd_image() method returns a GD object, which is useful if you want
167           to do additional processing to it using the GD object methods.  The
168           other two create actual images.  NOTE: GIF files require an old
169           version of GD, and so you probably are not able to create them -
170           see below.
171
172           The gif() and png() methods are wrappers around gd_image() that
173           create the GD object and then run the corresponding GD method to
174           create output that can be displayed or saved to a file.  Note that
175           only one of these two methods will work, depending on which version
176           of GD you have - see below.  The return value from gif() or png()
177           is a binary file, so if you are working on an operating system
178           (e.g. Microsoft Windows) that makes a distinction between text and
179           binary files be sure to call binmode(FILEHANDLE) before writing the
180           image to it, or the file may get corrupted.  Example:
181
182             open(PNG, ">code128.png") or die "Can't write code128.png: $!\n";
183             binmode(PNG);
184             print PNG $object->png("CODE 128");
185             close(PNG);
186
187           If you have GD version 1.20 or newer, the PNG file format is the
188           only allowed option.  Conversely if you have GD version prior to
189           1.20, then the GIF format is the only option.  Check the
190           $object->image_format() method to find out which you have (q.v.).
191
192           Note: All of the arguments to this function are optional.  If you
193           have previously specified $text to the "barcode()", "encode()", or
194           "text()" methods, you do not need to specify it again.  The $x and
195           $y variables specify the size of the barcode within the image in
196           pixels.  If size(s) are not specified, they will be set to the
197           minimum size, which is the length of the barcode plus 40 pixels
198           horizontally, and 15% of the length of the barcode vertically.  See
199           also the $object->width() and $object->height() methods for another
200           way of specifying this.
201
202           If instead of specifying $x and $y, you pass a reference to a hash
203           of name/value pairs, these will be used as the options, overriding
204           anything set using the $object->option() (or width/height) method
205           (q.v.).  However, this will not set the options so any future
206           barcodes using the same object will revert to the option list of
207           the object.  If you want to set the options permanently use the
208           option, width, and/or height methods instead.
209
210       barcode
211           Usage:
212
213               $object->barcode($text)
214
215           Computes the bar code for the specified text.  The result will be a
216           string of '#' and space characters representing the dark and light
217           bands of the bar code.  You can use this if you have an alternate
218           printing system besides using GD to create the images.
219
220           Note: The $text parameter is optional. If you have previously
221           specified $text to the "encode()" or "text()" methods, you do not
222           need to specify it again.
223
224   Housekeeping Functions
225       The rest of the methods defined here are only for internal use, or if
226       you really know what you are doing.  Some of them may be useful to
227       authors of classes that inherit from this one, or may be overridden by
228       subclasses.  If you just want to use this module to generate bar codes,
229       you can stop reading here.
230
231       encode
232           Usage:
233
234               $object->encode
235               $object->encode($text)
236               $object->encode($text, $preferred_code)
237
238           Do the encoding.  If $text is supplied, will automatically call the
239           text() method to set that as the text value first.  If
240           $preferred_code is supplied, will try that code first.  Otherwise,
241           the codes will be tried in the following manner:
242
243           1. If it is possible to use Code C for any of the text, use that
244           for as much of it as possible.
245
246           2. Check how many characters would be converted using codes A or B,
247           and use that code to convert them.  If the amount is equal, code A
248           is used.
249
250           3. Repeat steps 1 and 2 until the text string has been completely
251           encoded.
252
253       text
254           Usage:
255
256               $object->text($text)
257               $text = $object->text
258
259           Set or retrieve the text for this barcode.  This will be called
260           automatically by encode() or barcode() so typically this will not
261           be used directly by the user.
262
263       start
264           Usage:
265
266               $object->start($code)
267
268           If the code (see code()) is already defined, then adds the CodeA,
269           CodeB, or CodeC character as appropriate to the encoded message
270           inside the object.  Typically for internal use only.
271
272       stop
273           Usage:
274
275               $object->stop()
276
277           Computes the check character and appends it along with the Stop
278           character, to the encoded string.  Typically for internal use only.
279
280       code
281           Usage:
282
283               $object->code($code)
284               $code = $object->code
285
286           Set or retrieve the code for this barcode.  $code may be 'A', 'B',
287           or 'C'.  Typically for internal use only.  Not particularly
288           meaningful unless called during the middle of encoding.
289

CLASS VARIABLES

291       None.
292

DIAGNOSTICS

294       Unrecognized option ($opt) for $class
295           The specified option is not valid for the module.  $class should be
296           "Barcode::Code128" but if it has been inherited into another
297           module, that module will show instead.  $opt is the attempted
298           option.
299
300       The gd_image() method of Barcode::Code128 requires the GD module
301           To call the "gd_image()", "png()", or "gif()" methods, the GD
302           module must be present.  This module is used to create the actual
303           image.  Without it, you can only use the "barcode()" method.
304
305       Scale must be a positive integer
306           The scale factor for the "gd_image()", "png()", or "gif()" methods
307           must be a positive integer.
308
309       Border ($border) must be a positive integer or zero
310           The border option cannot be a fractional or negative number.
311
312       Invalid font $font
313           The specified font is not valid.  Note that this is tested using
314           GD->can(), and so any subroutine in GD.pm will pass this test - but
315           only the fonts will actually work.  See the GD module documentation
316           for more.
317
318       Image width $x is too small for bar code
319           You have specified an image width that does not allow enough space
320           for the bar code to be displayed.  The minimum allowable is the
321           size of the bar code itself plus 40 pixels.  If in doubt, just omit
322           the width value when calling "gd_image()", "png()", or "gif()" and
323           it will use the minimum.
324
325       Image height $y is too small for bar code
326           You have specified an image height that does not allow enough space
327           for the bar code to be displayed.  The minimum allowable is 15% of
328           the width of the bar code.  If in doubt, just omit the height value
329           when calling "gd_image()", "png()", or "gif()" and it will use the
330           minimum.
331
332       Unable to create $x x $y image
333           An error occurred when initializing a GD::Image object for the
334           specified size.  Perhaps $x and $y are too large for memory?
335
336       The gif() method of Barcode::Code128 requires the GD module
337       The gif() method of Barcode::Code128 requires version less than 1.20 of
338       GD
339       The png() method of Barcode::Code128 requires the GD module
340       The png() method of Barcode::Code128 requires at least version 1.20 of
341       GD
342           These errors indicate that the GD module, or the correct version of
343           the GD module for this method, was not present.  You need to
344           install GD version 1.20 or greater to create PNG files, or a
345           version of GD less than 1.20 to create GIF files.
346
347       No encoded text found
348           This message from "barcode()" typically means that there was no
349           text message supplied either during the current method call or in a
350           previous method call on the same object.  This error occurs when
351           you are trying to create a barcode by calling one of "gd_image()",
352           "png()", "gif()", or "barcode()" without having specified the text
353           to be encoded.
354
355       No text defined
356           This message from "encode()" typically means that there was no text
357           message supplied either during the current method call or in a
358           previous method call on the same object.
359
360       Invalid preferred code ``$preferred_code''
361           This error means "encode()" was called with the $preferred_code
362           optional parameter but it was not one of ``A'', ``B'', or ``C''.
363
364       Sanity Check Overflow
365           This is a serious error in "encode()" that indicates a serious
366           problem attempting to encode the requested message.  This means
367           that an infinite loop was generated.  If you get this error please
368           contact the author.
369
370       Unable to find encoding for ``$text''
371           Part or all of the message could not be encoded.  This may mean
372           that the message contained characters not encodable in the CODE 128
373           character set, such as a character with an ASCII value higher than
374           127 (except the special control characters defined in this module).
375
376       Unable to switch from ``$old_code'' to ``$new_code''
377           This is a serious error in "start()" that indicates a serious
378           problem occurred when switching between the codes (A, B, or C) of
379           CODE 128.  If you get this error please contact the author.
380
381       Unable to start with ``$new_code''
382           This is a serious error in "start()" that indicates a serious
383           problem occurred when starting encoding in one of the codes (A, B,
384           or C) of CODE 128.  If you get this error please contact the
385           author.
386
387       Unknown code ``$new_code'' (should be A, B, or C)
388           This is a serious error in "code()" that indicates an invalid
389           argument was supplied.  Only the codes (A, B, or C) of CODE 128 may
390           be supplied here.  If you get this error please contact the author.
391

BUGS

393       At least some Web browsers do not seem to handle PNG files with
394       transparent backgrounds correctly.  As a result, the default for PNG is
395       to generate barcodes without transparent backgrounds - the background
396       is grey instead.
397

AUTHOR

399       William R. Ward, wrw@bayview.com
400

SEE ALSO

402       perl(1), GD
403
404
405
406perl v5.32.0                      2020-07-28               Barcode::Code128(3)
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