PDF417 Barcode FAQ & Tutorial
The PDF417 barcode is a two-dimensional (2D), high-density symbology
capable of encoding text, numbers, files and actual data bytes. This
FAQ provides information and answers to commonly asked questions.
PDF417 Barcode Overview
Large amounts of text and data can be stored securely and inexpensively
when using the PDF417 barcode symbology. The printed symbol consists
of several linear rows of stacked codewords. Each codeword represents
1 of 929 possible values from one of three different clusters. A different
cluster is chosen for each row, repeating after every three rows. Because
the codewords in each cluster are unique, the scanner is able to determine
what line each cluster is from.
PDF417 Error Correction Levels
PDF417 uses Reed Solomon error correction instead of check digits.
This error correction allows the symbol to endure some damage without
causing loss of data. AIM standards recommend a minimum error correction
level of 2. The error correction level depends on the amount of data
that needs to be encoded, the size and the amount of symbol damage that
could occur. The error correction levels range from 0 to 8. The chart
below indicates the number of error correction codewords that are added
to the printed symbol and AIM recommendations for the EC level.
Fig. 1: AIM recommended EC levels
|EC Codewords Generated
|Data Bytes Encoded
X and Y Dimensions
- The X dimension is the width of the narrowest bar in a printed codeword.
The Y dimension is the height of each row within the PDF417 symbol.
The PDF417 barcode is usually printed at an X to Y ratio of 1:2 to 1:5,
with 1:3 being the most popular. By lowering the ratio, a significant
amount of space can be saved; however, some scanners cannot read X to
Y ratios of less than 1:3. Most scanners, such as the
IDAutomation PDF417 2D USB Scanner, read PDF417 barcodes well at 1:3.
When creating symbols with more than 10 columns, IDAutomation recommends
using a ratio of 1:4 or 1:5.
Row and Column Limits
- The number of rows and columns can be selected, allowing the symbol
to be created in various forms. However, the PDF417 barcode symbol is
limited to 30 columns and 90 rows. Keep in mind when selecting columns,
only the number of data columns in the symbol are being selected. The
normal PDF417 barcode symbol has two row start columns and two row stop
columns. Truncated PDF417 contains only two row start columns. Some
scanners and decoders cannot dependably read over 20 columns.
- A truncated PDF417 symbol uses less area than the normal PDF417 barcode.
By selecting this option, the right hand side of the symbol is removed
or truncated. This option should be used primarily in a clean environment,
since it is more susceptible to damage.
Generating and Printing
PDF417 Barcode Font and Encoder is a
collection of encoders and components that generate PDF417 symbols
as graphics or as a font. All of our PDF417 products were created from ISO/IEC
15438. IDAutomation also offers new patent-pending
Native Barcode Generators for
and Microsoft Access
that create PDF417 without any plug-ins or fonts.
Integration Guides are also available that offer one or more integration
options. These options may be examined to determine the best implementation
method. A few of the guides offered include the following:
Measuring X & Y Dimensions of a Printed Barcode
Barcode products generate images according to the pixels of the target
device thereby creating an image difference. Consequently, it may be
necessary to check the X or Y dimensions. Images and symbol sizes may
differ slightly with various screen resolutions and printers.
To find the printed Y dimension
- Print a PDF417 barcode symbol
with exactly 10 rows.
- To obtain 10 rows, choose 5 columns, an error
correction of 2 and print the text of "IDAutomation.com, Inc. PDF417
ActiveX Control" with binary encoding.
- Measure the distance from the
top of the symbol to the bottom and divide by 10.
- Example: if 10 rows
measured .425 inches, then .425" divided by 10 equals .0425", giving
a Y dimension of 42 mils per row.
To find the printed X dimension
- Measure 6 or more columns, but
do not include the start and stop columns in the measurement, divide
this number by the number of columns measured, then by 17. The result
is the X dimension.
- Example: if 6 columns measure .875", divide .875”
by 6, which equals .14583" per column. Because the X dimension width
of each column is 17, take the .14583" and divide it by 17, which equals
.00857", which is about 8 mils.
Compaction Modes & Amount of Data Encoded
It is recommended to limit the amount of data in each 2D barcode
symbol to 800 characters or less, using 20 columns or less. Although
the specification states that "up to 1100 bytes or 1800 ASCII characters
can be encoded in a PDF417 symbol," it is not usually achievable. The
amount of data that can be encoded will vary depending upon the type of data,
the compaction type, the error correction level chosen and the limitation of the
scanner being used. For example, in text compaction mode, the amount of
compaction varies due to mode switching between different types of characters,
such as between numbers, upper case, lower case and punctuation. In addition,
many PDF417 CCD
scanners do not reliably read more than 800 to 850 characters and some
scanners have limits of only 300 characters.
If it is necessary to encode more than 800 characters,
IDAutomation recommends using Macro PDF mode
or multiple separate symbols. In the best-case scenario, using the
text encoding mode of the IDAutomation
PDF417 Forms Control
2D Barcode Scanner, up to 1200 characters were successfully encoded
Each codeword represents 1 of 929 possible values, which allows data
to be compacted into the codewords to save space. PDF417 has three data
compaction modes: byte, text and numeric. Binary compaction encodes
actual bytes of data; text mode encodes most characters on the U.S.
keyboard. Numeric compaction encodes only numbers, is rarely used and
not available in all products due to calculation limitations. The chart
below shows more details about these modes.
0 to 255
||1.2 bytes per codeword
9,10,13 & 32-127
||2 characters per codeword
||only numbers 0-9
||2.9 digits per codeword
To encode the most amount of data into the smallest
The amount of data compaction will vary depending upon the type of
data that is being encoded and the error correction level chosen. If
the scanner supports it, smaller symbols may be obtained by performing
any of the following:
- Use TEXT compaction mode.
- Decrease the error correction level to 2.
- Increase the number of columns to the largest possible size.
- Decrease the X dimension to the smallest possible size the scanner
- Turn on truncation, which decreases the symbol size by two columns.
- Choose an X to Y ratio of 1:3.
Encoding Functions (such as Tabs
to be easily encoded for various operations such as encoding tabs and
returns. Normally, these characters are not visible unless an application
is used such as IDAutomation's
ASCII String Decoder, which displays these hidden functions as tags.
In all IDAutomation products, the tilde (~) may be used to encode
For example; ~009 is used to encode a tab
and ~013 encodes a return. In many development
environments, Chr or Char may also be used to encode the ASCII value
directly. For example, the programming examples below encode "PDF" <tab>
Java: DataToEncode= "PDF" + (char)9
Visual Basic: DataToEncode= "PDF" & Chr(9)
Encoding Data for FedEx® applications:
FedEx uses a combination of Code 128 and PDF417 barcodes on packing
slips to automate delivery and tracking. FedEx publishes a
FedEx Ground Multicode Barcode Label
Guide and a
Barcode and Label Layout Specification Guide that should always
be examined when implementing FedEx label applications.
The following is a summary of the PDF417 barcode requirements for
FEDEX label printing:
- The PDF Security Level or Error Correction Level must be set
- The X dimension must be 10mils (.010" or .0254 CM) with an X
to Y ratio (or N Dimension) of 5. To achieve this with the
and Encoder, print with the IDAutomationPDF417n5 font
at 11 points.
- The number of columns should be set to 10.
- The entire message should not exceed 350 characters.
- The quality of the symbol must be ANSI grade "A". The
2D Barcode Scanner's Print Quality Assessment may be
used as a guide for this requirement.
- The data encoded must begin with: [)>RS01GS
where RS is
30 and GS is ASCII 29. In IDAutomation products, if
ApplyTilde if set to "True" or "1,"
the format ~ddd is used to specify the ASCII code of the
character to be encoded. These characters cannot be viewed or printed
and therefore it may not appear to be present, unless an application
is used such as IDAutomation's
ASCII String Decoder.
NOTE: The code supplied below is an example and not a complete solution.
More information about structuring messages to meet FedEx label specifications
may be found at the
char GS = (char)29;
char RS = (char)30;
char EOT = (char)4;
rm.setData("[)>"+RS+ "01"+GS+ "9633626"+GS+ "840"+GS+
Visual Basic Example:
Dim NewMessage As String
Dim GS As String
Dim RS As String
Dim EOT As String
GS = Chr(29)
RS = Chr(30)
EOT = Chr(4)
NewMessage = "[)>" + RS + "01" + GS + "9633626" + GS + "840" + GS +
"002" + GS + "12345678901" + GS + "RPSC" + GS + "0988443"...
PDF4171.DataToEncode = NewMessage
Tilde Processing of Control Characters
IDAutomation PDF417 barcode products all support the format ~ddd
to specify the
of the character to be encoded, which allows easy encoding of GS, RS
and EOT from the command line.
For example, the following string:
"[)>"+RS+ "01"+GS+ "0133626"+GS+ "840"+GS+
May also be encoded with this string:
Before implementing the printed PDF417 barcodes for FedEx applications,
it is recommended to verify the symbol with the Print Quality Assessment
test of the
2D Barcode Scanner or another suitable
verifier. Additionally, the
Focus Scanner together with the
Scanner ASCII String Decoder may be used to view the non-printable
RS, GS and EOT lower
which will appear as tags. To perform the test, simply open the Barcode
Scanner ASCII String Decoder and scan a MaxiCode symbol with the Image
Encoding International & Extended Characters
It is possible to scan and encode international and extended characters,
provided the instructions below are followed:
- Encode the data using binary encoding. This option
encodes all data, byte-by-byte.
- Scan the data via the serial interface option (data bits
have to be 8N) on the scanner. Normally, keyboard wedges and USB
scanners do not support extended characters above ASCII 128, and
only scan characters that are actually on the keyboard. Contact
the scanner vendor for more information; some of the scanner's internal
settings may have to be modified.
Reading PDF417 Barcodes
The most common
method of reading barcodes is with a
Capable Barcode Scanner such as the
2D Barcode Scanner with PQA, which reliably reads the IDAutomation
when printed as small as 3 points, which is an X-dimension of only 5
mils. Most of the hand-held barcode imagers recommended by IDAutomation
perform keyboard emulation and receive power from the USB port, so that
no external power supply is needed. When a barcode symbol is read using
keyboard emulation, the data appears at the cursor as if it had been
typed in from the keyboard.
In some cases, it may be desired to have the scanner trigger a form
or action in an application. IDAutomation has documented easy methods
of accomplishing this in the
USB Barcode Scanner
Application Integration Guide.
Verifying PDF417 Barcodes
symbols may be easily verified with the Print Quality Assessment test
found in the
2D Barcode Scanner. The quality assurance test will grade the symbol
and report the X dimension, Y dimension and any possible problems. The
report below was generated when scanning the PDF symbol to the right
with PQA enabled:
>> PQA <<
PDF417: 10 rows x 3 cols, 22 data & 8 chks (ECL = 2)
X roughly = 0.009"
[A] < Row Height = 3.1 X
[A] < Useful Row Height = 2.4 X (76% Row)
[A] < Data Safety Margin = 100% (0 Erasures & 0 Errors)
[A] < Edge Accuracy = 72%
[A] < Print Growth = +1% of X
MacroPDF417 is an implementation of PDF417 capable of encoding very
large amounts of data into multiple PDF417 barcodes. These multiple
barcodes are then scanned by a MacroPDF enabled scanner, which reassembles
them into one string of data. Each MacroPDF barcode segment shares a
file ID with the other segments, which make up the entire barcode sequence.
If the file ID is not the same, the scanner will assume that each of
the segments belong to a different barcode sequence. In order for the
scanner to reassemble the barcode in the correct order, each segment
of the barcode must have a unique segment index, starting at zero. This
unique segment index allows the scanner to know how to reassemble the
barcode segments, and allows reading symbols in non-sequential order.
2D products that generate MacroPDF417 symbols:
Scanner that reads and assembles MacroPDF symbols:
Macro PDF417 Example
MacroPDFEnable = True
MacroPDFFileID = 237
MacroPDFSegmentIndex* = 0
MacroPDFLastSegment = False
MacroPDFEnable = True
MacroPDFFileID = 237
MacroPDFSegmentIndex* = 1
MacroPDFLastSegment = True
Macro PDF417 Properties
- Macro PDF Enable - A boolean indicating that this barcode
is part of a
- Macro PDF File ID - Assigns a file ID to the MacroPDF
barcode. Each barcode in the MacroPDF sequence must have the same
file ID assigned to it. Default is 0; valid options are 0-899.
- Macro PDF Segment Index - The index number of this MacroPDF
barcode in relation to the set. Default is 0; valid options are
0-99998; * each barcode in the MacroPDF sequence must have a unique
segment index, starting at zero and incrementing thereafter by 1.
- Macro PDF Last Segment - A boolean indicating that this
is the final barcode in the MacroPDF sequence.
If assistance is needed, please
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