Barcode Reference Guide

Transcription

1 Version 1.0 Barcode Reference Guide Revision 3 3/24/2003

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3 Barcode Module Reference Guide Barcode Reference Guide Revision 3 3/24/2003

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5 Table of Contents Introduction...7 Barcode...7 Requirements...7 Barcode Sources...7 Barcode Symbol Types...8 Installation...9 Licensing...9 Installation...9 Barcode Recognition...10 Reliability...10 Basic facts...10 What Barcode to choose where to find it...11 Resolution (DPI)...11 Recommended symbol width...11 Vertical symbol size...12 Barcode symbol skew...12 Quiet zones...12 Scanner adjustment...12 Document quality...13 Label quality...13 Barcode Settings...14 Template Setup...14 Barcode Options...15 Barcode Regions...15 Recognize Types...16 Recognition Options...16 Sample Barcodes...19 Barcode Module Reference Guide

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7 Introduction Barcode The DocSTAR Barcode module provides a high performance software engine for barcode recognition from scanned documents. It provides fast and reliable barcode recognition technology that works without any additional hardware support and without slowing down the scanner. Once barcode symbols are read, the information can be used during the filing process to index documents. Requirements The DocSTAR Barcode module requires DocSTAR version 3.1 Build 25 or higher to be installed on the DocSTAR host and client stations. A barcode license must be installed on the host for each user who will be running templates with barcode zones. Barcode Sources Of course, one additional requirement is the presence of barcodes on your documents. It is possible that you are already receiving documents containing barcodes from a vendor, client, or other source. In this case, you don t have to figure out how to create the barcodes, but you don t have any control over the quality of the barcodes you are receiving. If you are unable to achieve reliable recognition using the settings recommended herein on such barcodes, you will have to work with the barcode source to generate larger or clearer barcodes on your documents. On the other hand, your application may lead you to create barcodes on documents. A number of thirdparty solutions are available to print barcodes on documents or on labels. Part of this Reference Guide is devoted to helping ensure that barcodes you create are of satisfactory size and quality to ensure reliable recognition. Barcode Module Reference Guide 7

8 Barcode Symbol Types The DocSTAR Barcode module can recognize most common barcode types. The table below lists the recognized types and the specifications for each barcode type including the character set supported, maximum string length and check character options. Type Barcode Numerical Characters Alpha Characters Special Characters String Length Check Character EAN N/A N/A 13 Optional EAN N/A N/A 8 Optional UPCA 0-9 N/A N/A 12 Always UPCE 0-9 N/A N/A 6 Always Code A-Z, Space -. $ % + / No limit Optional Code 128 All ASCII characters No limit Always Interleave 2 of N/A N/A No limit (even) Optional Codabar 0-9 a,b,c,d (must be first or last) -. $ % + / No limit Optional Barcode Module Reference Guide 8

9 Installation Licensing The DocSTAR Barcode engine requires a license certificate for each user filing station that will be running filing using the barcode recognition engine. This is different from view and view/file licenses that can be used by multiple users and only restrict concurrent use. The DocSTAR Barcode module requires a separate paid license for each station that runs the barcode engine. The first time a template with barcodes is run on a user station, a barcode license is used on that station. When the number of barcode licenses installed on the system are used up, no more stations will be allowed to run barcode templates. All users can view and edit a template with barcode zones (with or without a license) but only those with a barcode license can run a template with barcodes. If a station without a barcode license attempts to run a template with a barcode zone, a message will be presented telling them they do not have a license and allowing them to continue without using the barcode engine. Installation The DocSTAR barcode license certificates are installed into the license system through the Administration program. Each certificate licenses a specific number of users and multiple certificates can be added to one hardware key. Contact DocSTAR technical support for the proper authorization number to add certificates. Barcode Module Reference Guide 9

10 Barcode Recognition Reliability Document scanners are raster-oriented devices, which capture images from paper documents and typically operate at 200 to 400 DPI (Dots Per Inch). Valuable information gets lost when capturing a non-rastered symbol, such as a barcode, with a rastered device like a document scanner. There are many more factors that lead to additional loss or even distortion of information. Disappointing recognition results can only be avoided by controlling all factors as closely as possible. The following list helps the user to identify, understand and control the issues that directly influence the reliability of barcode recognition. The issues listed below are not ranked in any particular order: Barcode type and quality Resolution (DPI) Symbol width Vertical symbol size Skew of the barcode symbol Quiet zones Scanner settings Document quality Label quality Basic facts Barcode recognition is mainly used for indexing purposes where significant automation may be accomplished. System performance and data integrity depend on the accuracy and reliability of the barcode recognition engine and the image quality. The DocSTAR barcode engine incorporates the best possible read algorithms but that does not in itself automatically ensure good results. The most deceiving thing about barcode symbols is that, what may look like a fine barcode symbol to the naked eye, is in reality a collection of zebra like stripes that contain no valuable information at all. Information is embedded in barcode symbols in the width of white bars and black bars as well as in the position and association of white bars and black bars to each other. Anything that distorts or erodes white or black bars makes a barcode symbol susceptible to read errors and in extreme situations a symbol may become totally unrecognizable. Simply stated... Information that is not there cannot be read! In order to obtain reliable barcode recognition, it is necessary for the user to understand and to properly control all of these factors. Barcode Module Reference Guide 10

11 What Barcode to choose where to find it The structure and internal architecture of a barcode symbol causes it to be more or less susceptible to a reduction in recognition reliability. Barcode type Code 39 appears to show the highest tolerance for a marginal degradation of input data. For that reason, DocSTAR recommends the use of Code 39 over other symbologies. Code 39 and other barcodes can be created from various software products. Some of these are font-based, which makes them convenient to use, but the accuracy of the symbols in barcode fonts varies greatly. Be cautious selecting a barcode source. Check references and/or perform a series of tests to ensure reliable recognition for your application. Resolution (DPI) Barcode symbols may be reliably read from 200, 300 and 400 DPI images, but lower DPI settings require larger barcode symbols for adequate recognition. In order to obtain reasonable results, it is recommended that the character density for barcode symbols be kept at or below the suggested values listed in the following paragraph. Recommended symbol width The width of a barcode symbol is a very important (if not the single most important) factor directly relating to the reliability of barcode recognition. The wider the barcode symbol, the better the symbol definition, and consequently recognition! The task is to get the barcode recognition rate as close to the 100% mark as possible. There is no fixed formula to determine the best possible width. The general rule of thumb is that there should not be more than: 8 characters per running inch in 400 DPI mode 6 characters per running inch in 300 DPI mode 4 characters per running inch in 200 DPI mode 2 characters per running inch in 100 DPI mode These numbers include all the characters in the symbol such as the synchronization character, the data characters, the stop character and the optional check character. Example: Given a 300DPI image and a 12-character data string with check character enabled, the symbol ends up containing a total of 15 characters. Using 300DPI the minimum symbol width may be calculated as follows: Symbol width equals: 15 Characters divided by 6 per inch = 2.5 inches Barcode Module Reference Guide 11

12 Vertical symbol size The DocSTAR Barcode engine is theoretically capable of recognizing a barcode symbol that is only one scan line high. An issue often arises due to barcode symbols frequently having various degrees of skew. This skew is introduced when manually attaching barcode labels, through printer misalignment or because of scanner misalignment. Normally the DocSTAR Barcode engine reads barcode symbols from the left to the right. The best reliability is obtained when the barcode is aligned adequately for a single horizontal scan line to traverse the entire symbol starting with the sync-character and ending with the end-character. To keep the left and the right edge of a symbol within a single horizontal scan line, the symbol must be made vertically tall enough to allow for the maximum skew angle. Additional height must be provided to allow for frequently observed bleeding and partial dilation, which can occur at the top and bottom of barcode symbols. Barcode symbol skew The DocSTAR Barcode engine has a skew enable feature that allows the reading of barcode symbols that are not tall enough or are skewed beyond the point where a single scan line traverses the entire symbol. This is a valuable tool for recovering badly skewed symbols. However, this feature introduces a slight reduction in recognition speed and may possibly open the way for read errors caused by data that is less than perfect. Systems should only use this feature as a backup, and not for normal operations. Quiet zones Most barcode standards define a quiet zone to the left and the right of a barcode symbol. In a bitmap this quiet zone should be all white. The absence of a quiet zone is typically caused by noise, underlying text or edges of labels. This may prevent the DocSTAR Barcode engine from detecting sync-characters. In that situation the engine may return a status with: Barcode not found. It is also necessary for all barcode symbols to have additional quite zones at the top and at the bottom. A quiet zone at the top or bottom of a barcode symbol must be over three pixels high. The quiet zones at the left and right side of the barcode symbol must be over eight pixels wide. Scanner adjustment Many scanners have an option that allows the Contrast to be adjusted. This threshold setting basically defines at what level of gray a pixel is interpreted as being black or white. The idea of this control is to adjust the scanner to better match the actual properties of individual documents. An unpleasant byproduct of this control is that it causes the black bars in barcode symbols to appear wider or narrower than they actually are. This process is also referred to as dilation. In other words, the width ratio of black bars to white bars become distorted and barcode symbols end up being unrecognizable even though they appear to the human eye as being fully acceptable. It is necessary to carefully adjust this control so that the ratio of black bar width to white bar width in the bitmap is identical to the ratio shown on the original document. Barcode Module Reference Guide 12

13 Document quality It can be very difficult to determine if a barcode symbol has adequate detail for reliable recognition. The simplest way to decide is to scrutinize barcode symbols for proper contrast and sharp edges the same way as looking at the text portion of a document to determine it s image quality. Label quality One technique used to place barcode symbols onto documents is to affix adhesive labels. Using this procedure raises a number of concerns: Are the labels large enough for the edges to not violate the requirement for quiet zones? Are the symbols of good resolution? Print resolution should be 300DPI or better. Labels printed on matrix printers are not acceptable. Label printers using cloth ribbon are also a major source of headache. Is the adhesive quality adequate to prevent curling or the labels coming loose? Barcode Module Reference Guide 13

14 Barcode Settings Template Setup Once a barcode license is installed into the system, a new data source called Barcode engine appears in the zone drop down list. After selecting a barcode engine zone you can define a region to be searched for barcodes. If you do not define a region the entire page will be searched for barcodes. Each barcode zone can have options set which control how barcodes are recognized from the region. Barcode Module Reference Guide 14

15 Barcode Options Clicking the Set Options button will show the options screen below: Barcode Regions A region of interest can be defined for each barcode zone. When defining a region for a specific barcode, draw the region larger than the barcode appears on screen. The region should include ample white space outside the bound of the barcode image such that, even though barcode placement (registration) may vary somewhat, there will still be a quiet zone around the barcode. Barcode Module Reference Guide 15

16 Recognize Types The DocSTAR barcode engine can read eight different types of barcodes, which comprise the most common types of barcodes used. We recommended selecting only the barcode type you know to be present to speed recognition. However multiple barcode types can be selected in situations when you don t know which barcode type will be present. Recognition Options Read directions The engine supports all four basic reading directions, Left to right, Right to left, Top down, and Bottom up. Each can be turned on independently to allow recognition of barcodes in any orientation. Read granularity Granularity controls the number of scan lines skipped when detecting barcodes. The default setting for this value is nine (9). Most of the time the engine is capable of locating a barcode symbol based on this default setting. The lower the number, the slower the barcode recognition is. Read white space Granularity controls the number of scan lines used to locate the bounding rectangle of a barcode. The default setting for this value is five (5). Most of the time the engine is capable of locating a barcode symbol based on this default setting. This number should be increased if the barcode has unusually jagged edges. Minimum acceptable barcode length The minimum acceptable barcode length should always be set equal to the number of characters contained in the symbol that is to be read. The DocSTAR barcode engine will not report back any string that is shorter. The reason for having this parameter is to prevent erroneous returns based on barcode like pattern found in text. Settings of four (4) and larger prevent most of these false returns. When the targeted barcode string does not contain a check character this value should equal the number of characters in the string. When the string contains a check character this value should be set to the number of characters in the string plus one (1). Maximum number of barcodes per zone The engine will return multiple barcodes found per zone up to the number found in this setting. If you want to return only one barcode per zone set this number to 1. Allow partial barcodes The engine can return even partial barcodes is this option is used. Generally this is not recommended because the data may not be valid. Enable error checking Only apply error checking if the barcode you are reading includes a check character. When the engine finds a barcode and the check character does not match, it automatically keeps reading scan line after scan line until the first string was read with a matching check character. If the process fails no barcode will be returned if error checking is enabled. Barcode Module Reference Guide 16

17 Reading with check character disabled The engine reads many scan lines inside a barcode symbol. Each scan-line may produce a string. If a check character is not used, the string is only checked for the presence of a sync character and end character. It must also match the Minimum length parameter. Because of the missing check character test the engine may read many different strings depending on symbol size and quality. The string that has been read most often is returned to the caller. It is important for the user to understand that the engine has no way of knowing if this information is correct or not. For a reliable production environment it is recommended that users work only with barcode symbols that contain a check character. Mixed mode reading It is not recommended to have check-character enable set and to read barcode symbols that do not contain a check-character. This will cause the engine to slow down significantly. Barcode Module Reference Guide 17

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19 Sample Barcodes Code 39 Interleaved 2 of 5 Code 128 Codabar EAN 13 UPC-A EAN 8 UPC-E Barcode Module Reference Guide 19