dlsoft Barcode Analyser By dlsoft

Transcription

1 dlsoft Barcode Analyser By dlsoft

2 This manual was produced using ComponentOne Doc-To-Help.

3 Contents BarAnalyser 1 Introduction... 1 Barcode symbologies... 5 How to use BarAnalyser... 5 Walk through... 5 Scanning modes The Report Heading section Analysis section Scan results section Index 19 dlsoft Barcode Analyser Contents iii

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5 BarAnalyser Introduction dlsoft BarAnalyser is a tool for analysing high-resolution images of printed barcodes for the purpose of reporting on the quality and structure of the printed barcode. The images below illustrate just a few of the problems commonly encountered in creating barcodes: Incorrect check digit This image illustrates a GS1-13 barcode that appears to be structurally correct, but does not contain a valid GTIN (where the final digit is calculated from the preceding 12 digits). The final digit should be a 0. Missing bars This image shows a Code 39 symbol that has been truncated and the last few bars are missing. This can happen when a graphics image is pasted or loaded into a pre-defined space on a design with the pre-defined space being not quite large enough. dlsoft Barcode Analyser BarAnalyser 1

6 Over-generous printing ink This image shows a magnified section of a barcode that illustrates two of the most commonly encountered problems. Firstly the narrow bars (dark bars) are supposed to be the same width as the narrow spaces (light bars). Clearly they are not the bars are too thick and the spaces too thin. Secondly there is a considerable quantity of black ink spattered into the spaces, a problem often found with barcodes printed using ink-jet printers. Voids This image shows a magnified section of a barcode that illustrates another commonly encountered problem missing ink in sections of the bars, known as voids. While almost all barcodes printed on desktop printers will have voids these can become a problem when their number or size becomes comparable with the minimum bar width of the symbol being scanned. 2 BarAnalyser dlsoft Barcode Analyser

7 Contrast This image shows a section of a barcode that illustrates inadequate contrast between the bars (dark bars) and spaces (light bars). This problem can arise when a barcode image is printed onto coloured material, such as brown cardboard or craft paper. Resolution This image illustrates a problem commonly encountered when using thermal printers. The image was originally of good quality and designed for printing on a printer having a resolution of 300 dpi (dots per inch); however, after printing on a printer that had a resolution of 200 dpi the bars have become wider and the spaces have become smaller. Such distortions are unavoidable when images designed for one resolution are printed at a lower resolution. The reason is simple. The bars and spaces need to occupy a whole number of pixels. If an image designed for a dot size of 1/300 inches is printed on a printer that actually prints with a dot size of 1/200 inches then the printed dots will be larger than allowed for on the design. The increase in dark bar width over its nominal value is called the Bar Gain and is normally recorded as a percentage value. [A similar property is Bar Loss, which is when the Bar Gain is negative.] dlsoft Barcode Analyser BarAnalyser 3

8 The solution is of course to design the barcode image for the correct printer resolution. Modulation The image below shows bars exhibiting modulation Modulation may be cause by local variations in background reflectance (e.g., fragments of darker material in a recycled material), local variations in ink density of the bars, or show-through of contents on the reverse side of packaging material. It is also commonly encountered when graphic designers generate a PDF image of a design without ensuring that the PDF conversion process does not resample the image down to a low effective resolution. dlsoft BarAnalyser is designed to provide an approach to testing the quality of printed barcodes with the intention of avoiding some of these errors. What BarAnalyser is not BarAnalyser does not provide confirmation that a barcode is perfect or that it meets the standards laid down by various bodies. In particular you should bear in mind that: It does not measure bar height; so when a standard specifies a particular height or range of heights, you need to measure the height to ensure that you barcode complies. It cannot confirm the quality and accuracy of the data content of a symbol. It does not check that the Human Readable Interpretation matches the bar code data (and it may be necessary to check that the two correspond, particularly where the bar code generating software does not include Human Readable Interpretation data). Because only a portion of the symbol is actually scanned, the quality of all the entire symbol cannot be guaranteed beyond the statistical confidence limits associated with the sampling procedure used. Even a perfect symbol at the time of production can be damaged or otherwise affected in its passage through the supply chain (e.g., scratched, frozen, dampened, etc.). It cannot ensure that a barcode is the correct type for its intended purpose (e.g. an ITF-14 Symbol used on an item intended for retail Point-of-Sale). 4 BarAnalyser dlsoft Barcode Analyser

9 Barcode symbologies Barcode symbologies are not all the same. The decoding of barcodes is based on different aspects of the symbol in different symbologies. For example, GS1-13 and GS1-128 are edge-to-similar- edge decodable symbologies (ie. The distance from the front edge of a dark bar to the front edge of the next dark bar is an important measurement, rather than the width of the bar). Code 39 and Interleaved 2 of 5 barcodes on the other hand are two-width (narrow/wide) symbologies that cannot be decoded by the edge-to-similar-edge technique, but all element widths must be measured. They are, therefore, more subject to the problems caused by incorrect bar widths. Some barcode symbologies make use of a check digit or check character (one or two final characters determined by performing a mathematical operation on the preceding characters). For some symbologies this is mandatory, eg GS1-13 and GS1-128 both have mandatory check characters. In the case of GS1-13 the check character is the last character printed under the bars; however, the GS1-128 check character is not shown in human readable form (indeed it can be a non-printable character, such as a space or a newline). For such symbologies BarAnalyser will determine whether the check character in the decoded symbol is the correct character for the preceding characters. For some symbologies a check character is optional; eg. Code 39 and Interleaved 2 of 5 both allow optional check characters. For these barcode types BarAnalyser will report on whether the final character is a valid check character for the preceding characters, but will add that a check character is not mandatory in other words the designer may not have wanted the symbol to contain a check character, so the final character is simply that: the final data character. A similar warning will also be shown when reporting on ITF-14 barcodes which, although based on Interleaved 2 of 5, do not utilise the optional check digit. Reports on all Interleaved 2 of 5 symbols will also contain a statement to indicate whether the measured X dimension is within the allowed range for ITF-14. For GS1-128 symbols the presence of Function Code 1 (FNC1) in the first position after the start character is used as a flag for the GS1 System subset of the Code 128. BarAnalyser will test for this and for the other GS1-128 requirements: Use of FNC1 as a field separator following non-predefined length AIs Sequencing of AIs, with pre-defined length AIs preceding non pre-defined length ones Length of data fields with fixed length AIs Correct formatting of data in all AI fields Absence of encoded parentheses around AIs How to use BarAnalyser Walk through BarAnalyser is relatively simple to use. The following steps are required: Scan the barcode symbol with a quality flatbed scanner. Scanning should be at at least 1200 dpi although we recommend 2400 dpi or better; and in full colour (NOT Black and white or greyscale). The symbol should be scanned in its final configuration wherever possible (i.e, including any overlaminate, package material, contents). dlsoft Barcode Analyser BarAnalyser 5

10 Save the scanned image of the barcode area to a graphics file without using compression algorithms. So do NOT save as compressed JPEG files or compressed TIFF files as such formats will modify the edges of the bars in the symbol. BMP or PNG format are preferred. Open BarAnalyser. Drag the scanned image file onto the BarAnalyser window (or choose Open from the file menu and locate the scanned image file). 6 BarAnalyser dlsoft Barcode Analyser

11 Initially select Auto mode from the drop-down list of operating modes in the toolbar, then click the mouse on the barcode image, preferably close to the centre of the barcode. Note that the status bar at the bottom of the screen displays information about the success or failure of the processing of the image. If BarAnalyser can decode the symbol and the Report is enabled you can now view a summary of the report by selecting Summary from the View menu dlsoft Barcode Analyser BarAnalyser 7

12 Also you can view the full report and bar/space analysis by selecting View Report from the View menu or Print/preview report from the File menu. This will open a window containing a report of the analysis findings, permitting the report to be copied to the clipboard or printed. 8 BarAnalyser dlsoft Barcode Analyser

13 The top part of the report window displays any errors and warnings about the scanned symbol. This is followed by an analysis of the symbol, including the recorded contrast between dark and light bars, the size of the observed light margins, the value of the barcode X dimension and the corresponding Magnification (for GS1 symbols). Also shown are the mean dark bar and light bar element sizes and the corresponding Gain. Different barcode symbologies will result in different types of data being displayed in the report window. For example, GS1-128 symbols will also show where control characters (such as FNC1) were found in the symbol, and warn if variable length AIs occur before fixed length AIs. Scrolling down the report window reveals the detailed results for each bar in the symbol, its actual measured size, the nominal size it would be expected to have, and the deviation of the measured size from the nominal size as a percentage of the X dimension. A positive value of the deviation indicates that the bar is larger than expected (growth), while a negative value indicates that it is smaller than expected (shrinkage). The (RMS) mean values and the maximum values of the deviations for dark bars and light bars are also displayed. dlsoft Barcode Analyser BarAnalyser 9

14 If BarAnalyser cannot decode the symbol there are two ways to proceed: Ensure that the symbology name is checked in the symbology list on the left the BarAnalyser window. Now try again. [Note that some symbologies can be confused with others under some circumstances so it is not a good idea to enable all symbologies and hope for the best!] If the symbol cannot be decoded in Auto mode try using Laser mode or CCD mode (see below). If all else fails from the View menu select Barcode Creator and try to create a barcode of the same type and containing the same data. You should be able to see the difference between you scanned sample and the created symbol. The two windows may be compared with one above the other. Scanning modes Automatic mode In Automatic mode the user initiates analysis of a symbol by simply clicking the mouse while the cursor is pointing to an area inside the barcode symbol. 10 BarAnalyser dlsoft Barcode Analyser

15 BarAnalyser locates the elements of the symbol by checking both to the right and to the left of the mouse click. Laser mode While most symbols can be analysed using Automatic mode, some difficult images are more successfully handled using laser mode. To user Laser mode simply select Laser mode from the drop-down list of modes in the toolbar and then click the mouse to the left hand side of the symbol, as far to the left of the first bar as convenient while still inside the scanned image area. A red rectangle is drawn across the barcode highlighting the area of the image that will be processed. dlsoft Barcode Analyser BarAnalyser 11

16 CCD mode CCD mode is also useful for difficult images as it allows a larger section of the barcode symbol to be used for processing. To user CCD mode simply select CCD mode from the drop-down list of modes in the toolbar and then position the mouse to the left hand side of the symbol, as far to the left of the first bar as convenient while still inside the scanned image area, then hold down the left mouse button and drag the pointer down and to the right to draw a rectangle covering a portion of the symbol s height but its entire width including areas to the left and right of the symbol that contain no bars (the Light Margins). It is important to ensure that the drawn rectangle doe not contain any non-barcode material (such as adjacent text as in the image below). A red rectangle is drawn across the barcode highlighting the area of the image that will be processed. Releasing the mouse button cause the symbol to be analysed. 12 BarAnalyser dlsoft Barcode Analyser

17 The Report The report generated by BarAnalyser is divided into 3 sections: Heading, Analysis and Scan results. Heading section The Heading section records the following: date and time of the analysis, the resolution of the scanned image in pixels per inch, (e.g dpi) the type of symbol identified (e.g. GS1-8) the number of elements (bars and spaces) found in the symbol, excluding light margins (e.g. 75) the data decoded from the symbol, (e.g ) The Heading section them list any errors and /or warnings about the symbol. Errors can include messages to indicate that a symbol would not be useable for use with a standard barcode scanner, (e.g.a detected check character is incorrect for a barcode that has a mandatory check character). Any errors should be regarded as show stoppers! dlsoft Barcode Analyser BarAnalyser 13

18 Warning messages indicate that the symbol scanned has features that may render the symbol unsuitable for use (e.g. the light margins may be smaller that required, or the Gain may be too large). Any warnings should be investigated. In most cases additional details are included in the Analysis section of the report. Analysis section The Analysis section records the following: Contrast The detected contrast of the scanned image. This is recorded using the scanned Red level of the image by comparing the intensity returned from the bars and the spaces. This value should not be below 0.8. If a warning value (0.75) or an error value (0.5) is reported the scanned image should be examined in full screen mode to check for defects in the solid bars or ink spatter in the spaces. If the background colour is not white the barcode should be tested using the type of scanner for which the symbol is intended. Light Margins The observed left and right Light Margins. These are reported in units of X (the thickness of the symbols thinnest element) up to a maximum of 40X. Most 1D barcode types require light margins of 10X, although GS1 symbols have varying requirements. The values are also reported in millimetres and inches. If the detected light margin is smaller than that required for the barcode type a warning is also recorded in the Heading section. Note that when using Laser or CCD mode the left light margin may not be recorded correctly if the selected region does not include enough of the light margin. Bar height The observed bar height. If the resolution of the image is adequate, BarAnalyser will attempt to report on the height of the dark bars in units of X and millimetres and inches. If the resolution is not adequate this step is omitted. Check digit BarAnalyser tests whether the final character is the correct check character for the barcode type. If the barcode type has a mandatory check character than the test provides a simple response either the character is correct or it isn t (and if it isn t then the expected character is also recorded). If the barcode type has an optional check character the test returns whether the final character is suitable or not. BarAnalyser has no way of knowing whether the final character was simply that - the final character of the data or was intended to be the check character. Start and Stop bars BarAnalyser tests for the presence of the correct start and stop bars in the symbol. If the start bars are not found then the symbol is probably not decoded at all. If the stop bars are not found then the symbol may not scan with many barcode scanners. Stop bars are sometimes missing because a graphic artists has not allowed enough space for a barcode image placed onto artwork. Mean X dimension The mean value of the X dimension is calculated from all of the elements detected in the symbol and recorded in Mils (thousandths of an inch), along with the (RMS) error limits in this value. (Subsequent error limits are calculated from these.) Mean Wide/narrow ratio For those barcode types that have two allowed thickness for both bars and spaces (eg. Code 29, Interleaved 2 of 5), BarAnalyser records the mean value of the ratio of the Wide bars and spaces to the Narrow bars and spaces. Some uses require this value to be as close a possible to a specific value (e.g. 2.5), while other uses may allow the ratio to be between 2.0 and BarAnalyser dlsoft Barcode Analyser

19 Magnification Those barcode types that have a Nominal size, such as the GS1 barcodes, have the magnification detected for the symbol reported. This is calculated from the observed size compared with the nominal size, expressed as a percentage. Nominal height BarAnalyser records the height that the bars would be expected to have at the detected magnification for those barcode types that have a nominal height, such as the GS1 barcodes. The value is recorded in inches and millimetres and can be compared with the value obtained by measuring the original symbol. Mean bar element and mean space element These are the mean element sizes for the bars and spaces in the symbol reported in Mils. They will be the same if the Gain of the symbol is zero. Gain This is essentially a measure of how much thick the bar elements are than the space elements. The desirable value is 0. A Gain of more than 10% is usually a sign that the bars in the symbol are thicker than they should be while the spaces are smaller. This may be cause by printing at too low a resolution for the size of symbol, or because the ink has spread outward from the bars. Mean and maximum deviations The mean and maximum deviation of the observed dark bar and light bar thickness from the corresponding nominal size is reported as a percentage. No mean value should be larger than 5% and no maximum value should be larger than 10%. Scan results section The scan results section records the observed widths of the dark and light bars in the symbol, with the bars numbered from the first (lefthand) dark bar. There are two classes of barcode and the reports are different for the two classes. The first class contains two bar thicknesses (wide and narrow), and detection relies on determining the sequence of the wide and narrow bars and spaces. For these barcode types the report records for each element whether it should be a dark bar (B) or space (S) and whether it should be a Wide element (W) or Narrow (N). It also records the actual number of pixels observed for the element and the percentage deviation from the expected value (as shown below). dlsoft Barcode Analyser BarAnalyser 15

20 The second class of symbols allows more than two bar and space widths, with each allowed width being an integer multiple of the thinnest element. For these symbols BarAnalyser records for each element whether it should be a dark bar (B) or space (S), and nominal thickness the element should have at the detected resolution, and the actual observed thickness, along with the percentage deviation from the nominal value (as shown below). 16 BarAnalyser dlsoft Barcode Analyser

21 When a symbol has a supplementary barcode, such as the sample below, the report identifies the space between the main and supplementary symbol and specifies the range allowed by the barcode specification. dlsoft Barcode Analyser BarAnalyser 17

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23 Missing bars 1 Modulation 4 Index A Analysis section 14 Automatic mode 10 B Bar height 14 Barcode symbologies 5 C CCD mode 12 Check digit 14 Contrast 3, 14 G Gain 15 N Nominal height 15 O Over-generous printing ink 2 R Resolution 3 S Scan results section 15 Scanning modes 10 Start and Stop bars 14 T The Report 13 V Voids 2 W Walk through 5 H Heading section 13 How to use BarAnalyser 5 I Incorrect check digit 1 Introduction 1 L Laser mode 11 Light Margins 14 M Magnification 15 Mean and maximum deviations 15 Mean bar element and mean space element 15 Mean Wide/narrow ratio 14 Mean X dimension 14 dlsoft Barcode Analyser Index 19