Click here to Skip to main content
14,241,807 members

Reading Barcodes from an Image - III

Rate this:
4.87 (119 votes)
Please Sign up or sign in to vote.
4.87 (119 votes)
19 Oct 2009CPOL
Detects Code39, EAN, and Code128 barcodes in an image.

Screenshot

Acknowledgement

This project is based on the CodeProject article: Reading Barcodes from an Image - II by qlipoth. I asked and got permission from qlipoth to publish an enhanced version of his code.

Introduction

My company has a need for reading barcodes from images that also contain text on the same page as the barcode(s). When searching for a solution in C#, I found qlipoth's CodeProject article: Reading Barcodes from an Image - II. His code came a long way towards what I wanted, but I needed a few improvements. In the end, my changes amounted to a significant rewrite that justifies a new CodeProject publication.

Background

This code has several improvements compared to the original code written in 2005:

  1. Validation is added for Code39 barcodes. The code has much less chance of detecting a "barcode" that is not actually present.
  2. Detection speed is improved. The main problem in the original project was that it used Bitmap.RotateFlip, and that function is quite slow.
  3. Added EAN/UPC and Code128 barcode support. The original project could only detect Code39 barcodes.
  4. Fixed some bugs that were reported for qlipoth's project and for the related project Reading Barcodes from an Image published by Benjamin Liedblad in 2004.

Using the code

To open the solution, you'll need Visual Studio 2008. However, I have not used any constructs that are not .NET 1.1 compatible, so the actual code should also be compilable in Visual Studio 2003 or 2005.

To use the code, call FullScanPage or ScanPage with the Windows Bitmap object containing your image. The included TestApp (written in VB.NET) demonstrates the basic use:

Dim barcodes As New System.Collections.ArrayList
BarcodeImaging.FullScanPage(barcodes, Me.PictureBox1.Image, 100)
If barcodes.Count > 0 Then
  ' Found one or more barcodes ...

The numscans parameter in both functions indicates how many bands of pixels should be scanned across or down the image. With a higher number, the code finds more barcodes, but of course, will also run slightly slower. Usually 50 - 100 scans will be OK to find all barcodes on a full page image.

Difference between FullScanPage and ScanPage

FullScanPage always scans horizontally and vertically, and attempts to detect all supported barcode types. If you know that your input material is always scanned in the same orientation, or if you do not need detection of all barcode types, you can make your program run faster by using ScanPage.

public static void ScanPage(ref System.Collections.ArrayList CodesRead, 
       Bitmap bmp, int numscans, ScanDirection direction, BarcodeType types)

With the additional parameters direction and types, you can fine-tune barcode detection:

  • direction: can be ScanDirection.Vertical or ScanDirection.Horizontal. Use Vertical for detecting barcodes with vertical bars, or Horizontal if you expect barcodes that are rotated 90 degrees.
  • types: Pass BarcodeType.All to detect all supported barcode types, or you can specify one or more specific barcode types, like this:
    ScanPage(ref CodesRead, bmp, numscans, ScanDirection.Vertical,
             BarcodeType.Code39 | BarcodeType.Code128);

    Supported types are Code39, EAN, and Code128. The EAN reader will also detect UPC codes.

Points of interest

  • The EAN reader also reads the 2 or 5 digits supplemental barcodes often found on books and periodicals. As shown in the screenshot, a supplemental barcode will be returned as a separate barcode string starting with "S".
  • The Code128 reader has mixed code page support. The serial number in the sample image Code128test-CodeC.png starts as Code C, but the last digit is added as Code B.
  • The code uses a more advanced approach for measuring the "narrow bar width" than qlipoth's and Liedblad's versions. This should allow for better detection rates when reading EAN and Code128. In Code39, we only need to distinguish between narrow and wide bars, but the other barcode types use four different bar widths.
  • I have added the concept of "barcode zones", to allow detection of differently scaled barcodes on the same scan line. In Code128test-CodeC.png, this enables the software to read both the serial number and the UPC code that are printed side-by-side.

    barcode zones

References

I used the following references while writing this project:

  1. For implementing EAN detection: Wikipedia articles on the European Article Number, EAN-2, and EAN-5.
  2. For implementing Code 128: the character table and checksum calculation as published on code128barcodes.com, and the barcode generator published by IDAutomation.com Inc., for testing.

History

  • October 5, 2009: Original.
  • October 19, 2009: Improved Code39 detection, bugfixes. Added VB.NET translation of the barcode detection class and the COM interface provided by Alessandro Gubbiotti.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Berend Engelbrecht
Software Developer (Senior) Decos Software Engineering BV
Netherlands Netherlands
No Biography provided

Comments and Discussions

 
GeneralMiles Behind Pin
tonym00112-Nov-09 13:11
membertonym00112-Nov-09 13:11 
GeneralRe: Miles Behind Pin
hground24-Nov-09 3:28
memberhground24-Nov-09 3:28 
GeneralRe: Miles Behind Pin
tonym00127-Nov-09 10:58
membertonym00127-Nov-09 10:58 
AnswerRe: Miles Behind Pin
Berend Engelbrecht27-Nov-09 23:05
memberBerend Engelbrecht27-Nov-09 23:05 
GeneralRe: Miles Behind Pin
tonym0014-Dec-09 13:50
membertonym0014-Dec-09 13:50 
GeneralReading Barcodes : some doubt ... Pin
beguroto2-Nov-09 22:17
memberbeguroto2-Nov-09 22:17 
GeneralRe: Reading Barcodes : some doubt ... Pin
Berend Engelbrecht3-Nov-09 6:26
memberBerend Engelbrecht3-Nov-09 6:26 
GeneralBar widths Pin
supercat928-Oct-09 12:22
membersupercat928-Oct-09 12:22 
If barcodes will be surrounded by quiet zones, such that one can identify the beginning and end of any suspected barcode before one has to worry about trying to decode it, one can easily narrow down the possibilities for barcode type and compute bar/space widths without fancy histogram techniques.

For example, if there are 5n+4 bars between quiet zones (for some value n), the code might be an I2of5 barcode containing 2n+1 wide bars and 3n+3 narrow ones, along with 2n wide spaces and 3n+3 narrow ones. If one expects a 2:1 wide/narrow ratio, one can figure that the narrow bar width should be the total width of the black areas, divided by (7n+5). Likewise the narrow space width should be the total space of the white areas (not counting quiet zones) divided by (7n+3). If the number of bars isn't 5n+4, the code isn't I2of5, so there's no need to parse any further.

For Code39, the number of bars must be a multiple of five, and the bars should be processed in groups of five. There are two types of Code39 barcode (two wide and three narrow bars, plus one wide and three narrow spaces, or else five narrow bars, and three wide and one narrow spaces). If less than half the area within a symbol is white, it's the former style; if more than half, the latter. Once the style is determined, the wide/narrow widths for bars and spaces may be ascertained.

This approach is nicely amenable to things like Code128 which have multiple bar/space widths. Because the 'ink density' of Code 128 isn't constant, it's necessary to compute the module width based upon total symbol width, without using total white width and total black width separately. This makes it harder to factor out the effects of printers that cause black areas to come out wider or narrower than they should, but is much easier than using histograms.
GeneralRe: Bar widths Pin
Berend Engelbrecht28-Oct-09 13:03
memberBerend Engelbrecht28-Oct-09 13:03 
QuestionPossible to integrate scew angle? Pin
infal23-Oct-09 4:14
memberinfal23-Oct-09 4:14 
AnswerRe: Possible to integrate scew angle? Pin
Berend Engelbrecht23-Oct-09 22:25
memberBerend Engelbrecht23-Oct-09 22:25 
GeneralRe: Possible to integrate scew angle? Pin
infal24-Oct-09 6:54
memberinfal24-Oct-09 6:54 
GeneralRe: Possible to integrate scew angle? [Modified: proposed strategy for detecting skewed/rotated barcodes] Pin
Berend Engelbrecht24-Oct-09 7:05
memberBerend Engelbrecht24-Oct-09 7:05 
GeneralThank you Pin
babakzawari23-Oct-09 3:11
memberbabakzawari23-Oct-09 3:11 
QuestionSupport for rotaded, skewed low resoluted images? Pin
infal22-Oct-09 23:15
memberinfal22-Oct-09 23:15 
AnswerRe: Support for rotaded, skewed low resoluted images? Pin
Berend Engelbrecht22-Oct-09 23:30
memberBerend Engelbrecht22-Oct-09 23:30 
GeneralTIFF support Pin
ndisampson22-Oct-09 18:40
memberndisampson22-Oct-09 18:40 
GeneralRe: TIFF support [modified] Pin
Berend Engelbrecht22-Oct-09 19:18
memberBerend Engelbrecht22-Oct-09 19:18 
GeneralCool but does not allways work... Pin
infal22-Oct-09 2:25
memberinfal22-Oct-09 2:25 
GeneralRe: Cool but does not allways work... Pin
Berend Engelbrecht22-Oct-09 2:31
memberBerend Engelbrecht22-Oct-09 2:31 
GeneralRe: Cool but does not allways work... [modified] Pin
infal22-Oct-09 6:36
memberinfal22-Oct-09 6:36 
GeneralCause of problem and bugfix PinPopular
Berend Engelbrecht22-Oct-09 8:45
memberBerend Engelbrecht22-Oct-09 8:45 
GeneralRe: Cause of problem and bugfix Pin
infal22-Oct-09 23:16
memberinfal22-Oct-09 23:16 
GeneralRe: Cause of problem and bugfix Pin
hairy_hats28-Mar-11 1:44
memberhairy_hats28-Mar-11 1:44 
GeneralLooks really cool! Pin
Shane Story7-Oct-09 3:07
memberShane Story7-Oct-09 3:07 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

Article
Posted 5 Oct 2009

Stats

913.4K views
87.4K downloads
412 bookmarked