Creating EAN-13 Barcodes with C#

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Introduction

This article came about as a response to a request to extend the UPC-A barcode example to include EAN-8 and EAN-13. In this article, we will look at the EAN-13 specification and examine some code that can produce EAN-13 barcodes.

EAN-13 Background

The EAN-13 barcode is composed of 13 digits, which are made up of the following sections: the first 2 or 3 digits are the country code, the next 5 to 7 digits are the manufacturer code, the next 3 to 5 digits are the product code, and the last digit is the checksum digit.

The figure below shows a typical EAN-13 barcode.

Country Code

The Country Code is a 2 or 3 digit number, which is used to identify the country that assigned the manufacturer code. All EAN-13 barcodes that begin with "0" are UPC-A barcodes. The following table contains the Country Codes:

Manufacturer Code

The EAN Manufacturer Code is a variable length number. Typically, 5 digit codes are assigned to companies, however, some companies do not produce enough products to warrant a 5 digit product code, and in such cases the EAN will issue Manufacturer Codes longer than 5 digits.

Product Code

The manufacturer is free to assign its own product codes, but they must make sure that each product code is unique within their product codes. The product codes can be as few as 3 digits long, or as long as 5 digits depending on the length of the country and manufacturer codes.

Checksum Digit

The checksum digit is calculated using the country code, manufacturer's code, and the product code. The odd numbers starting with the right most digits are multiplied by 3 and added to the sum, while the even numbers are simply added to the sum. The reason for the EAN-13 check sum being calculated in reverse order (starting with the right most digit and considering it as being odd instead of even) is for compatibility with UPC-A barcodes. The modulus of 10 is then taken of the summed total. This is subtracted from 10, and the modulus of 10 is taken again.

Symbol Size

The specifications for the EAN-13 barcode specify the nominal size as 37.29mm wide and 25.93mm high. Based upon this nominal size, the EAN-13 barcode can be scaled by a magnification factor of 0.8 to 2.0. Scaling the barcode will produce a barcode between the minimal allowable size of 29.83mm wide by 20.74mm high and the maximum allowable size of 74.58mm wide and 51.86mm high.

Digit Patterns

Each digit in a EAN-13 bar code is composed of a series of two spaces and two bars. Each digit is drawn within a space that is 7 modules wide. In addition to the 13 digits, which make up a EAN-13 barcode, the barcode symbol also has two quite zones, a lead block, a separator, and a trailing block. Each quite zone is 9 modules wide, the lead and trailing blocks are a series of lines and spaces in the format of bar, space, bar. The separator is signified by the sequence space / bar / space / bar / space.

In addition to the special symbol patterns listed above, the EAN-13 barcode symbol uses three distinct digit patterns as well, the Left Digit Odd Parity pattern, the Left Digit Even Parity pattern and the Right Digit pattern. The Left Digit patterns start with spaces, and the Right Digit pattern starts with bars (see table below).

where a '0' denotes a space and '1' represents a bar.

The first digit of the Country Code is used to determine the parity of each digit of the Manufacturer's Code, see the Determining Number Parity section. The Right Digit pattern is typically used to draw the product code and the checksum digit. However, it will be used to render part of the manufacturer's code if the country code is greater than 2, or if the manufacturer's code is greater than 5.

Determining Number Parity

The first digit of the Country Code in an EAN-13 barcode is not encoded, it is used to determine the parity of the digits in the manufacturer code. The second digit of the country code is always odd and the manufacturer's code will have three left-hand numbers that use even parity and two that use odd parity, except a UPC-A compatible barcode which uses all odd parity. The table below outlines the parity for the numbers in the Manufacturer's Code.

For example, if the country code is 75 then based upon the 1^st country code digit and the above table, the 2^nd digit of the country code, 5, would be Odd. The 1^st digit of the Manufacturer Code would use the Even pattern, the 2^nd digit would use the Odd pattern, the 3^rd digit would use the Even pattern, the 4^th would be Odd, and finally the 5^th digit would use the Even pattern.

Using the code

First, we will examine how to use the Ean13 class, and then we'll examine how the Ean13 class works.

Using the Ean13 Class

The code excerpt below uses the Ean13 class to draw a EAN-13 barcode in a picture box control:

private void DrawEan13( )
{        
    System.Drawing.Graphics g = this.picBarcode.CreateGraphics( ); 

    g.FillRectangle(
         new System.Drawing.SolidBrush(System.Drawing.SystemColors.Control), 
         new Rectangle(0, 0, picBarcode.Width, picBarcode.Height)); 
        
    // Create an instance of the Ean13 Class.        

    upc = new Ean13( ); 
    
    upc.CountryCode = "12";
    upc.ManufacturerCode = "34567"; 
    upc.ProductCode = "89012"; 
    upc.Scale = 
        (float)Convert.ToDecimal(cboScale.Items [cboScale.SelectedIndex]); 
    
    upc.DrawEan13Barcode( g, new System.Drawing.Point( 0, 0 ) ); 
    
    g.Dispose( );
}

The first step for the DrawEan13 function is to create an instance of the Ean13 class, and then set the country code, manufacturer code, the product code, and the scale factor properties (the check sum will be calculated by the Ean13 class). Once these properties are set, a call to the DrawEan13Barcode function is made, passing a Graphics object and a Point, which indicates the starting position to draw at, this will cause the barcode to be drawn in the picture box starting at point (0, 0).

The Ean13 Class

The most significant variables are listed below:

// This is the nomimal size recommended by the EAN.

private float _fWidth = 37.29f;
private float _fHeight = 25.93f;
private float _fFontSize = 8.0f;
private float _fScale = 1.0f;

// Left Hand Digits.

private string [] _aOddLeft = { "0001101", "0011001", "0010011", "0111101", 
                                "0100011", "0110001", "0101111", "0111011", 
                                "0110111", "0001011" };

private string [] _aEvenLeft = { "0100111", "0110011", "0011011", "0100001", 
                                 "0011101", "0111001", "0000101", "0010001", 
                                 "0001001", "0010111" };

// Right Hand Digits.

private string [] _aRight = { "1110010", "1100110", "1101100", "1000010", 
                              "1011100", "1001110", "1010000", "1000100", 
                              "1001000", "1110100" };

private string _sQuiteZone = "000000000";

private string _sLeadTail = "101";

private string _sSeparator = "01010";

The _fWidth, _fHeight, and the _fScale variables are initialized with the nominal size. When the barcode is rendered, its actual size will be determined by the nominal size, and the scale factor, as discussed in the Symbol Size section of this article. The variables _aOddLeft, _aEvenLeft, _aRight, _sQuiteZone, _sLeadTail, and _sSeparator are all string representations of the bar/space graphics, which represent the various parts of an EAN-13 barcode. Essentially, a '1' represents a bar and a '0' represents a space, so _sSeparator would cause a space-bar-space-bar-space to be rendered. An alternate method to using a string could be to use a binary representation, where a 0 bit would be a space and a 1 bit is a bar.

There are four primary functions which provide the majority of the functionality for the Ean13 class. The workhorse of these functions is DrawEan13Barcode, which uses several functions as helper functions. The helper functions are: CalculateChecksumDigit, ConvertToDigitPatterns, ConvertLeftPattern which will be discussed first. There is also a fifth function, CreateBitmap, which provides an easy means for creating a bitmap image.

The first helper function DrawEan13Barcode calls the CalculateChecksumDigit function, which uses the country code, manufacturer code, and product code to calculate the barcode's check sum.

public void CalculateChecksumDigit( )
{
    string sTemp = 
      this.CountryCode + this.ManufacturerCode + this.ProductCode;
    int iSum = 0;
    int iDigit = 0;

    // Calculate the checksum digit here.

    for( int i = sTemp.Length; i >= 1; i-- )
    {
        iDigit = Convert.ToInt32( sTemp.Substring( i - 1, 1 ) );
        // This appears to be backwards but the 

        // EAN-13 checksum must be calculated

        // this way to be compatible with UPC-A.

        if( i % 2 == 0 )
        { // odd  

            iSum += iDigit * 3;
        }  
        else 
        { // even

            iSum += iDigit * 1; 
        }
    }
    int iCheckSum = ( 10 - ( iSum % 10 ) )  % 10; 
    this.ChecksumDigit = iCheckSum.ToString( );
}

The CalculateChecksumDigit function calculates the check sum using the method discussed in the Checksum Digit section listed above.

The second helper function used is the ConvertToDigitPatterns function. This function takes the individual numbers of the manufacturer code, and the product number, and converts them to the string representation of the barcode graphics.

private string ConvertToDigitPatterns(string inputNumber, string [] patterns)
{
    System.Text.StringBuilder sbTemp = new StringBuilder( );
    int iIndex = 0;
    for( int i = 0; i < inputNumber.Length; i++ )
    {
        iIndex = Convert.ToInt32( inputNumber.Substring( i, 1 ) );
        sbTemp.Append( patterns[iIndex] );
    }
    return sbTemp.ToString( );
}

The ConvertToDigitPatterns function requires two parameters:

• inputNumber
• patterns

The inputNumber will be either the manufacturer number, or the product number, and the patterns will be the _aOddLeft, _aEvenLeft, or the _aRight array depending on whether the inputNumber is the manufacturer number or the product number.

The ConvertLeftPatterns is used to create the left hand patterns discussed in the Determining Number Parity section. The ConvertLeftPatterns determines the country code, and calls the appropriate country code converter.

private string ConvertLeftPattern( string sLeft )
{
    switch( sLeft.Substring( 0, 1 ) )
    {
        case "0":
            return CountryCode0( sLeft.Substring( 1 ) );
            
         case "1":
            return CountryCode1( sLeft.Substring( 1 ) );

         case "2":
            return CountryCode2( sLeft.Substring( 1 ) );

         case "3":
            return CountryCode3( sLeft.Substring( 1 ) );

         case "4":
            return CountryCode4( sLeft.Substring( 1 ) );

         case "5":
            return CountryCode5( sLeft.Substring( 1 ) );

         case "6":
            return CountryCode6( sLeft.Substring( 1 ) );

         case "7":
            return CountryCode7( sLeft.Substring( 1 ) );

         case "8":
            return CountryCode8( sLeft.Substring( 1 ) );

         case "9":
            return CountryCode9( sLeft.Substring( 1 ) );

         default:
            return "";
    }
}

Each country code has its own separate converter function. CountryCode0 is a UPC-A barcode so it will use only the left hand odd parity patterns. CountryCode1 through CountryCode9 each uses the appropriate parity patterns discussed in the Determining Number Parity section. See the CountryCode1 code below for an example of a country code converter function:

private string CountryCode1( string sLeft )
{
    // 1 Odd Odd  Even Odd  Even Even 

    System.Text.StringBuilder sReturn = new StringBuilder( );
    sReturn.Append( ConvertToDigitPatterns( sLeft.Substring( 0, 1 ), 
                                                     this._aOddLeft ) );
    sReturn.Append( ConvertToDigitPatterns( sLeft.Substring( 1, 1 ), 
                                                     this._aOddLeft ) );
    sReturn.Append( ConvertToDigitPatterns( sLeft.Substring( 2, 1 ), 
                                                     this._aEvenLeft ) );
    sReturn.Append( ConvertToDigitPatterns( sLeft.Substring( 3, 1 ), 
                                                     this._aOddLeft ) );
    sReturn.Append( ConvertToDigitPatterns( sLeft.Substring( 4, 1 ), 
                                                     this._aEvenLeft ) );
    sReturn.Append( ConvertToDigitPatterns( sLeft.Substring( 5, 1 ), 
                                                     this._aEvenLeft ) );
    return sReturn.ToString( );
}

The CountryCode1 function uses the parity patterns discussed in the Determining Number Parity section to send each number to the ConvertToDigitPatterns function with the correct left hand pattern. The sLeft parameter should contain the 2^nd digit of the Country Code and the Manufacturer's Code.

Finally the workhorse; the DrawEan13Barcode handles the rendering of the barcode graphics and requires two parameters:

• g
• pt

This function begins by determining the width and height for the barcode by scaling the nominal width and height by the scale factor. The lineWidth is based upon the total number of modules required to render an EAN-13 barcode. The total number of modules, 113, is determined by the following: for example:

EAN-13 code - 1234567890128

To determine the total module width, simply add the individual parts: 9 + 3 + 7 + 35 + 5 + 35 + 7 + 3 + 9 = 113. The 2^nd digit of the Country code, 2, will have an odd parity, the 1^st digit of the manufacturer's code, 3, will use the Odd pattern, the 2^nd digit, 4, will use the Even pattern, the 3^rd digit, 5, would use the Odd pattern, the 4^th and 5^th digits, 6 and 7, would use the Even pattern.

public void DrawEan13Barcode(System.Drawing.Graphics g, System.Drawing.Point pt)
{ 
    float width = this.Width * this.Scale;
    float height = this.Height * this.Scale;

    //    EAN13 Barcode should be a total of 113 modules wide.

    float lineWidth = width / 113f;

    // Save the GraphicsState.

    System.Drawing.Drawing2D.GraphicsState gs = g.Save( );

    // Set the PageUnit to Inch because all of 

    // our measurements are in inches.

    g.PageUnit = System.Drawing.GraphicsUnit.Millimeter;

    // Set the PageScale to 1, so a millimeter 

    // will represent a true millimeter.

    g.PageScale = 1;

    System.Drawing.SolidBrush brush = 
        new System.Drawing.SolidBrush(System.Drawing.Color.Black);

    float xPosition = 0;

    System.Text.StringBuilder strbEAN13 = new System.Text.StringBuilder( );
    System.Text.StringBuilder sbTemp = new System.Text.StringBuilder( );

    float xStart = pt.X;
    float yStart = pt.Y;
    float xEnd = 0;

    System.Drawing.Font font = 
         new System.Drawing.Font("Arial", this._fFontSize * this.Scale);

    // Calculate the Check Digit.

    this.CalculateChecksumDigit( );

    sbTemp.AppendFormat( "{0}{1}{2}{3}", 
                        this.CountryCode,
                        this.ManufacturerCode,
                        this.ProductCode, 
                        this.ChecksumDigit );


    string sTemp = sbTemp.ToString( );

    string sLeftPattern = "";

    // Convert the left hand numbers.

    sLeftPattern = ConvertLeftPattern(sTemp.Substring( 0, 7 ));

    // Build the UPC Code.

    strbEAN13.AppendFormat( "{0}{1}{2}{3}{4}{1}{0}",
               this._sQuiteZone, this._sLeadTail,
               sLeftPattern, this._sSeparator,
               ConvertToDigitPatterns(sTemp.Substring( 7 ), this._aRight));

    string sTempUPC = strbEAN13.ToString( );

    float fTextHeight = g.MeasureString( sTempUPC, font ).Height;

    // Draw the barcode lines.

    for( int i = 0; i < strbEAN13.Length; i++ )
    {
        if( sTempUPC.Substring( i, 1 ) == "1" )
        {
            if( xStart == pt.X )
                xStart = xPosition;

            // Save room for the UPC number below the bar code.

            if( ( i > 12 && i < 55 ) || ( i > 57 && i < 101 ) )
                // Draw space for the number

                g.FillRectangle( brush, xPosition, yStart, 
                                       lineWidth, height - fTextHeight );
            else
                // Draw a full line.

                g.FillRectangle( brush, xPosition, yStart, lineWidth, height );
        }

        xPosition += lineWidth;
        xEnd = xPosition;
    }

    // Draw the upc numbers below the line.

    xPosition = 
      xStart - g.MeasureString(this.CountryCode.Substring( 0, 1 ), font).Width;
    float yPosition = yStart + ( height - fTextHeight );

    // Draw 1st digit of the country code.

    g.DrawString( sTemp.Substring( 0, 1 ), font, brush, 
         new System.Drawing.PointF( xPosition, yPosition ) );

    xPosition += 
      (g.MeasureString(sTemp.Substring( 0, 1 ), font).Width + 43 * lineWidth) -
                 (g.MeasureString( sTemp.Substring( 1, 6 ), font ).Width);

    // Draw MFG Number.

    g.DrawString( sTemp.Substring( 1, 6 ), font, brush, 
         new System.Drawing.PointF( xPosition, yPosition ) );

    xPosition += 
      g.MeasureString(sTemp.Substring( 1, 6 ), font).Width + (11 * lineWidth);

    // Draw Product ID.

    g.DrawString( sTemp.Substring( 7 ), font, brush, 
         new System.Drawing.PointF( xPosition, yPosition ) );

    // Restore the GraphicsState.

    g.Restore( gs );
}

The function uses the CalculateChecksumDigit function to calculate the correct check sum digit, next the call to ConvertLeftPatterns is made, and then the ConvertToDigitPatterns function is used to convert the product code and check sum number of the EAN-13 barcode number to a string representation. Once the number has been converted over to a string representation, the code uses the string representation to render the barcode, 1 will cause a rectangle to be drawn, and 0 will cause the code to skip drawing a rectangle. If the code draws a rectangle, it also takes into consideration whether it needs to shorten the rectangle to allow space for the manufacturer's number and the product number. Once the barcode is completely rendered, the code then determines the position, and draws the country code, the manufacturer's number, the product number, and the check sum digit.

The CreateBitmap function simply creates a Bitmap object, and uses the DrawEan13Barcode function to render the barcode to the Bitmap object, and then it returns the Bitmap.

public System.Drawing.Bitmap CreateBitmap( )
{
    float tempWidth = ( this.Width * this.Scale ) * 100 ;
    float tempHeight = ( this.Height * this.Scale ) * 100;

    System.Drawing.Bitmap bmp = 
        new System.Drawing.Bitmap( (int)tempWidth, (int)tempHeight );

    System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bmp);
    this.DrawEan13Barcode( g, new System.Drawing.Point( 0, 0 ) );
    g.Dispose( );
    return bmp;
}

Special Thanks

I would like to thank m@u for pointing out the flaw in my original article and source code. I would also like to thank MArmbruckner for testing version 2.0 and making sure the barcodes would scan properly.

History

• Version 1.0 - Initial application.
• Version 2.0 - Revised application to use the correct barcode patterns based on the 1^st digit of the country code.