Smoky Cogs

UPC-5 is a variation on the UPC-A barcode designed to contain 5 digits of data.

UPC-5 Barcode

Calculating the parity uses the same modulo 10 method as the UPC-A, except that the weightings are different. Odd-numbered positions are weighted 3, while even-numbered positions are weighted 9.

Once we have the weighted sum, we apply a modulo 10 to the weighted sum, which gets the remainder after applying a modulo of 10 to the weighted sum.

The parity is then 10 – (modulo 10 of the weighted sum).

UPC-5 only has a left guard and centre guard (which is places after the third digit), which are encoded as 1011 and 01 respectively.

The 5 digits are then encoded using either odd or even encoding, which is determined by the parity string.

The odd and even encodings are the same as the ones for the UPC-E format

Here is the code to encode the barcode. The full source code is available here

namespace BarcoderLib
{
    public class BarcodeUPC5 
    {
        private string gLeftGuard = "1011";
        private string gCentreGuard = "01";
        private string[] gOdd = { "0001101", "0011001", "0010011", "0111101", "0100011", "0110001", "0101111", "0111011", "0110111", "0001011" };
        private string[] gEven = { "0100111", "0110011", "0011011", "0100001", "0011101", "0111001", "0000101", "0010001", "0001001", "0010111" };
        private string[] gParity = {"00111", "01011", "01101", "01110", "10011", "11001", "11100", "10101", "10110", "11010"};

        private int[] gWeighting = { 3, 9, 3, 9, 3};
    
        public Bitmap Encode(string message)
        {
            string encodedMessage;

            Bitmap barcodeImage = new Bitmap(250, 100);
            Graphics g = Graphics.FromImage(barcodeImage);


            Validate(message);
            encodedMessage = EncodeBarcode(message);

            PrintBarcode(g, encodedMessage, message, 250, 100);

            return barcodeImage;
        }
        private void Validate(string message)
        {

            Regex reNum = new Regex(@"^\d+$");
            if (reNum.Match(message).Success == false)
            {
                throw new Exception("Encode string must be numeric");
            }

            if (message.Length != 5)
            {
                throw new Exception("Encode string must be 5 digits long");
            }
        }

        private void PrintBarcode(Graphics g, string encodedMessage, string message, int width, int height)
        {
            SolidBrush whiteBrush = new SolidBrush(Color.White);
            SolidBrush blackBrush = new SolidBrush(Color.Black);
            Font textFont = new Font(FontFamily.GenericMonospace, 10, FontStyle.Regular);
            g.FillRectangle(whiteBrush, 0, 0, width, height);

            int xPos = 20;
            int yTop = 20;
            int barHeight = 50;

            for (int i = 0; i < encodedMessage.Length; i++)
            {
                if (encodedMessage[i] == '1')
                {
                    g.FillRectangle(blackBrush, xPos, yTop, 1, barHeight);
                }
                xPos += 1;
            }

            xPos = 20;
            yTop -= 17;
            for (int i = 0; i < message.Length; i++)
            {
                g.DrawString(message[i].ToString(), textFont, blackBrush, xPos, yTop);
                xPos += 7;
            }
        }

        private string EncodeBarcode(string message)
        {
            int i;
            int parityCode = CalcParity(message);
            char parity;
            string encodedString = gLeftGuard;

            for (i = 0; i < 5; i++)
            {
                parity = gParity[parityCode][i];
                if (parity == '1')
                {
                    encodedString += gOdd[Convert.ToInt32(message[i].ToString())];
                }
                else{
                    encodedString += gEven[Convert.ToInt32(message[i].ToString())];
                }
                if (i < 4)
                {
                    encodedString += gCentreGuard;
                }
            }

            return encodedString;
        }

        private int CalcParity(string message)
        {
            int sum = 0;
            int parity = 0;

            for (int i = 0; i < 5; i++)
            {
                sum += Convert.ToInt32(message[i].ToString()) * gWeighting[i];
            }

            parity = 10 - (sum % 10);
            if (parity == 10)
            {
                parity = 0;
            }
            return parity;
        }

    }
}