GS1-128/Code 128 barcode encoder

This is a simple GS1-128 barcode encoder library. The reason to choose it over others is simply that it is written in pure C code and has no external dependencies. That's right - it doesn't even depend on a graphics library. As a bonus, the barcodes produced by this program will automatically use the Code 128 A, B, or C modes based on what generates the shortest barcode.

Here's how to use:

    const char *str = "[FNC1] 00 12345678 0000000001";
    size_t barcode_length = code128_estimate_len(str);
    char *barcode_data = (char *) malloc(barcode_length);
    int i;

    barcode_length = code128_encode_gs1(str, barcode_data, barcode_length);

    /* barcode_length is now the actual number of "bars". */
    for (i = 0; i < barcode_length; i++) {
        if (barcode_data[i])
            draw_vertical_bar_at_column(i);
    }

Once you get barcode_data, each byte corresponds to whether a vertical line should be drawn. If the byte is 0xff, then draw a line. If the byte is 0x00, then don't.

Compiling and testing

The main library, code128.[ch], doesn't have any dependencies. The test program depends on libpng, so make sure to install that first. On Debian/Ubuntu, run:

sudo apt install libpng-dev

Then run make. The result is a test program that creates png files of barcode data passed on the commandline.

The regression tests require zbar. Install zbar on Debian/Ubuntu by:

sudo apt install zbar-tools

Or on OSX:

brew install zbar

Then run make check.

Integrating

If you're using C or C++, the easiest way of integrating this code into your program is to just copy code128.[ch] to your tree. If you're not using C, then calling code128png from your app may be an option as well.