3. Using the Front End

Zint can be used to generate barcodes as PNG images or as encapsulated Post Script (EPS) files. This page describes how to encode data using the command line front end program.

3.1 Inputting data

The data to encode can be entered at the command line using the -d option, for example:

zint -d 'This Text'

This will encode the text This Text. Zint will use the default symbology, Code 128, and output to the default file out.png in the current directory.

3.2 Directing Output

Output can be directed to a file other than the default using the -o switch. For example:

zint -o here.png -d 'This Text'

draws a Code 128 barcode in the file here.png. If an encapsulated Post Script file is needed simply append the file name with .eps:

zint -o there.eps -d 'This Text'

Output can also be directed to stdout using the --directeps and --directpng switches for EPS and PNG output respectively.

3.3 Selecting barcode type

Selecting which type of barcode you wish to produce (i.e. which symbology to use) can be done at the command line using the -b or --barcode= switch followed by the appropriate integer value in the following table.

3.4 Adjusting height

The height of the symbol can be adjusted using the --height switch. For example:

zint --height=100 -d 'This Text'

specifies a symbol height of 100 times the x-resolution of the symbol.

3.5 Adjusting whitespace

The amount of whitespace to the left and right of the generated barcode can be altered using the -w switch. For example:

zint -w 10 -d 'This Text'

specifies a whitespace width of 10 times the x-resolution of the symbol.

3.6 Adding boundary bars and boxes

Zint allows the symbol to be bound with 'boundary bars' using the option --bind. These bars help to prevent misreading of the symbol by corrupting a scan if the scanning beam strays off the top or bottom of the symbol. Zint can also put a border right around the symbol and its whitespace with the --box option. This option is automatically chosen for ITF-14 symbols.

The width of the boundary or box can be specified using the --border switch. For example:

zint --box --border=10 -d 'This'

gives a box with a width 10 times the x-resolution of the symbol.

3.7 Using colour

The default colours of a symbol are a black symbol on a white background. Zint allows you to change this. The -r switch allows the default colours to be inverted so that a white symbol is shown on a black background. For example the command

zint -r -d 'This'

gives an inverted Code 128 symbol. This is not practical for most symbologies but white-on-black is allowed by the Data Matrix and Aztec Code symbology specifications.

For more specific needs the foreground and background colours can be specified using the --fg= and --bg= options followed by a number in RGB hexadecimal notation (the same system used in HTML). For example the command

zint --fg=004700 -d 'This'

alters the symbol to a dark green as shown below.

3.8 Rotating the Symbol

The symbol can be rotated through four orientations using the --rotate= option followed by the angle of rotation as shown below. This option is only available with PNG output.

3.9 Adjusting image size

The scale of the image can be altered using the --scale= option followed by a multiple of the default x-dimension. For example for PNG images a scale of 5 will increase the x-dimension to 10 pixels. Note that Maxicode symbols output as PNG images cannot be scaled in this way and that text added to a barcode in PNG images does not change size.

3.10 Handling NULL Characters

Some symbologies support encoding of the NULL character (ASCII 0) normally used to indicate the end of a character string. To support this functionality the --null= option allows you to substitute another character for NULL. Enter the decimal number for the character you wish to substitute. For example --null=21 instructs Zint to treat the NAK control character as a NULL character. Values between 1 and 128 are valid. This applies to Codablock-F, Code 128, Code 16k, Extended Code 39, Code 93, Maxicode, PDF417, MicroPDF417, Data Matrix (ECC 200 only) and Telepen.

3.11 Input modes

GS1 data can be encoded in a number of symbologies. Application identifiers are enclosed in [square brackets] followed by the data to be encoded (see 5.1.12.3). To encode GS1 data use --gs1. GS1 mode is assumed (and doesn't need to be set) for EAN-128, DataBar and Composite symbologies but is also available for Code 16k, Codablock-F, Data Matrix (ECC 200 only), and Aztec Code.

QR Code can encode Kaji characters. This can be accessed using the --kanji option.

3.12 Other options

Additional options are available which are specific to certain symbologies. These may, for example, control the quantity of error correction data or the size of the symbol. These options are discussed in section 5 of this guide.