Barcode Objects

Barcode Objects

command. While a text object is active, commands that alter text line attributes (such as font and double-height character commands) are ignored. Commands that alter text character attributes (such as double wide and inverse) may be sent at any time.

Line attributes include the five basic fonts (ESC S, P, M, U, and T), plus the double-height font command (GS DC2). These commands may not be issued while a text object is active; instead they should be issued before a text object is begun. The font line attribute persists until another font command is received. The double-height line attribute persists either until the cancel double-height command (GS DC3) is sent or the current font is changed.

The character attribute commands include the set font to double wide (SO) and set inverse print mode (GS RS) commands. These commands may be issued or canceled at any time. Character attributes persist only until the end of a text object.

A text object can be terminated with a carriage return, a line feed, or both, in either combination. If the length of the text object exceeds the space allowed for printing, it will either wrap to the next line or truncate at the end of the printable area. The decision to wrap or truncate is determined by the select line wrap/truncate mode command (GS T). By default, text objects will wrap to the next line.

A barcode object is created by the print barcode (GS k) command. Specified within the command is the symbology to be used, the amount of data to be encoded, and the data itself. Other attributes of the barcode, such as height and width, can be set using other commands.

The set barcode height (GS h) command specifies the height of the barcode in dots, or 1/8th mm. The maximum height for a barcode is 256 dots, or 32 mm. In cases where a taller barcode is needed, a second barcode can be printed below the first at the same left offset.

The set barcode module width (GS w) and set barcode element width (GS W) commands can be used to alter the width of the barcode. See the command descriptions for a full explanation of the differences between these two commands.

The POSTNET barcode symbology is an exception and does not respond to any of these commands. Instead, it always prints within the U.S. Postal Service’s specifications.

The limitations of each symbology must be adhered to when sending data for a barcode. For example, you should not send alphabetic characters to symbologies that only accept numeric data (like the UPC/EAN symbology).

Other items must also be considered when printing barcodes. You must leave sufficient blank space on either side of the barcode to create a quiet zone. You must also select a good ratio/element size if the default values are not being used, and you must allow adequate room for the barcode to be printed on the label. If you ignore any of these items, the barcode that is printed may be unreadable.

In general, you should be very familiar with using barcodes if you want to ensure success.

A barcode object is self-terminating and will be processed as soon as it has received the last byte of data required to define to it. The print barcode (GS k) command’s second