Barcode library or Barcode SDK is a software library that can be used to add barcode features to desktop, web, mobile or embedded applications. Barcode library presents sets of subroutines or objects which allow to create barcode images and put them on surfaces or recognize machine-encoded text / data from scanned or captured by camera images with embedded barcodes. The library can support two modes: generation and recognition mode, some libraries support barcode reading and writing in the same way, but some libraries support only one mode.

At this time barcode technology allows to add machine reading tags or machine reading additional data to any object of real world with less than one cent cost. and use any of camera equipped device to identify additional data about an object. In this way, combination of barcode technology and barcode library allows to implement with low cost any automatic document processing application, OMR application, package tracking application or even augmented reality application.

The first Barcode SDKs were not implemented as software libraries but as standalone applications for MS-DOS and Windows and as Barcode fonts. At that time barcodes were used mostly in retail and for internal corporation needs, thus barcode users looked for all-inclusive hardware solutions to generate, print and recognize barcodes.

The situation changed when camera equipped devices (like mobile phones) and document scanners became common for everyday usage. Because barcodes could be scanned and recognized on common ordinary equipment and industrial and office users did not need to obtain expensive specialized one-function devices for barcode reading, the need for barcode writing and reading SDKs and libraries increased.

Barcode writing libraries already had been implemented as barcode fonts or standalone applications in projects like GNU Barcode or Zint. Implementation of a barcode writing library does not require hard Computer Science skills because it just need to follow AIM or ISO specifications. It does not have any difference from encoding data in special file format.

2D barcodes encoding is more difficult because 2D barcodes instead of 1D barcodes have additional encoding data like columns, rows, ECI or data correction options. Some 2D barcodes like MaxiCode or Pdf 417 also have special encoding fields like Post Address or metadata which convert these barcodes in multiple graphical files. These differences could not be solved by barcode fonts usage and required API with multiple parameters processing.

Barcode reading libraries are more complex, requiring Computer Vision techniques. However, they can be run on common camera or scanner equipped devices. The first libraries could recognize only 1D barcodes by laser scanners mode emulation. This mode captured the whole image but then library made some scan-lines with Bresenham's algorithm and tried to recognize data from these lines as hardware laser scanners did. The bright representation of these libraries is early ZXing project supported by Google, ZBar or other solutions.

For the recognition of 2D barcodes laser scanners mode emulation is not suitable. Moreover, this method has difficulty with barcode area detection, which causes problems with 1D angled barcode detection. More complicated methods from Computer Vision were implemented to improve recognition quality for 1D and 2D barcodes.