Reading Barcode Properties and Metadata


Aspose.BarCode for Python via .NET not only enables reading information encoded in a barcode but also provides a possibility to analyze its technical properties, including barcode type, orientation angle, position, and metadata. This data is stored in objects of class BarCodeResult and can be fetched using properties described further in this article.

Barcode Type and Encoded Data

To obtain input barcode data and its type, code_text and code_type properties of class BarCodeResult can be used. The other property called code_type_name returns the text name of the barcode type.

Barcode Position and Orientation Angle

To obtain the position of a source barcode and its orientation angle, class BarCodeRegionParameters can be used. This class allows getting the information about the barcode region in the following forms:

  • quadrangle – a quadrangle object that bounds a barcode
  • rectangle - a rectangle object that bounds a barcode
  • points – an array of points constituting a barcode
  • angle – an orientation angle in degrees

Reading Barcode Data as Byte Stream

It is possible to load barcode data as a byte stream using a property of class BarCodeResult that is called code_bytes.

Quality Check of Recognition Results

Developers may need to check whether barcode reading outputs are accurate and complete. For this purpose, class BarCodeResult contains two properties: confidence and reading_quality.
Depending of the quality of barcode reading results, the confidence property returns a instance of the BarCodeConfidence enum that denotes the recognition confidence level. This enumeration contains values STRONG, NONE, and MODERATE that are discussed below. The reading_quality property returns an estimate of recognition quality corresponding to the confidence level, as explained in the table below.

Confidence Level Quality Value Description
NONE 0 If the confidence level is None, it indicates that the barcode is invalid and its information has been read with errors. If required, it is possible to get its type and position in the image and decode barcode information partially
MODERATE 80 This confidence level may be returned for linear and postal barcode types with weak or absent checksum controls. Furthermore, it is necessary to analyze the result of the reading_quality property. The absolute correctness of barcode reading results is not assured
STRONG 100 This confidence level is returned for all 2D types with Reed-Solomon error correction. It means that barcode text has been recognized accurately

Barcode Metadata

Reading Metadata from 1D Barcodes

Some 1D barcode types, i.e. EAN 13, allow separating barcode input information itself from the checksum value. To do this, class OneDExtendedParameters provides the value property that allows getting 1D barcode text and the check_sum property that returns the result of checksum computation.

Reading Metadata from QR Codes with Structured Append

To fetch metadata from QR Code barcodes with structured append, the barcode library provides a class called QRExtendedParameters that enables reading the information from structured append used to combine several QR Code barcodes into one. This data can be obtained using the following properties:

  • qr_structured_append_mode_bar_code_index - returns the sequence number of the current barcode (starting from 0)
  • qr_structured_append_mode_bar_codes_quantity - returns the number of barcodes in a composite QR Code barcode taht can take values from 2 to 16
  • qr_sructured_append_mode_parity_data - returns the checksum identifier byte that is usually computed as XOR of all bytes in which UTF16BE characters are encoded in two bytes

Getting Raw Data from Code 128 Barcodes

Input data stored in Code 128 barcodes can be encoded in three ways: A, B, or C. Class Code128ExtendedParameters provides a property called code_128_data_portions that returns decoded parts of barcode input information and the encoding mode.

Reading Metadata from DataBar Barcodes with 2D Components

Metadata from DataBar barcodes with 2D components can be obtained using class called DataBarExtendedParameters that provides a property called is_2d_composite_component. This property allows enabling or disabling a 2D component in DataBar barcodes.

Reading Macro PDF417 and Macro PDF417 Metadata

Metadata from PDF417 barcodes can be obtained using the properties of class Pdf417ExtendedParameters listed below.

PDF417 Metadata Property Description
pdf_417_macro_file_id Gets the unique identifier of a barcode series or a PDF417 file
pdf_417_macro_segment_id Gets the current identifier of a segment
pdf_417_macro_segments_count Returns the number of barcodes in a series
pdf_417_macro_file_name Returns the name of a file
pdf_417_macro_checksum Gets the checksum value computed using CCITT-16 polynomial
pdf_417_macro_file_size Returs the total size of bytes in a series
pdf_417_macro_time_stamp Returns the time spent to generate/send the file
pdf_417_macro_addressee Gets the address of the file sender
pdf_417_macro_sender Returns the name of the file sender

Decoding Barcode Text in Unicode

For barcodes in which the barcode data is encoded in a Unicode encoding, the barcode library provides the get_code_text(encoding) method that can be used to enable the required encoding.