Reading Barcode Properties and Metadata
Overview
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.