Reading Barcode Properties and Metadata
Overview
Aspose.BarCode for Python via Java not only enables reading information encoded in a barcode but also provides a possibility to analyze its technical properties, including symbology, orientation angle, position, and metadata. This data is stored in objects of class BarCodeResult and can be fetched using special methods described further in this article.
Barcode Type and Encoded Data
To obtain input barcode data and its symbology, getCodeText and getCodeType methods of class BarCodeResult can be used. The other method called getCodeTypeName returns the text name of the barcode type.
Reading Barcode Data as Byte Stream
It is possible to load barcode data as a byte stream using a special method of class BarCodeResult that is called getCodeBytes.
Decoding Barcode Text in Unicode
For barcodes in which the barcode data is encoded in a Unicode encoding, the library provides the getCodeText method that can be used to enable the required encoding.
Quality Check of Recognition Results
Developers may need to check whether barcode reading outputs are accurate and complete. For this purpose, Aspose.BarCode for Python via Java provides two specific methods of class BarCodeResult: getConfidence and getReadingQuality.
Depending of the quality of barcode reading results, the getConfidence method 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 getReadingQuality method 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 symbology 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 getReadingQuality method. The absolute correctness of barcode reading results is not assured |
| STRONG | 100 | This confidence level is returned for all 2D symbologies with Reed-Solomon error correction. It means that barcode text has been recognized accurately |
Barcode Position and Orientation Angle
To obtain the position of a source barcode and its orientation angle, methods 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
Barcode Metadata
Reading Macro PDF417 and Macro PDF417 Metadata
Metadata from PDF417 barcodes can be obtained using methods of class Pdf417ExtendedParameters that are listed below.
| PDF417 Metadata Method | Description |
|---|---|
| getPdf417MacroFileID | Gets the unique identifier of a barcode series or a PDF417 file |
| getPdf417MacroSegmentID | Gets the current identifier of a segment |
| getPdf417MacroSegmentsCount | Returns the number of barcodes in a series |
| getPdf417MacroFileName | Returns the name of a file |
| getPdf417MacroChecksum | Gets the checksum value computed using CCITT-16 polynomial |
| getPdf417MacroFileSize | Returs the total size of bytes in a series |
| getPdf417MacroTimeStamp | Returns the time spent to generate/send the file |
| getPdf417MacroAddressee | Gets the address of the file sender |
| getPdf417MacroSender | Returns the name of the file sender |
Reading Metadata from QR Codes with Structured Append
To fetch metadata from QR Code barcodes with structured append, Aspose.BarCode for Python via Java provides a special class called QRExtendedParameters. Methods of this class enable reading the information from structured append that is used to combine several QR Code barcode into one. This data can be obtained using the following methods:
- getQRStructuredAppendModeBarCodeIndex - returns the sequence number of the current barcode (starting from 0)
- getQRStructuredAppendModeBarCodesQuantity - returns the number of barcodes in a composite QR Code barcode taht can take values from 2 to 16
- getQRStructuredAppendModeParityData - returns the checksum identifier byte that is usually computed as XOR of all bytes in which UTF16BE characters are encoded in two bytes
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 special method called is2DCompositeComponent. This methods allows enabling or disabling a 2D component in DataBar barcodes.
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 getValue method that allows getting 1D barcode text and the getCheckSum method that returns the result of checksum computation.
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 special method called getCode128DataPortions that returns decoded parts of barcode input information and the encoding mode.
