Author: Sunny Allana
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The Invoice Wizard is a desktop application implemented in Python and PyQt5 that allows users to import invoice images, utilize Optical Character Recognition (OCR) to extract relevant information, and export the extracted data into a CSV file.
The application follows the Model-View-Controller (MVC) architectural pattern. The primary class, InvoicingSystem, extends PyQt5's QMainWindow. Here's an overview of the application's components:
The application doesn't explicitly employ a separate model class. Instead, the extracted invoice data is stored in the invoiceData dictionary attribute of the InvoicingSystem class.
The view component handles the graphical user interface (GUI). PyQt5 widgets like QLabel and QPushButton are used to create GUI elements. The main window, created with QMainWindow, contains labels for the heading, imported image, and extracted OCR text. Import and export buttons allow users to import invoice images and export the extracted data, respectively. The imported image is displayed using a QLabel widget, while the extracted OCR text is displayed using another QLabel widget.
The controller manages interactions between the model and view components. The InvoicingSystem class has methods for importing invoices, performing OCR on imported images, extracting relevant information (invoice number, date, and total amount) from OCR text, and exporting the extracted data to a CSV file. The import button's clicked signal is connected to the importInvoice method, allowing users to select an invoice image file via a file dialog. The selected image undergoes OCR for text extraction. The export button's clicked signal is connected to the exportInvoice method, where users select a destination for the exported CSV file via a file dialog. If the required data is available, the extracted information is written to the CSV file.
OCR functionality is implemented using the pytesseract library, a Python wrapper for Google's Tesseract OCR engine. The perform_ocr method accepts the path to an imported image file, opens it using the PIL library, and performs OCR using pytesseract.image_to_string. The extracted OCR text is returned as a string.
Extracted OCR text is processed to retrieve relevant information such as the invoice number, date, and total amount. The extractInvoiceNumber, extractInvoiceDate, and extractTotalAmount methods utilize regular expressions (re) to search for patterns in the OCR text and extract the required information. Extracted information is stored in the invoiceData dictionary for future use.
The import button allows users to select an invoice image file via a file dialog. The selected file is passed to the perform_ocr method to extract the OCR text. The extracted data is then displayed in the GUI. The export button allows users to select a destination for the exported CSV file via a file dialog. If the required data is available, the extracted information is written to the CSV file. Users are prompted to choose whether to append to an existing CSV file or overwrite it.
The main function creates an instance of the InvoicingSystem class and starts the application's event loop using app.exec_(). The QApplication class from PyQt5 is utilized.