VietOCR

BESCHREIBUNG

VietOCR ist ein Java GUI-Frontend für die Tesseract OCR-Engine, welches Texterkennung für gängige Bildformate und mehrseitige Bilder anbietet. Eine Nachbearbeitung der Texterkennung um gewöhnliche Fehler die beim OCR-Prozess auftreten können zu beseitigen ist möglich. Dadurch kann die Erkennungsrate erhöht werden. Das Programm kann ebenso von der Konsole aus ausgeführt werden.

Die Batch-Verarbeitung ist jetzt möglich. Das Programm überwacht den Ordner auf neue Bilddateien, verarbeitet sie automatisch in der OCR-Engine und hinterlegt die Daten in einem Ergebnisordner.

Systemvoraussetzungen

Java Runtime Environment 8 or later. On Windows, Microsoft Visual C++ 2022 Redistributable Package is also required.

INSTALLATION

Tesseract Windows executable is bundled with the program. Additional language data packs for Tesseract, whose names start with ISO639-3 codes, should be placed into the tessdata subdirectory.

Bei Linux , ist Tesseract und seine Sprachpaketen in der Graphics (universe) repository. Sie können installiert werden via Synaptic oder durch folgenden Befehl:

sudo apt-get install tesseract-ocr tesseract-ocr-eng tesseract-ocr-vie

The files will be placed in /usr/bin and /usr/share/tesseract-ocr/tessdata, respectively. On the other hand, if Tesseract is built and installed from the source, they will be placed in /usr/local/bin and /usr/local/share/tessdata. You can also let VietOCR know the location of tessdata via the environment variable TESSDATA_PREFIX:

export TESSDATA_PREFIX=/usr/local/share/

For other platforms, please consult Tesseract Wiki page.

VietOCR also provides support for downloading and installing selected language packs via Download Language Data menu item. Depending on the location of the tessdata folder, you may be required to run the program as root or admin to be able to install the downloaded data into the folder if it is inside a system folder, such as in /usr on Linux or C:\Program Files on Windows.

Scanning support on Windows is provided via the Windows Image Acquisition Library v2.0.

In Linux Systemen ist die Installation von SANE-Paketen erforderlich.

sudo apt-get install libsane sane sane-utils libsane-extras xsane

PDF support is possible via PDFBox.

Die Rechtschreibprüfung ist wird mit Hunspell umgesetzt Wörterbücher-Dateien (.aff, .dic) sollten in dem Ordner dict aus dem VietOCR abgelegt werden. user.dic ist eine UTF-8 kodierte Datei die eine Liste von angepassten Wörter beinhaltet, ein Wort pro Zeile.

On Linux, Hunspell and its dictionaries can be installed by Synaptic or apt, as follows:

sudo apt-get install hunspell hunspell-en-us

ANWEISUNGEN

Da Programm starten:

java -jar VietOCR.jar

Note: Bei "out-of-memory"-Exceptions, bitte ocr Script ausführen statt der Jar-Datei.

The Vietnamese language data were generated for Times New Roman, Arial, Verdana, and Courier New fonts. Therefore, the recognition would have better success rate for images having similar font glyphs. OCRing images that have font glyphs look different from the supported fonts generally will require training Tesseract to create another language data pack specifically for those typefaces. Language data for some VNI and TCVN3 (ABC) fonts have also been bundled in latest versions.

Images to be OCRed should be scanned at resolution from at least 200 DPI (dot per inch) to 400 DPI in monochrome (black&white) or grayscale. Scanning at higher resolutions will not necessarily result in better recognition accuracy, which currently can be higher than 97% for Vietnamese, and the next release of Tesseract may improve it even further. Even so, the actual rates still depend greatly on the quality of the scanned image. The typical settings for scanning are 300 DPI and 1 bpp (bit per pixel) black&white or 8 bpp grayscale uncompressed TIFF or PNG format.

The Screenshot Mode offers better recognition rates for low-resolution images, such as screen prints, by rescaling them to 300 DPI.

In addition to the built-in text postprocessing algorithm, you can add your own custom text replacement scheme via a UTF-8-encoded tab-delimited text file named x.DangAmbigs.txt, where x is the ISO639-3 language code. Both plain and Regex text replacements are supported.

You can put init-only and non-init control parameters in tessdata/configs/tess_configs and tess_configvars files, respectively, to modify Tesseract's behaviour.

Some built-in tools are provided to merge several images or PDF files into a single one for convenient OCR operations, or to split a TIFF or PDF file into smaller ones if it contains too many pages, which can cause out-of-memory exceptions.

NACHBEARBEITUNG

The recognition errors can generally be classified into three categories. Many of the errors are related to the letter cases — for example: hOa, nhắC — which can be easily corrected by popular Unicode text editors. Many other errors are a result of the OCR process, such as missing diacritical marks, wrong letters with similar shape, etc. — huu – hưu, mang – marg, h0a – hoa, la – 1a, uhìu - nhìn. These can also be easily fixed by spell checker programs. The built-in Postprocessing function can help correct many of the aforementioned errors.

The last category of errors is the most difficult to detect because they are semantic errors, which means that the words are valid entries in the dictionary but are wrong in the context — e.g., tinh – tình, vân – vấn. These errors require the editor to read though and manually correct them according to the original image.

Das sind die Anweisungen um die ersten Kategorien von OCR-Fehler mit der eingebauten Funktionalität zu beheben:

  1. Group lines. The lines need to be grouped to the paragraph they belong, as being OCRed, each line becomes a separate 1-line paragraph. Use Remove Line Breaks function under Format menu. Note that this operation may not be needed for poems.
  2. Wählen Sie Groß/Kleinschreibung ändern, auch im Menü unterFormat, und wählen Sie Groß- und Kleinschreibung um die meisten Groß- und Kleinbuchstaben Fehler zu korrigieren. Korrigiere und finde die meisten Groß- und Kleinbuchstaben Fehler.
  3. Korrigieren Sie die Rechtschreibung mit der eingebauten Rechtschreibprüfung.

Through the above process, most of common errors can be eliminated. The remaining, semantic errors are few, but it requires a human editor to read though and make necessary edits to make the document like the original scanned document, and error-free if desired.

Bitte stellen Sie Ihre Fragen unter: VietOCR Forum.