node-tesseract-ocr

C++ Addon for Node.js, that uses Tesseract OCR (libtesseract-dev) in JavaScript/TypeScript.

Status: WIP

Lizenz: Apache-2.0

Public API

Class: Tesseract

TesseractOptions

 {
    /**
     * Its generally safer to use as few languages as possible.
     * The more languages Tesseract needs to load the longer 
     * it takes to recognize a image.
     * @public
     */
    lang: Array<keyof typeof AvailableLanguages>;

    /**
     * Skip Ocr for when you only want to (for example) analyze the layout
     * @property {boolean} [skipOcr]
     */
    skipOcr?: boolean;

    /**
     * OCR Engine Modes
     * The engine mode cannot be changed after creating the instance
     * If another mode is needed, its advised to create a new instance.
     * @throws {Error} Will throw an error when oem mode is below 0 or over 3
     */
    oemMode?: OcrEngineMode;

    /**
     * Page Segmentation Modes
     * The page segmentation mode cannot be changed after creating the instance
     * If another mode is needed, its advised to create a new instance.
     * @throws {Error} Will throw a error when psm mode is below 0 or over 13
     */
    psm?: PageSegmentationMode;
  }

constructor(options: TesseractOptions)

new Tesseract({
  lang: string,
  skipOcr: boolean
})

recognize

recognize(buffer: Buffer, RecognizeOptions) => Promise<{
  getText() => string;
  getHOCR() => string;
  getTSV() => string;
  getALTO() => string;
}>

Recognize Options

{
  progressChanged?: ({ 
    progress: number; 
    ocrAlive: number;
    top: number; 
    right: number; 
    bottom: number; 
    left: number;
  }) => void,
   
}

Prerequisities

• nodejs
• python3 (for node-gyp)
• node-addon-api
• c++ build-toolchain (e.g. build-essentials)
• libtesseract-dev
• libleptonica-dev
• Tesseract Training-data (eng, deu, ...)

See Install

Install

sudo apt update
sudo apt install -y nodejs npm build-essential python3 pkg-config libtesseract-dev libleptonica-dev tesseract-ocr-eng

git clone [email protected]:luii/node-tesseract-ocr.git
cd node-tesseract-ocr
npm install

Build

npm run build

Start

Either set the NODE_TESSERACT_DATAPATH beforehand or do it in one go, it needs to point to where the training data is located. On a standard install this is usually /usr/share/tesseract-ocr/5/tessdata

NODE_TESSERACT_DATAPATH=/usr/share/tesseract-ocr/5/tessdata npm run dev

Examples

NODE_TESSERACT_DATAPATH=/usr/share/tesseract-ocr/5/tessdata npm run examples:recognize

Special Thanks

• Stunt3000