NativeScript OCR

Optical Character Recognition - powered by Tesseract

Installation

tns plugin add nativescript-ocr

Setup

You'll need to add language files to help Tesseract recognizing text in the images you feed it.

Download version 3.04.00 of the tessdata files here and add your required language to the app/tesseract/tessdata/ folder of your app.

Note that if your language(s) has multiple files (like English: there's 9 files matching eng.*), copy all those files to the folder.

iOS

iOS searches for the tessdata folder in app/App_Resources/iOS, but instead of dulicating the folder you can create a symbolic link:

cd app/App_Resources/iOS
ln -s ../../tesseract/tessdata

API

retrieveText

JavaScript

This is just a basic example using the default settings, look at the TypeScript code below for a more elaborate example.

var OCRPlugin = require("nativescript-ocr");
var ocr = new OCRPlugin.OCR();

ocr.retrieveText({
  image: myImage
}).then(
    function (result) {
      console.log("Result: " + result.text);
    },
    function (error) {
      console.log("Error: " + error);
    }
);

TypeScript

This example shows how to use all possible (but optional) options you can pass into retrieveText:

import { OCR, RetrieveTextResult } from "nativescript-ocr";
import { ImageSource } from "image-source";

export Class MyOCRClass {
  private ocr: OCR;
  
  constructor() {
    this.ocr = new OCR();
  }

  doRecognize(): void {
    let img: ImageSource = new ImageSource();

    img.fromFile("~/samples/scanned.png").then((success: boolean) => {
      if (success) {
        this.ocr.retrieveText({
          image: img,
          whitelist: "ABCDEF",     // you can include only certain characters in the result
          blacklist: "0123456789", // .. or you can exclude certain characters from the result
          onProgress: (percentage: number ) => {
            console.log(`Decoding progress: ${percentage}%`);
          }
        }).then(
            (result: RetrieveTextResult) => {
              this.set(HelloWorldModel.BUSY_KEY, false);
              console.log(`Result: ${result.text}`);
            }, (error: string) => {
              console.log(`Error: ${err}`);
            })
      }
    });
  }
}