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Update to Tesseract.js Version 4 (#691)
See #662 for explanation of Tesseract.js Version 4 changes. List below is auto-generated from commits. * Added image preprocessing functions (rotate + save images) * Updated createWorker to be async * Reworked createWorker to be async and throw errors per #654 * Reworked createWorker to be async and throw errors per #654 * Edited detect to return null when detection fails rather than throwing error per #526 * Updated types per #606 and #580 (#663) (#664) * Removed unused files * Added savePDF option to recognize per #488; cleaned up code for linter * Updated download-pdf example for node to use new savePDF option * Added OutputFormats option/interface for setting output * Allowed for Tesseract parameters to be set through recognition options per #665 * Updated docs * Edited loadLanguage to no longer overwrite cache with data from cache per #666 * Added interface for setting 'init only' options per #613 * Wrapped caching in try block per #609 * Fixed unit tests * Updated setImage to resolve memory leak per #678 * Added debug output option per #681 * Fixed bug with saving images per #588 * Updated examples * Updated readme and Tesseract.js-core version
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‎.eslintrc

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"no-console": 0,
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"global-require": 0,
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"camelcase": 0,
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"no-control-regex": 0
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"no-control-regex": 0,
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// Airbnb disallows ForOfStatement based on the bizarre belief that loops are not readable
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// https://github.com/airbnb/javascript/issues/1271
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"no-restricted-syntax": ["error", "ForInStatement", "LabeledStatement", "WithStatement"]
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}
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}

‎README.md

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```javascript
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import { createWorker } from 'tesseract.js';
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const worker = createWorker({
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const worker = await createWorker({
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logger: m => console.log(m)
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});
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(async () => {
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await worker.load();
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await worker.loadLanguage('eng');
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await worker.initialize('eng');
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const { data: { text } } = await worker.recognize('https://tesseract.projectnaptha.com/img/eng_bw.png');
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[Check out the docs](#documentation) for a full explanation of the API.
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## Major changes in v4
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Version 4 includes many new features and bug fixes--see [this issue](https://github.com/naptha/tesseract.js/issues/662) for a full list. Several highlights are below.
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- Added rotation preprocessing options (including auto-rotate) for significantly better accuracy
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- Processed images (rotated, grayscale, binary) can now be retrieved
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- Improved support for parallel processing (schedulers)
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- Breaking changes:
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- `createWorker` is now async
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- `getPDF` function replaced by `pdf` recognize option
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## Major changes in v3
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- Significantly faster performance
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- Runtime reduction of 84% for Browser and 96% for Node.js when recognizing the [example images](./examples/data)

‎docs/api.md

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# API
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- [createWorker()](#create-worker)
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- [Worker.load](#worker-load)
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- [Worker.writeText](#worker-writeText)
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- [Worker.readText](#worker-readText)
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- [Worker.removeFile](#worker-removeFile)
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```javascript
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const { createWorker } = Tesseract;
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const worker = createWorker({
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const worker = await createWorker({
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langPath: '...',
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logger: m => console.log(m),
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});
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A Worker helps you to do the OCR related tasks, it takes few steps to setup Worker before it is fully functional. The full flow is:
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- load
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- FS functions // optional
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- loadLanguauge
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- initialize
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jobId is generated by Tesseract.js, but you can put your own when calling any of the function above.
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<a name="worker-load"></a>
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### Worker.load(jobId): Promise
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Worker.load() loads tesseract.js-core scripts (download from remote if not presented), it makes Web Worker/Child Process ready for next action.
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**Arguments:**
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- `jobId` Please see details above
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**Examples:**
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```javascript
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(async () => {
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await worker.load();
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})();
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```
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<a name="worker-writeText"></a>
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### Worker.writeText(path, text, jobId): Promise
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- `params` an object with key and value of the parameters
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- `jobId` Please see details above
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**Supported Paramters:**
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**Useful Paramters:**
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| name | type | default value | description |
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| --------------------------- | ------ | ----------------- | ------------------------------------------------------------------------------------------------------------------------------- |
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| tessedit\_char\_whitelist | string | '' | setting white list characters makes the result only contains these characters, useful the content in image is limited |
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| preserve\_interword\_spaces | string | '0' | '0' or '1', keeps the space between words |
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| user\_defined\_dpi | string | '' | Define custom dpi, use to fix **Warning: Invalid resolution 0 dpi. Using 70 instead.** |
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| tessjs\_create\_hocr | string | '1' | only 2 values, '0' or '1', when the value is '1', tesseract.js includes hocr in the result |
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| tessjs\_create\_tsv | string | '1' | only 2 values, '0' or '1', when the value is '1', tesseract.js includes tsv in the result |
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| tessjs\_create\_box | string | '0' | only 2 values, '0' or '1', when the value is '1', tesseract.js includes box in the result |
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| tessjs\_create\_unlv | string | '0' | only 2 values, '0' or '1', when the value is '1', tesseract.js includes unlv in the result |
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| tessjs\_create\_osd | string | '0' | only 2 values, '0' or '1', when the value is '1', tesseract.js includes osd in the result |
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This list is incomplete. As Tesseract.js passes parameters to the Tesseract engine, all parameters supported by the underlying version of Tesseract should also be supported by Tesseract.js. (Note that parameters marked as “init only” in Tesseract documentation cannot be set by `setParameters` or `recognize`.)
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**Examples:**
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**Arguments:**
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- `image` see [Image Format](./image-format.md) for more details.
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- `options` a object of customized options
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- `options` an object of customized options
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- `rectangle` an object to specify the regions you want to recognized in the image, should contain top, left, width and height, see example below.
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- `output` an object specifying which output formats to return (by default `text`, `blocks`, `hocr`, and `tsv` are returned)
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- `jobId` Please see details above
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**Output:**
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```javascript
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const { createWorker } = Tesseract;
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(async () => {
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const worker = createWorker();
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await worker.load();
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const worker = await createWorker();
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await worker.loadLanguage('eng');
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await worker.initialize('eng');
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const { data: { text } } = await worker.recognize(image);
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```javascript
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const { createWorker } = Tesseract;
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(async () => {
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const worker = createWorker();
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await worker.load();
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const worker = await createWorker();
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await worker.loadLanguage('eng');
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await worker.initialize('eng');
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const { data: { text } } = await worker.recognize(image, {
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```javascript
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const { createWorker } = Tesseract;
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(async () => {
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const worker = createWorker();
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await worker.load();
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const worker = await createWorker();
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await worker.loadLanguage('eng');
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await worker.initialize('eng');
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const { data } = await worker.detect(image);
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const { createWorker, createScheduler } = Tesseract;
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const scheduler = createScheduler();
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const worker = createWorker();
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const worker = await createWorker();
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scheduler.addWorker(worker);
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```
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‎docs/examples.md

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```javascript
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const { createWorker } = require('tesseract.js');
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const worker = createWorker();
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const worker = await createWorker();
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(async () => {
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await worker.load();
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await worker.loadLanguage('eng');
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await worker.initialize('eng');
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const { data: { text } } = await worker.recognize('https://tesseract.projectnaptha.com/img/eng_bw.png');
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```javascript
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await worker.load();
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await worker.loadLanguage('eng');
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const { data: { text } } = await worker.recognize('https://tesseract.projectnaptha.com/img/eng_bw.png');
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```javascript
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const worker = createWorker();
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await worker.load();
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await worker.loadLanguage('eng+chi_tra');
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await worker.initialize('eng+chi_tra');
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const { data: { text } } = await worker.recognize('https://tesseract.projectnaptha.com/img/eng_bw.png');
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console.log(text);
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await worker.terminate();
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})();
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```
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### with whitelist char (^2.0.0-beta.1)
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### with whitelist char
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```javascript
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const worker = createWorker();
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const worker = await createWorker();
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(async () => {
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await worker.load();
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await worker.loadLanguage('eng');
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await worker.initialize('eng');
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```
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### with different pageseg mode (^2.0.0-beta.1)
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### with different pageseg mode
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Check here for more details of pageseg mode: https://github.com/tesseract-ocr/tesseract/blob/4.0.0/src/ccstruct/publictypes.h#L163
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```javascript
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const worker = createWorker();
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await worker.load();
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await worker.setParameters({
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### with pdf output (^2.0.0-beta.1)
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### with pdf output
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Please check **examples** folder for details.
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const rectangle = { left: 0, top: 0, width: 500, height: 250 };
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const { createWorker, createScheduler } = require('tesseract.js');
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const worker2 = await createWorker();
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### with multiple workers to speed up (^2.0.0-beta.1)
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### with multiple workers to speed up
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const worker2 = await createWorker();
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‎docs/faq.md

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FAQ
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===
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# Project
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## What is the scope of this project?
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Tesseract.js is the JavaScript/Webassembly port of the Tesseract OCR engine. We do not edit the underlying Tesseract recognition engine in any way. Therefore, if you encounter bugs caused by the Tesseract engine you may open an issue here for the purposes of raising awareness to other users, but fixing is outside the scope of this repository.
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If you encounter a Tesseract bug you would like to see fixed you should confirm the behavior is the same in the [main (CLI) version](https://github.com/tesseract-ocr/tesseract) of Tesseract and then open a Git Issue in that repository.
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# Trained Data
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## How does tesseract.js download and keep \*.traineddata?
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The language model is downloaded by `worker.loadLanguage()` and you need to pass the langs to `worker.initialize()`.
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## How can I train my own \*.traineddata?
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For tesseract.js v2, check [TrainingTesseract 4.00](https://tesseract-ocr.github.io/tessdoc/TrainingTesseract-4.00)
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For tesseract.js v1, check [Training Tesseract 3.03–3.05](https://tesseract-ocr.github.io/tessdoc/Training-Tesseract-3.03%E2%80%933.05)
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## How can I get HOCR, TSV, Box, UNLV, OSD?
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Starting from 2.0.0-beta.1, you can get all these information in the final result.
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const worker = createWorker({
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logger: m => console.log(m)
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(async () => {
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tessedit_create_box: '1',
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tessedit_create_unlv: '1',
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tessedit_create_osd: '1',
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});
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const { data: { text, hocr, tsv, box, unlv } } = await worker.recognize('https://tesseract.projectnaptha.com/img/eng_bw.png');
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console.log(text);
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See the documentation from the main [Tesseract project](https://tesseract-ocr.github.io/tessdoc/) for training instructions.
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‎docs/local-installation.md

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const worker = await createWorker({
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workerPath: 'https://unpkg.com/tesseract.js@v2.0.0/dist/worker.min.js',
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langPath: 'https://tessdata.projectnaptha.com/4.0.0',
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A string specifying the location of the tesseract language files, with default value 'https://tessdata.projectnaptha.com/4.0.0'. Language file URLs are calculated according to the formula `langPath + langCode + '.traineddata.gz'`.
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### corePath
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A string specifying the location of the [tesseract.js-core library](https://github.com/naptha/tesseract.js-core), with default value 'https://unpkg.com/tesseract.js-core@v2.0.0/tesseract-core.wasm.js' (fallback to tesseract-core.asm.js when WebAssembly is not available).
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A string specifying the location of the [tesseract.js-core library](https://github.com/naptha/tesseract.js-core), with default value 'https://unpkg.com/tesseract.js-core@v2.0.0/tesseract-core.wasm.js'.
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Another WASM option is 'https://unpkg.com/tesseract.js-core@v2.0.0/tesseract-core.js' which is a script that loads 'https://unpkg.com/tesseract.js-core@v2.0.0/tesseract-core.wasm'. But it fails to fetch at this moment.

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