fork is not a function

[madc0w]

I've tried with npm installation, with a <script> tag as described, and also by downloading and including the source code in a local library. Same result:

Uncaught TypeError: fork is not a function
    at Object.spawnWorker (http://localhost:3000/packages/modules.js?hash=f54899d92a94c3539fde21055ed0f94e4ddb63b7:26984:14)
    at TesseractWorker._delay (http://localhost:3000/packages/modules.js?hash=f54899d92a94c3539fde21055ed0f94e4ddb63b7:26925:42)
    at TesseractWorker.recognize (http://localhost:3000/packages/modules.js?hash=f54899d92a94c3539fde21055ed0f94e4ddb63b7:26901:15)
    at eval (eval at evaluate (:85:21), <anonymous>:1:11)
    at Object.added (http://localhost:3000/app/app.js?hash=0f20b482913432cbce12028cd756067146dfbc96:11275:8)
    at http://localhost:3000/packages/minimongo.js?hash=66cc6ab213289f154f49d61566dba8ff9dfc33b2:410:13
    at Meteor._SynchronousQueue.runTask (http://localhost:3000/packages/meteor.js?hash=e3f53db3be730057fed1a5f709ecd5fc7cae1229:721:11)
    at Meteor._SynchronousQueue.flush (http://localhost:3000/packages/meteor.js?hash=e3f53db3be730057fed1a5f709ecd5fc7cae1229:749:10)
    at Meteor._SynchronousQueue.drain (http://localhost:3000/packages/meteor.js?hash=e3f53db3be730057fed1a5f709ecd5fc7cae1229:757:12)
    at LocalCollection.insert (http://localhost:3000/packages/minimongo.js?hash=66cc6ab213289f154f49d61566dba8ff9dfc33b2:619:22)

Then I tried installing the fork npm package ( https://www.npmjs.com/package/fork ). This fails, since (I am guessing...) fork is a server-side function. require("fork") on the client results in "Uncaught Error: Cannot find module 'fork'". On the server, I can successfully require fork, but that does not solve this issue, as I was really hoping to use Tesseract client-side.

[madc0w]

Surprisingly, including the <script> tag in a simple HTML file (no Meteor) does actually work. I can only suppose that my attempts to use tesseract.js in Meteor failed due to some mysterious Meteor dependence mangling madness.

Now... we encounter the next issue:

		Tesseract.recognize(canvas).then(function(result) {
			console.log("result " + result);
		});

The "then" function is never executed. I only see this error one time, on load:

pre-main prep time: 111 ms
worker.js:8474 Uncaught DOMException: Failed to execute 'postMessage' on 'DedicatedWorkerGlobalScope': An object could not be cloned.
    at https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8474:16
    at Object.respond (https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8706:9)
    at Object.dispatchHandlers (https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8726:17)
    at https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8473:17

OK, moving on to server-side solutions...

[danrubins]

Hey @madc0w, I was having the same problem with this in Meteor. Once I saw the attempt at using child_process on the client side, I just included the script like you did. Adding a progress handler seems to fix things from that point:

Tesseract.recognize(file)
  .then(function (result) {
    console.log(result)
  }).progress(function (result) {
    console.log(result['status'] + ' (' + (result['progress'] * 100) + '%)')
  })

[antimatter15]

I'm guessing what's happening is that Meteor is ignoring the package.json browser override and trying to load the nodejs server version of the code (which uses child_process.fork). This seems related to this Meteor bug

[madc0w]

@dhrubins , thanks for that hint. After adding the progress handler, I now advance to the next obstacle:

loading tesseract core (0%)
grafix.js:35 loading tesseract core (100%)
grafix.js:35 initializing tesseract (0%)
index.js:10 pre-main prep time: 201 ms
grafix.js:35 initializing tesseract (100%)
worker.js:8474 Uncaught DOMException: Failed to execute 'postMessage' on 'DedicatedWorkerGlobalScope': An object could not be cloned.
    at https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8474:16
    at Object.respond (https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8706:9)
    at Object.dispatchHandlers (https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8726:17)
    at https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/worker.js:8473:17
(anonymous) @ worker.js:8474
respond @ worker.js:8706
dispatchHandlers @ worker.js:8726
(anonymous) @ worker.js:8473

Note that this is with just plain HTML/JS, no Meteor involved here at all.

Anyway, I've long abandoned this client-side OCR approach in favor of using Tesseract on the server, which works fine.

[peonmodel]

dont know if people had figured it out
but i am able to use Tesseractjs client-side with meteor 1.5.1 by importing directly from /dist/

import Tesseract from 'tesseract.js/dist/tesseract.js';

[jeromewu]

Close for now as the issue is resolved.