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Async OCR

Asynchronous REST OCR API


⚠️ This project is only a POC and it is not production ready or maintained ⚠️

Architecture

  • TypeScript + Express
  • Tesseract.js
  • Redis
  • Bull
sequenceDiagram
    actor User
    participant Server
    participant OCRProcessor
    participant RedisQueue
    participant RedisDB

    User ->> Server: Insert text extraction request (in: File)
    activate Server
    Server ->> RedisQueue: Put in Redis Queue
    Server ->> User: Return "requestID"
    deactivate Server
    RedisQueue -->> OCRProcessor: Process Message
    activate OCRProcessor
    OCRProcessor ->> RedisDB: Insert result on Redis DB
    deactivate OCRProcessor

    User ->> Server: Ask for result (in: requestID)
    activate Server
    Server ->> RedisDB: Search result
    RedisDB ->> Server: Get result
    Server ->> User: Return text extraction result
    deactivate Server
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Available endpoint

POST /api/ocr/recognition/file

Insert request for text extraction

GET /api/ocr/recognition/result

Get result of text extraction

GET /api/ocr/recognition/results

Get multiple results of text extractions in bulk

Script

  • start-dev : run locally on development mode
  • start-prod : run locally on production mode
  • test : run test
  • build : build project
  • prod : run in production and load env vars from deployment environment

Docker

  • docker-build : build docker image
  • docker-run-dev : locally run api and redis (without password)

Install and run Redis via Docker

  1. Pull image: docker pull redis

  2. Run with password: "docker run --name redis -d -p 6379:6379 redis redis-server --requirepass 'redispassword'"

  3. Run without password: "docker run --name redis -d -p 6379:6379 redis"

Redis utils command

Redis Cheatsheet

  • Connect to Redis:
    redis-cli
  • Login:
    AUTH [password]
  • Clean all data:
    FLUSHDB and FLUSHALL
  • Get value type:
    TYPE [key]
  • List all keys:
    KEYS *
  • Sorted set count:
    ZCARD bull:recognize_eng:failed
  • Show Sorted set element:
    ZRANGE bull:recognize_eng:failed 0 0
  • Read Hash:
    HGETALL bull:recognize_eng:419

Bull

Bull Reference

Test

  • Run unit test with npm run test.
  • Run specific test case with npm run test -- ${testNamePattern}. (Es: npm run test -- Redis will run only Redis.test.ts)

Loadtest

loadtest -n 20 -c 5 -P '{"url": "https://tesseract.projectnaptha.com/img/eng_bw.png","lang": "eng"}' http://localhost:8080/api/ocr/recognition -T application/json