openalpr
v0.3.4-alpha.2
Published
Open ALPR JavaScript SDK for Multei
Downloads
38
Readme
OpenALPR JavaScript SDK Documentation
openalpr
is a JS way to recognize license plates and vehicles using OpenALPR API.
You can add openalpr
to your Node.js (including Express) and web (including React) projects.
Get started
This quick start is intended for intermediate to advanced developers.
1. Install the openalpr dependency
npm install openalpr
The above command installs openalpr locally on your project.
Explore our Node.js example
cd example
npm start
You will find some outputs on Terminal.
2. Import or require openalpr
// ES6 import
import openALPR from 'openalpr'
// RequireJS import
const openALPR = require('openalpr')
3. Create a configuration
We recommend that you create a separate file for the openalpr
config.
The config
must be an object with the secretKey
property, like this:
Basics
/**
* @type {{secretKey: string}}
*/
const config = {
secretKey: 'sk_123a4bc56d78e901fa2b3c45' // This is a non-functional key just for this example.
}
// ES6 export
export default config
// RequireJS export
module.exports = config
Replace secretKey
by your CarCheck API Credential (get yours on https://cloud.openalpr.com/cloudapi/).
Make config file more secure
The example above showed just how the configuration should be created.
However, ideally, keys should not be stored in repository files.
Therefore, we recommend that you use the environment variables for this.
/**
* @type {{secretKey: string}}
*/
const config = {
secretKey: process.env.OPENALPR_SECRET_KEY
}
// ES6 export
export default config
// RequireJS export
module.exports = config
Trouble with getting env variables?
On development environments or some projects, maybe you'll need to install dotenv dependency to get env values. We recommend version 8.2.0
or higher.
npm install --save --save-exact dotenv
And then, create (or update) your .env
or .env.development
file with this:
OPENALPR_SECRET_KEY=sk_123a4bc56d78e901fa2b3c45
4. Create an instance
After importing (or requiring) openalpr
, you can create an instance with the config
we created before.
ES6 way
import config from './config'
import openALPR from 'openalpr'
const instance = openALPR.create(config)
RequireJS way
const config = require('./config')
const openALPR = require('openalpr')
const instance = openALPR.create(config)
5. Use recognition service
With blob images from browser Files API
Currently, we support direct recognition only of base64 image files.
If you are working with file inputs on HTML forms, you can use toBase64()
and encode these images before.
Promise.then
// ES6 way
import toBase64 from 'openalpr/dist/toBase64'
// RequireJS way
const toBase64 = require('openalpr/dist/toBase64')
function foo() {
const handleResult = result => {
// @todo recognize result
}
const handleError = error => {
console.error(error)
}
toBase64(file).then(handleResult).catch(handleError)
}
With try/catch
// ES6 way
import toBase64 from 'openalpr/dist/toBase64'
// RequireJS way
const toBase64 = require('openalpr/dist/toBase64')
async function foo() {
let result;
try {
const result = await toBase64(file);
// @todo recognize result
}
catch (error) {
console.error(error)
}
}
With base64 strings
Let's suppose that we have some JPEG data encoded with base64:
const imageData = 'data:image/jpeg;base64,ABCDEFGIHJKLMNOPQRSTUVWXY/Z'
You can call recognize
method from openalpr
, which returns a Promise
:
instance.recognize(data)
.then(r => console.log('Response', r))
.catch(e => console.error('Error', e))
})
Successful response
If image base64 data is valid, and your secret key too, you will find a JSON with recognition results, like this:
Response {
uuid: '',
data_type: 'alpr_results',
epoch_time: 1584024229747,
processing_time: {
total: 785.0690000004761,
plates: 63.24161911010742,
vehicles: 71.50000000001455
},
img_height: 683,
img_width: 1024,
results: [
{
plate: 'ABC1234',
confidence: 85.76541900634766,
region_confidence: 0,
vehicle_region: [Object],
region: '',
plate_index: 0,
processing_time_ms: 19.37890625,
candidates: [Array],
coordinates: [Array],
vehicle: [Object],
matches_template: 1,
requested_topn: 10
}
],
credits_monthly_used: 1,
version: 2,
credits_monthly_total: 2000,
error: false,
regions_of_interest: [ { y: 0, x: 0, height: 683, width: 1024 } ],
credit_cost: 1
}
Error responses
Otherwise, you can find errors like Image data is empty or null. Please check recognize() function call
.
Or even:
{
data: {
error_code: 400,
error: 'Unable to base64 decode image_bytes body'
},
status: 400,
headers: {
// ...
}
}
In this case, check your secret key and base64 image content.
Start contributing
Visit our code of conduct.