How to get the angle of a document page photo in Node.JS

Pre-processing is a very important step when performing optical character recognition on a document. Without it, accuracy can be greatly compromised. Besides binarization (covered in a separate tutorial), the proper angling of your document is crucial to achieve good results. With today’s API, this is a snap, as you will see soon enough.

Let’s install our client to get the ball rolling. This can be done with npm install with the following command.

npm install cloudmersive-ocr-api-client --save

Now preprocessingGetPageAngle can be invoked with this snippet.

var CloudmersiveOcrApiClient = require('cloudmersive-ocr-api-client');
var defaultClient = CloudmersiveOcrApiClient.ApiClient.instance;
// Configure API key authorization: Apikey
var Apikey = defaultClient.authentications['Apikey'];
Apikey.apiKey = 'YOUR API KEY';
// Uncomment the following line to set a prefix for the API key, e.g. "Token" (defaults to null)
//Apikey.apiKeyPrefix = 'Token';
var apiInstance = new CloudmersiveOcrApiClient.PreprocessingApi();
var imageFile = "/path/to/file"; // File | Image file to perform OCR on.  Common file formats such as PNG, JPEG are supported.
var callback = function(error, data, response) {
if (error) {
console.error(error);
} else {
console.log('API called successfully. Returned data: ' + data);
}
};
apiInstance.preprocessingGetPageAngle(imageFile, callback);

That’s it! Our resulting angle will be returned to us, which we can use to rotate our image to be straight. On to the OCR!