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ocr-preprocessor

This is an asynchronous OCR preprocessor module for NodeJS.

Install

Use npm to install it by running :

npm install --save ocr-preprocessor

Note : This module is only compatible with Linux and OpenCV 2.X

Usage

Require the package

var preprocessor = require("ocr-preprocessor");

Use it on the image you want to process

let options = 
{ 
    blur: 3 , 
    threshold: 255 ,
    matrix: 7 ,
    constant: 5  
};
              
preprocessor("./test.jpg" , "./result.jpg" , options , function(err , path) {
  if (err) {
    console.log("Error !");
  }
  else {
    console.log("Preprocessed Image saved at : " + path);
  }
});

Exports

This module export itself as a single function

This function accept 4 arguments :

Argument	Description	Type
Input Path	Path to the source image	String
Output Path	Path to the destination image	String
Options	Options passed to preprocessing engine	Object
Callback	Callback executed on return	Function

Options

Option	Description	Type	Default
blur	Blur value	Number	0
threshold	Threshold value	Number	255
matrix	Threshold matrix size	Number	3
constant	Threshold constant	Number	5
revert	Revert the image	Boolean	false
isolate	Find and isolate biggest area	Boolean	false
deskew	Run deskew algorithm	Boolean	false
matchCount	Deskew sensibility	Number	100
ratio	Line width threshold for deskew	Number	2
lineStep	Minimum line spacing for deskew	Number	20

Note : ratio is used this way inside of the module :

image.width() / ratio;

Therefore , to select lined that are half the width of the image , ratio should be set to 2.

Asynchronous

This module is asynchronous. All the work is done outside of the node main loop. It allows you to preprocess a big amount of images at the same time.