README.md

node-opencv

OpenCV bindings for Node.js

Install

You'll need OpenCV 2.3.1 installed.

Then:

    npm install opencv

Or to build the repo:

    node-gyp rebuild

Examples

Face Detection

    cv.readImage("./examples/test.jpg", function(err, im){
      im.detectObject("./data/haarcascade_frontalface_alt.xml", {}, function(err, faces){  
        for (var i=0;i<faces.length; i++){
          var x = faces[i]
          im.ellipse(x.x + x.width/2, x.y + x.height/2, x.width/2, x.height/2);
        }
        im.save('./out.jpg');   
               
      });
    })

API Documentation

Matrix

The matrix is the most useful base datastructure in OpenCV. Things like images are just matrices of pixels.

Creation

    new Matrix(width, height)

Or you can use opencv to read in image files. Supported formats are in the OpenCV docs, but jpgs etc are supported.

    cv.readImage(filename, function(mat){
      ...
    })

    cv.readImage(buffer, function(mat){
      ...
    })

If you need to pipe data into an image, you can use an imagestream:

    var s = new cv.ImageStream()

    s.on('load', function(matrix){ 
      ...
    }) 

    fs.createReadStream('./examples/test.jpg').pipe(s);        

Accessors

    var mat = new cv.Matrix.Eye(4,4); // Create identity matrix

    mat.get(0,0) // 1

    mat.row(0)  // [1,0,0,0]
    mat.col(4)  // [0,0,0,1]

Image Processing

Object Detection

There is a shortcut method for Viola-Jones Haar Cascade object detection. This can be used for face detection etc.

    mat.detectObject(haar_cascade_xml, opts, function(err, matches){})

WIP

This is a WIP. I've never written C++ before so the code may be interesting - if I'm doing stuff wrong please feel free to correct me.