opencv/examples/contours.js

Node Bindings to OpenCV

var cv = require('../lib/opencv');

var lowThresh = 0;
var highThresh = 100;
var nIters = 2;
var maxArea = 2500;

var GREEN = [0, 255, 0]; // B, G, R
var WHITE = [255, 255, 255]; // B, G, R
var RED   = [0, 0, 255]; // B, G, R

cv.readImage('./files/stuff.png', function(err, im) {
  if (err) throw err;
  var width = im.width();
  var height = im.height();
  if (width < 1 || height < 1) throw new Error('Image has no size');

  var big = new cv.Matrix(height, width);
  var all = new cv.Matrix(height, width);

  im.convertGrayscale();
  var im_canny = im.copy();

  im_canny.canny(lowThresh, highThresh);
  im_canny.dilate(nIters);

  var contours = im_canny.findContours();
  const lineType = 8;
  const maxLevel = 0;
  const thickness = 1;

  for(i = 0; i < contours.size(); i++) {
    if(contours.area(i) > maxArea) {
      var moments = contours.moments(i);
      var cgx = Math.round(moments.m10 / moments.m00);
      var cgy = Math.round(moments.m01 / moments.m00);
      big.drawContour(contours, i, GREEN, thickness, lineType, maxLevel, [0, 0]);
      big.line([cgx - 5, cgy], [cgx + 5, cgy], RED);
      big.line([cgx, cgy - 5], [cgx, cgy + 5], RED);
    }
  }

  all.drawAllContours(contours, WHITE);

  big.save('./tmp/big.png');
  all.save('./tmp/all.png');
  console.log('Image saved to ./tmp/big.png && ./tmp/all.png');
});