crop.js

const async = require('async');
var gm = require('gm');
var sprintf = require("sprintf-js").sprintf;

var faces = require('./faces.json');

var bumps = [];
for (var i = 1; i <= 66; i++) {
  bumps.push(i.toString());
}

async.eachSeries(bumps, function getFace(item, callback) {

  if (faces[item] && faces[item][0] && faces[item][0].faceRectangle) {

    var coords = faces[item][0].faceRectangle;
    var img = gm('./images/babybump' + item + '.jpg');
    img.size(function(err, size) {

      var scalingFactor = (coords.width / 150);

      var newWidth = (Math.round(size.width / scalingFactor));

      coords.left = Math.round(coords.left / scalingFactor);
      coords.top = Math.round(coords.top / scalingFactor);
      coords.width = Math.round(coords.width / scalingFactor);
      coords.height = Math.round(coords.height / scalingFactor);

      var offsetX = Math.floor(coords.left - 500);

      if (offsetX < 0) {
        offsetX = '-' + Math.abs(offsetX);
      } else {
        offsetX = '+' + offsetX;
      }

      var offsetY = Math.floor(coords.top - 500);

      if (offsetY < 0) {
        offsetY = '-' + Math.abs(offsetY);
      } else {
        offsetY = '+' + offsetY;
      }

      var extentOptions = offsetX + offsetY;

      img
        .resize(newWidth)
        .background('black')
        .extent(4096, 4096, extentOptions)
        .crop(1100,1700,100,310)
        .write('./tmp/babybump' + sprintf('%02f', item) + '.jpg', function (err) {
          callback();
        });

    });

  } else {

    async.setImmediate(function() {
        callback();
    });

  }

}, function done(){
  console.log('All done!');
});