index.js

var express = require('express');
var router = express.Router();

/* GET home page. */
router.get('/', function (req, res, next) {
    res.render('index', { title: 'Bobblehead Generator' });
});

var oxford = require('project-oxford');
var client = new oxford.Client(process.env.OXFORD_API);

var fs = require('fs');
var GIFEncoder = require('gifencoder');
var pngFileStream = require('png-file-stream');

var Jimp = require("jimp");

function cropHeadAndPasteRotated(inputFile, faceRectangle, degrees, outputName) {
    return new Promise (function (resolve, reject) {
        Jimp.read(inputFile).then(function (image) {
            // Face detection only capture sa small portion of the face,
            // so compensate for this by expanding the area appropriately.
            var height = faceRectangle['height'];
            var top = faceRectangle['top'] - height * 0.5;
            height *= 1.6;
            var left = faceRectangle['left'];
            var width = faceRectangle['width'];
            
            // Crop head, scale up slightly, rotate, and paste on original image
            image.crop(left, top, width, height)
            .scale(1.05)
            .rotate(degrees, function(err, rotatedImage) {
                Jimp.read(inputFile).then(function (original) {
                    original.composite(rotatedImage, left - 0.1*width, top - 0.05*height)
                    .write(outputName, function () {
                        resolve([original.bitmap.width, original.bitmap.height]);
                    });
                });
            });
        });
    });
}

router.post('/', function (req, res, next) {
    Promise.resolve(req.file.path)
        .then(function detectFace(image) {
            console.log("TODO: detect face using Oxford API.")
            return client.face.detect({
                path: image,
                analyzesAge: true,
                analyzesGender: true
            });
        })
        .then(function generateBobblePermutations (response) {
            console.log("TODO: generate multiple images with head rotated.")
            var promises = [];
            var degrees = [10, 0, -10];
            
            for (var i = 0; i < degrees.length; i++) {
                var outputName = req.file.path + '-' + i + '.png';
                promises.push(cropHeadAndPasteRotated(req.file.path, response[0].faceRectangle, degrees[i], outputName))
            }
            
            return Promise.all(promises);
        })
        .then(function generateGif (dimensions) {
            console.log('TODO: generate GIF')
            return new Promise(function (resolve, reject) {              
                var encoder = new GIFEncoder(dimensions[0][0], dimensions[0][1]);
                pngFileStream(req.file.path + '-?.png')
                    .pipe(encoder.createWriteStream({ repeat: 0, delay: 500 }))
                    .pipe(fs.createWriteStream(req.file.path + '.gif'))
                    .on('finish', function () {
                        resolve(req.file.path + '.gif');
                    });
            })
            return req.file.path;
        }).then(function displayGif(gifLocation) {
            res.render('index', { title: 'Done!', image: gifLocation })
        });
});

module.exports = router;