catfacedetector.js

var http = require('follow-redirects').http;
var express = require('express');
var request = require('request');
var url = require('url');
var fs = require('fs');
var Canvas = require('canvas');
var kittydar = require('kittydar');
var sharp = require('sharp');

var app = express();
var server = http.createServer(app);
app.get('*', function(req, res) {
  try{
    var address = req.query.url;
    if(!address){
      res.json({
        'message': 'Example: /?url=http://url-to-image.png',
      });
      return;
    }
    console.log('address is ' + address);

    request({
      method: 'GET',
      url: address,
      encoding: null,
    }, function (error, response, body) {
      if (!error && response.statusCode == 200) {
        var image = new Canvas.Image;
        image.onload = function(){
          console.log('loaded image ' + address, image.width, image.height);
          var canvas = new Canvas(image.width, image.height);
          var ctx = canvas.getContext('2d');
          ctx.drawImage(image, 0, 0, image.width, image.height);
          try{
            var cats = kittydar.detectCats(canvas);
            res.json({
              'result': cats
            });
          }catch(err){
            res.status(500).json({
              'error': ''+err,
            });
          }
          
        };
        image.onerror = function(err, err1){
          console.log(err);
          res.status(500).json({
            'error': ''+err,
            'comment': 'Error when loading the image',
          });
        };
        try{
          var buffer_png = sharp(body).toFormat('png').toBuffer(function(err, outputBuffer) {
            if (err) {
              console.log('Error in sharp library', err);
              res.status(500).json({
                'comment': 'Error in sharp library while opening or converting to png',
                'error': err+''
              });
            }else{
              image.src = outputBuffer;
            }
          });
        }catch(err){
          console.log('Error in sharp library', err);
          res.status(500).json({
            'comment': 'Error in sharp library while opening or converting to png',
            'error': err+''
          });
        }
      }else{
        console.log('Error in fetching document', error);
        res.status(500).json({
          'comment': 'Error when fetching document',
          'error': error+''
        });
      }
    })
  }catch(err){
    console.log('General error somewhere', err);
    res.status(500).json({
      'error': err,
      'comment': 'General exception in outer try-catch',
    });
  }
  
});

server.listen(1234, 'localhost');
server.on('listening', function() {
  console.log('Express server started on port %s at %s', server.address().port, server.address().address);
});

See the comments here: harthur/kittydar#23 (comment)