exif.js

var ExifImage = require('exif').ExifImage;

/*
 * Utility function to convert exif data into something a bit more consumable
 * by a template
 */
var exif = function(staticPath, photo, callback){
  // We don't care about errors in here - we can always return an undefined exif
  photo.exif = undefined;

    try {
    new ExifImage({
      image : staticPath//'resources/photos/Ireland/West Coast/_MG_4174.jpg'
    }, function (error, data) {

      if (error){
        //console.log('[exif.js] error in ' + staticPath + ': ' + JSON.stringify(error));
        photo.exif = false;
        return callback(null, photo);
      }else{
        var exifMap = {};
        var image = data.image,
        exif = data.exif,
        gps = data.gps,
        arrays = image.concat(exif, gps);

        for (var i=0; i<arrays.length; i++){
          var t = arrays[i],
          careAbout = { // what props we're interested in, and what we call them in output, rather than silly exif-ey names
            "Make" : "Make",
            "Model" : "Model",
            "DateTimeOriginal" : "Time",
            "ApertureValue" : "aperture",
            "FocalLength" : "focalLength",
            "ISOSpeedRatings" : "ISO",
            "ExposureTime" : "Shutter Speed",
            "GPSLatitude" : "Lat",
            "GPSLongitude" : "Long",
            "ImageDescription" : "Description"
          };
          if (careAbout.hasOwnProperty(t.tagName)){
            var key = careAbout[t.tagName],
            value = t.value;

            if (key == "Shutter Speed"){
              // Transform shutter speed to a fraction
              value = dec2frac(value);
            }
            if (typeof value=="number"){
              value = Math.round(value*100)/100; // no long decimals
            }
            exifMap[key] = value;
          }
        }
        photo.exif = exifMap;
        return callback(null, photo);
      }
    });
  } catch (error) {
    return callback(null, photo);
  }
}

// source: http://stackoverflow.com/questions/95727/how-to-convert-floats-to-human-readable-fractions
function dec2frac(d) {

  var df = 1;
  var top = 1;
  var bot = 1;

  while (df != d) {
    if (df < d) {
      top += 1;
    }
    else {
      bot += 1;
      top = parseInt(d * bot);
    }
    df = top / bot;
  }
  return top + '/' + bot;
}

module.exports = exif;