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node-red-nodes/utility/exif/94-exif.js

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2014-11-04 16:07:32 +01:00
/**
* Copyright 2014 IBM Corp.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
**/
module.exports = function(RED) {
"use strict";
var ExifImage = require('exif').ExifImage;
function convertDegreesMinutesSecondsToDecimals(degrees, minutes, seconds) {
var result;
result = degrees + (minutes / 60) + (seconds / 3600);
return result;
}
/***
* Extracts GPS location information from Exif data. If enough information is
* provided, convert the Exif data into a pair of single floating point number
* latitude/longitude data pairs. Populates msg.location with these.
* Assumes that the msg object will always have exifData available as msg.exif.
* Assume that the GPS data saved into Exif provides a valid value
*/
function addMsgLocationDataFromExifGPSData(msg) {
if(msg.exif.gps) {
var gpsData = msg.exif.gps; // declaring variable purely to make checks more readable
if(gpsData.GPSAltitude) {
if(!msg.location) {
msg.location = {};
}
msg.location.alt = gpsData.GPSAltitude;
}
if(gpsData.GPSLatitudeRef && gpsData.GPSLatitude && gpsData.GPSLongitudeRef && gpsData.GPSLongitude) { // location can be determined, OK
// The data provided in Exif is in degrees, minutes, seconds, this is to be converted into a single floating point degree
if(gpsData.GPSLatitude.length === 3) { // OK to convert latitude
if(gpsData.GPSLongitude.length === 3) { // OK to convert longitude
var latitude = convertDegreesMinutesSecondsToDecimals(gpsData.GPSLatitude[0], gpsData.GPSLatitude[1], gpsData.GPSLatitude[2]);
latitude = Math.round(latitude * 100000)/100000;
// (N)orth means positive latitude
// (S)outh means negative latitude
// (E)ast means positive longitude
// (W)est means negative longitude
if(gpsData.GPSLatitudeRef.toString() === 'S' || gpsData.GPSLatitudeRef.toString() === 's') {
latitude = latitude * -1;
}
var longitude = convertDegreesMinutesSecondsToDecimals(gpsData.GPSLongitude[0], gpsData.GPSLongitude[1], gpsData.GPSLongitude[2]);
longitude = Math.round(longitude * 100000)/100000;
if(gpsData.GPSLongitudeRef.toString() === 'W' || gpsData.GPSLongitudeRef.toString() === 'w') {
longitude = longitude * -1;
}
if(!msg.location) {
msg.location = {};
}
msg.location.lat = latitude;
msg.location.lon = longitude;
return;
} else {
node.log("Invalid longitude data, no location information has been added to the message.");
}
} else {
node.log("Invalid latitude data, no location information has been added to the message.");
}
} else {
node.log("The location of this image cannot be determined safely so no location information has been added to the message.");
}
} else {
node.log("No location info found in this image.");
}
}
function ExifNode(n) {
RED.nodes.createNode(this,n);
var node = this;
this.on("input", function(msg) {
try {
if(msg.payload) {
var isBuffer = Buffer.isBuffer(msg.payload);
if(isBuffer === true) {
new ExifImage({ image : msg.payload }, function (error, exifData) {
if (error) {
node.error('Failed to extract Exif data from image.');
node.log('Failed to extract Exif data from image. '+ error);
} else {
//msg.payload remains the same buffer
if(exifData) {
msg.exif = exifData;
addMsgLocationDataFromExifGPSData(msg);
} else {
node.warn("The incoming buffer did not contain Exif data, nothing to do. ");
}
}
node.send(msg);
});
} else {
node.error("Invalid payload received, the Exif node cannot proceed, no messages sent.");
return;
}
} else {
node.error("No payload received, the Exif node cannot proceed, no messages sent.");
return;
}
} catch (error) {
node.error("An error occurred while extracting Exif information. Please check the log for details.");
node.log('Error: '+error.message);
return;
}
});
}
RED.nodes.registerType("exif",ExifNode);
}