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node-red-nodes/utility/exif/94-exif.js
2016-11-06 20:26:19 +00:00

99 lines
5.1 KiB
JavaScript

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;
}
function ExifNode(n) {
RED.nodes.createNode(this,n);
var node = this;
/***
* 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) {
var gpsData = msg.exif.gps; // declaring variable purely to make checks more readable
if (gpsData.GPSAltitude) {
/* istanbul ignore else */
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; // 5dp is approx 1m resolution...
// (N)orth means positive latitude, (S)outh means negative latitude
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; // 5dp is approx 1m resolution...
// (E)ast means positive longitude, (W)est means negative longitude
if (gpsData.GPSLongitudeRef.toString() === 'W' || gpsData.GPSLongitudeRef.toString() === 'w') {
longitude = longitude * -1;
}
// Create location property if not exists
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.");
}
}
this.on("input", function(msg) {
try {
if (msg.payload) {
if (Buffer.isBuffer(msg.payload)) {
new ExifImage({ image : msg.payload }, function (error, exifData) {
if (error) {
node.log(error.toString());
} else {
//msg.payload remains the same buffer
if ((exifData) && (exifData.hasOwnProperty("gps")) && (Object.keys(exifData.gps).length !== 0)) {
msg.exif = exifData;
addMsgLocationDataFromExifGPSData(msg);
} else {
node.warn("The incoming image did not contain Exif GPS 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);
}