pi-motion-detection/lib/ImageCompare.js

A software based detection module for the Raspberry Pi camera

'use strict';

const fs = require('fs');
const path = require('path');
const Jimp = require('jimp');
const EventEmitter = require('events');

class ImageCompare extends EventEmitter {
  constructor(capturesDir) {
    super();
    this.capturesDir = capturesDir;
    this.controlFileName = null;
    this.compareFileName = null;
    this.COMPARE_THRESHOLD = 0.1;
    this.COMPARE_PERCENT_DIFF = 0.001;
  }

  start() {
    const self = this;

    fs.watch(self.capturesDir, (event, filename) => {
      if (filename.indexOf('.jpg') > -1 && filename.indexOf('~') === -1) {
        fs.access(path.resolve(self.capturesDir, filename), fs.constants.R_OK, (error) => {
          if (!error) {
            self.controlFileName = self.controlFileName ? self.controlFileName : filename;
            self.compareFileName = self.controlFileName && !self.compareFileName && filename !== self.controlFileName ? filename : null;

            if (self.controlFileName && self.compareFileName) {
              Jimp.read(path.resolve(self.capturesDir, self.controlFileName), (error, controlFile) => {
                if (error) {
                  self.emit('error', error);
                }

                Jimp.read(path.resolve(self.capturesDir, self.compareFileName), (error, compareFile) => {
                  if (error) {
                    self.emit('error', error);
                  }

                  const diff = Jimp.diff(controlFile, compareFile, self.COMPARE_THRESHOLD);
                  const motionDetected = diff.percent > self.COMPARE_PERCENT_DIFF;

                  if (motionDetected) {
                    self.emit('motion');
                  }

                  fs.unlink(path.resolve(self.capturesDir, self.controlFileName), (error) => {
                    if (error) {
                      self.emit('error', error);
                    }

                    if (motionDetected) {
                      self.controlFileName = null;
                      self.compareFileName = null;
                    }
                    else {
                      self.controlFileName = self.compareFileName;
                      self.compareFileName = null;
                    }
                  });
                });
              });
            }
          }
        });
      }
    });
  }
}

module.exports = ImageCompare;