synopsis-video/mergeFramePairs.js

Create Video Synopsis from provided videos. Frames are extracted from each video provided and backgrounds are subtracted around moving elements and merged into a single video for quick review.

const {
    rawDirectory,
    mergedFramesDirectory,
    firstFrameDirectory,
    stripNamePng,
    createBaseFolder,
} = require('./utils.js');
const fs = require('fs');
const gm = require('gm').subClass({imageMagick: true})

exports.mergeFramePairs = (rawDirectory,videoNames) => {
    const response = {
        startedAt: new Date(),
        videoNames: videoNames,
        numberOfVideos: videoNames.length,
        numberOfFrames: 0,
    }
    return new Promise((resolve,reject) => {
        var backgroundPath = firstFrameDirectory + fs.readdirSync(firstFrameDirectory)[0]
        var videoImages = {}
        var videoImagePairs = []
        videoNames.forEach((videoName) => {
            const videoFolder = rawDirectory + videoName + '/'
            videoImages[videoName] = fs.readdirSync(videoFolder)
            videoImages[videoName].forEach((filename) => {
                const n = stripNamePng(filename)
                if(!videoImagePairs[n])videoImagePairs[n] = []
                videoImagePairs[n].push(videoFolder + filename)
            })
        })
        if(videoImagePairs.length > 0){
            videoImagePairs.forEach(async (pair,n) => {
                var newImage = gm()
                .in('-geometry', '+0+0')
                .in(backgroundPath)
                pair.forEach((imagePath) => {
                    newImage
                    .in('-geometry', '+0+0')
                    .in(imagePath)
                })
                await newImage.flatten()
                .write(`${mergedFramesDirectory}${n}.jpg`, function (err) {
                    ++response.numberOfFrames
                    if (err){console.log(err)};
                    if(n === videoImagePairs.length - 1){
                        response.endedAt = new Date()
                        response.timeSpent = response.endedAt - response.startedAt
                        resolve(response)
                    }
                });
            })
        }else{
            resolve(response)
        }
    })
}