synopsis-video/utils.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 fs = require('fs');
const cv = require('opencv4nodejs');
const mainDirectory = process.cwd() + '/'
const firstFrameDirectory = mainDirectory + 'firstFrame/'
const rawDirectory = mainDirectory + 'rawSubtractions/'
exports.rawDirectory = rawDirectory
exports.mainDirectory = mainDirectory
exports.firstFrameDirectory = firstFrameDirectory
exports.mergedFramesDirectory = mainDirectory + 'mergedFrames/'
exports.createBaseFolder = (folderName) => {
    try{
        fs.mkdirSync(folderName)
    }catch(err){

    }
}
exports.makeVideoImagesFolder = (folderName) => {
    try{
        fs.mkdirSync(rawDirectory + folderName)
    }catch(err){

    }
}
exports.grabFrames = (videoFile, delay, onFrame, onDone) => {
  const cap = new cv.VideoCapture(videoFile);
  let done = false;
  const intvl = setInterval(() => {
    let frame = cap.read();

    if (frame.empty) {
        done = true
        clearInterval(intvl);
        onDone();
        return
    }
    onFrame(frame);

    const key = cv.waitKey(delay);
    done = key !== -1 && key !== 255;
    if (done) {
      clearInterval(intvl);
      console.log('Key pressed, exiting.');
    }
  }, 0);
};
exports.grabFirstFrame = (videoFile) => {
  const cap = new cv.VideoCapture(videoFile);
  let frame = cap.read();
  // loop back to start on end of stream reached
  if (frame.empty) {
      return null;
  }
  cv.imwrite(`${firstFrameDirectory}${videoFile.split('.')[0]}.jpg`, frame);
};
exports.getMatricesOfContours = (binaryImg, minPxSize, fixedRectWidth, dstImage) => {
  const {
    centroids,
    stats
  } = binaryImg.connectedComponentsWithStats();
  const matrices = [];
  // pretend label 0 is background
  for (let label = 1; label < centroids.rows; label += 1) {
    const [x1, y1] = [stats.at(label, cv.CC_STAT_LEFT), stats.at(label, cv.CC_STAT_TOP)];
    const [x2, y2] = [
      x1 + (fixedRectWidth || stats.at(label, cv.CC_STAT_WIDTH)),
      y1 + (fixedRectWidth || stats.at(label, cv.CC_STAT_HEIGHT))
    ];
    const size = stats.at(label, cv.CC_STAT_AREA);
    const blue = new cv.Vec(255, 0, 0);
    if (minPxSize < size) {
        if(dstImage){
            dstImage.drawRectangle(
              new cv.Point(x1, y1),
              new cv.Point(x2, y2),
              { color: blue, thickness: 2 }
            );
        }else{
            matrices.push([label,x1,y1,x2,y2]);
        }
    }
  }
  return dstImage ? dstImage : matrices
};
exports.stripNameJpg = (name) => {
    return parseInt(name.replace('.jpg',''))
}
exports.stripNamePng = (name) => {
    return parseInt(name.replace('img','').replace('.png',''))
}
exports.splitForFfmpeg = (ffmpegCommandAsString) => {
    //this function ignores spaces inside quotes.
    return ffmpegCommandAsString.replace(/\s+/g,' ').trim().match(/\\?.|^$/g).reduce((p, c) => {
        if(c === '"'){
            p.quote ^= 1;
        }else if(!p.quote && c === ' '){
            p.a.push('');
        }else{
            p.a[p.a.length-1] += c.replace(/\\(.)/,"$1");
        }
        return  p;
    }, {a: ['']}).a
}