Opencv4nodejs: Continuous Face Detection Crash

[djipco]

[Thanks for your awesome work on this library.]

I'm using VideoCapture to detect faces in a webcam feed. If I perform detection a single time, it works fine. However, if I try to call my detectFaces() function in a loop (with setInterval), it crashes my host environment (NW.js, similar to Electron).

Do I need to do any sort of cleanup after each round of detection? Here is the code I'm using:

detectFaces() {

  if (!this.vCap) this.vCap = new cv.VideoCapture(0);

  // Grab frame and perform detection
  const frame = this.vCap.read().bgrToGray();
  const faceClassifier = new cv.CascadeClassifier(cv.HAAR_FRONTALFACE_DEFAULT);
  const faceResult = faceClassifier.detectMultiScale(frame);

  if (!faceResult.objects.length) return;

  const sortByNumDetections = result => result.numDetections
    .map((num, idx) => ({ num, idx }))
    .sort(((n0, n1) => n1.num - n0.num))
    .map(({ idx }) => idx);

  // get best result
  const faceRect = faceResult.objects[sortByNumDetections(faceResult)[0]];

  // draw face detection
  const blue = new cv.Vec(255, 0, 0);
  const thickness = 2;
  frame.drawRectangle(
    new cv.Point(faceRect.x, faceRect.y),
    new cv.Point(faceRect.x + faceRect.width, faceRect.y + faceRect.height),
    blue,
    cv.LINE_8,
    thickness
  );

  // create new ImageData from raw mat data
  const imgData = new ImageData(
    new Uint8ClampedArray(frame.cvtColor(cv.COLOR_GRAY2RGBA).getData()),
    frame.cols,
    frame.rows
  );

  // set canvas dimensions
  const canvas = document.getElementById('capture');
  canvas.height = frame.rows;
  canvas.width = frame.cols;

  // set image data
  canvas.getContext('2d').putImageData(imgData, 0, 0);

}

Obviously, this is not optimized code but I just want to get things rolling.

[djipco]

I updated NW.js to the last version and the problem is gone.

[justadudewhohacks]

Oh okay great! Just a side note: I sometimes had trouble with reading frames from a capture via OpenCV. Sometimes it would fail to read a frame or something, leading to an empty Mat, which crashed my program. Simply checking for mat.empty did the trick for me.