Image center

gistfile1.js

const frame = ctx2.getImageData(data.left, data.top, data.width, data.height);
M00 = 0;
M10 = 0;
M01 = 0;
for (var i = 0; i < frame.data.length / 4; i++) {
  const r = frame.data[i * 4];
  const g = frame.data[i * 4 + 1];
  const b = frame.data[i * 4 + 2];
  const intensity = 0.2989*r + 0.5870*g + 0.1140*b;
  const x = i % data.width;
  const y = Math.floor(i / data.width);
  M00 += intensity;
  M10 += x * intensity;
  M01 += y * intensity;
}
const res_x = M10 / M00;
const res_y = M01 / M00;