Function toneFromStats

server.js:553–577

(a, b, fps, scope)

}

function toneFromStats(a, b, fps, scope) {
  const brightnessDelta = (a.mean - b.mean) / 255;
  const contrastRatio = Math.max(0.5, Math.min(1.8, a.std / Math.max(1, b.std)));
  const meanPct = ((b.mean - a.mean) / 255) * 100;
  const contrastPct = ((b.std - a.std) / Math.max(1, a.std)) * 100;
  const severity = Math.max(Math.abs(meanPct), Math.abs(contrastPct) * 0.65);
  const recommended = severity >= 1.0;
  const frames = recommended ? Math.max(6, Math.min(18, Math.round(fps * 0.5))) : 0;

  return {
    recommended,
    frames,
    brightnessDelta,
    contrastRatio,
    mean1: a.mean / 255,
    mean2: b.mean / 255,
    contrast1: a.std / 255,
    contrast2: b.std / 255,
    meanDeltaPct: meanPct,
    contrastDeltaPct: contrastPct,
    note: recommended
      ? `${meanPct > 0 ? "brighter" : "darker"} by ${Math.abs(meanPct).toFixed(1)}% with ${Math.abs(contrastPct).toFixed(1)}% contrast shift.`
      : "brightness and contrast are close."
  };
}

function analyzeFrames(video1Frames, video2Frames, fps) {
  const window = Math.min(WINDOW_FRAMES, video1Frames.length, video2Frames.length);