excalidraw/src/scene/zoom.ts

export const getZoomOrigin = (
  canvas: HTMLCanvasElement | null,
  scale: number,
) => {
  if (canvas === null) {
    return { x: 0, y: 0 };
  }
  const context = canvas.getContext("2d");
  if (context === null) {
    return { x: 0, y: 0 };
  }

  const normalizedCanvasWidth = canvas.width / scale;
  const normalizedCanvasHeight = canvas.height / scale;

  return {
    x: normalizedCanvasWidth / 2,
    y: normalizedCanvasHeight / 2,
  };
};

export const getNormalizedZoom = (zoom: number): number => {
  const normalizedZoom = parseFloat(zoom.toFixed(2));
  const clampedZoom = Math.max(0.1, Math.min(normalizedZoom, 2));
  return clampedZoom;
};