excalidraw/src/points.ts

import { Point } from "./types";

export const getSizeFromPoints = (points: readonly Point[]) => {
  const xs = points.map((point) => point[0]);
  const ys = points.map((point) => point[1]);
  return {
    width: Math.max(...xs) - Math.min(...xs),
    height: Math.max(...ys) - Math.min(...ys),
  };
};
export const rescalePoints = (
  dimension: 0 | 1,
  nextDimensionSize: number,
  prevPoints: readonly Point[],
): Point[] => {
  const prevDimValues = prevPoints.map((point) => point[dimension]);
  const prevMaxDimension = Math.max(...prevDimValues);
  const prevMinDimension = Math.min(...prevDimValues);
  const prevDimensionSize = prevMaxDimension - prevMinDimension;

  const dimensionScaleFactor =
    prevDimensionSize === 0 ? 1 : nextDimensionSize / prevDimensionSize;

  let nextMinDimension = Infinity;

  const scaledPoints = prevPoints.map(
    (prevPoint) =>
      prevPoint.map((value, currentDimension) => {
        if (currentDimension !== dimension) {
          return value;
        }
        const scaledValue = value * dimensionScaleFactor;
        nextMinDimension = Math.min(scaledValue, nextMinDimension);
        return scaledValue;
      }) as [number, number],
  );

  if (scaledPoints.length === 2) {
    // we don't tranlate two-point lines
    return scaledPoints;
  }

  const translation = prevMinDimension - nextMinDimension;

  const nextPoints = scaledPoints.map(
    (scaledPoint) =>
      scaledPoint.map((value, currentDimension) => {
        return currentDimension === dimension ? value + translation : value;
      }) as [number, number],
  );

  return nextPoints;
};