react-native-zoom-toolkit/src/commons/utils/pinchTransform.ts

Most complete set of pinch to zoom utilites for React Native

import type { Vector } from '../types';

type PinchOptions = {
  toScale: number;
  fromScale: number;
  origin: Vector<number>;
  delta: Vector<number>;
  offset: Vector<number>;
};

export const pinchTransform = (options: PinchOptions): Vector<number> => {
  'worklet';

  const { toScale, fromScale, delta, origin, offset } = options;

  const fromPinchX = -1 * (origin.x * fromScale - origin.x);
  const fromPinchY = -1 * (origin.y * fromScale - origin.y);
  const toPinchX = -1 * (origin.x * toScale - origin.x);
  const toPinchY = -1 * (origin.y * toScale - origin.y);

  const x = offset.x + toPinchX - fromPinchX + delta.x;
  const y = offset.y + toPinchY - fromPinchY + delta.y;
  return { x, y };
};