szimek/signature_pad

// Interface for point data structure used e.g. in SignaturePad#fromData method
export interface BasicPoint {
  x: number;
  y: number;
  pressure: number;
  time: number;
}

export class Point implements BasicPoint {
  public x: number;
  public y: number;
  public pressure: number;
  public time: number;

  constructor(x: number, y: number, pressure?: number, time?: number) {
    if (isNaN(x) || isNaN(y)) {
      throw new Error(`Point is invalid: (${x}, ${y})`);
    }
    this.x = +x;
    this.y = +y;
    this.pressure = pressure || 0;
    this.time = time || Date.now();
  }

  public distanceTo(start: BasicPoint): number {
    return Math.sqrt(
      Math.pow(this.x - start.x, 2) + Math.pow(this.y - start.y, 2),
    );
  }

  public equals(other: BasicPoint): boolean {
    return (
      this.x === other.x &&
      this.y === other.y &&
      this.pressure === other.pressure &&
      this.time === other.time
    );
  }

  public velocityFrom(start: BasicPoint): number {
    return this.time !== start.time
      ? this.distanceTo(start) / (this.time - start.time)
      : 0;
  }
}