_getCoordinates() {
      const { canvas, width, height, left, top } = this;
      const halfWidth = width / 2;
      const halfHeight = height / 2;
      const canvasHeight = canvas.getHeight(); // fabric object
      const canvasWidth = canvas.getWidth(); // fabric object

      return {
        x: [
          -(halfWidth + left), // x0
          -halfWidth, // x1
          halfWidth, // x2
          halfWidth + (canvasWidth - left - width), // x3
        ].map(Math.ceil),
        y: [
          -(halfHeight + top), // y0
          -halfHeight, // y1
          halfHeight, // y2
          halfHeight + (canvasHeight - top - height), // y3
        ].map(Math.ceil),
      };
    }
Get coordinates
@returns {cropzoneCoordinates} - {@link cropzoneCoordinates}
@private