convertToViewportPoint(x, y) {
    const p = [x, y];
    Util.applyTransform(p, this.transform);
    return p;
  }
Converts PDF point to the viewport coordinates. For examples, useful for
converting PDF location into canvas pixel coordinates.
@param {number} x - The x-coordinate.
@param {number} y - The y-coordinate.
@returns {Array} Array containing `x`- and `y`-coordinates of the
  point in the viewport coordinate space.
@see {@link convertToPdfPoint}
@see {@link convertToViewportRectangle}