_drawMask(maskCtx) {
      const { mask } = this;
      const maskImg = mask.getElement();
      const { angle, left, scaleX, scaleY, top } = mask;

      maskCtx.save();
      maskCtx.translate(left, top);
      maskCtx.rotate((angle * Math.PI) / 180);
      maskCtx.scale(scaleX, scaleY);
      maskCtx.drawImage(maskImg, -maskImg.width / 2, -maskImg.height / 2);
      maskCtx.restore();
    }
Draw mask image on canvas element
@param {Object} maskCtx - Context of mask canvas
@private