code: function() {
          OpenLayers.Tile.prototype.clear.apply(this, arguments);
          var img = this.imgDiv;
          if (img) {
              var tile = this.getTile();
              if (tile.parentNode === this.layer.div) {
                  this.layer.div.removeChild(tile);
              }
              this.setImgSrc();
              if (this.layerAlphaHack === true) {
                  img.style.filter = "";
              }
              OpenLayers.Element.removeClass(img, "olImageLoadError");
          }
          this.canvasContext = null;
      }
docs: Method: clear
  Remove the tile from the DOM, clear it of any image related data so that
  it can be reused in a new location.