XYZ tile to WMS

xyzwms.rb

get '/countymap/:z/:x/:y' do
  x = params[:x].to_i
  y = params[:y].to_i
  z = params[:z].to_i
  maxExtent = {
    "left" => -20037508.34,
    "right" => 20037508.34,
    "top" => 20037508.34,
    "bottom" => -20037508.34
  }
  wmsExtent = { };
  b = 78271.516953125 / ( 2 ** (z - 1) );
  wmsExtent["left"] = b * 256 * x + maxExtent["left"]
  wmsExtent["right"] = b * 256 * (x+1) + maxExtent["left"]
  wmsExtent["top"] = b * -256 * y + maxExtent["top"]
  wmsExtent["bottom"] = b * -256 * (y+1) + maxExtent["top"]
  redirect "http://gis.co.bibb.ga.us/ArcGISBibb/rest/services/AG4LG/ParcelPublicAccess/MapServer/export?bbox=" + wmsExtent["left"].to_s + "," + wmsExtent["bottom"].to_s + "," + wmsExtent["right"].to_s + "," + wmsExtent["top"].to_s + "&bboxSR=102113&layers=&layerdefs=&size=256,256&imageSR=&format=png&transparent=false&dpi=&time=&layerTimeOptions=&f=image"
end