void applyStack() {
   // int minKeepH = minHue, maxKeepH = maxHue; //GL not needed?
   // int minKeepS = minSat, maxKeepS = maxSat;
   // int minKeepB = minBri, maxKeepB = maxBri;
   for (int i = 1; i <= numSlices; i++) {
     imp.setSlice(i);
     if (!checkImage()) {
       IJ.beep();
       IJ.showStatus("No Image");
       return;
     }
     //	minHue = minKeepH;
     //	maxHue = maxKeepH;
     //	minSat = minKeepS;
     //	maxSat = maxKeepS;
     //	minBri = minKeepB;
     //	maxBri = maxKeepB;
     apply(imp, ip);
   }
 }