Convert Vertical Video to Horizontal

// Script to create centered nulls and parent selected layers
// Adds a null at the center of selected layers, named 'column1',
// 'column2', etc. Each time the script runs, it increments the
// number. Selected layers are parented to the created null.
(function() {
  var comp = app.project.activeItem;
  if (!(comp && comp instanceof CompItem)) {
    alert("Please select a composition.");
    return;
  }
  var selectedLayers = comp.selectedLayers;
  if (selectedLayers.length === 0) {
    alert("Please select at least one layer.");
    return;
  }
  app.beginUndoGroup("Create Centered Null and Parent Layers");

  // Determine the next available 'column' name
  var nullIndex = 1;
  while (comp.layer("column" + nullIndex)) {
    nullIndex++;
  }
  var nullName = "column" + nullIndex;

  // Calculate the center position of selected layers
  var minX = Infinity, maxX = -Infinity;
  var minY = Infinity, maxY = -Infinity;
  for (var i = 0; i < selectedLayers.length; i++) {
    var layer = selectedLayers[i];
    var pos = layer.property("Position").value;
    minX = Math.min(minX, pos[0]);
    maxX = Math.max(maxX, pos[0]);
    minY = Math.min(minY, pos[1]);
    maxY = Math.max(maxY, pos[1]);
  }
  var centerX = (minX + maxX) / 2;
  var centerY = (minY + maxY) / 2;

  // Create null at the center position
  var nullLayer = comp.layers.addNull(comp.duration);
  nullLayer.name = nullName;
  nullLayer.property("Position").setValue([centerX, centerY]);

  // Parent selected layers to the null
  for (var i = 0; i < selectedLayers.length; i++) {
    selectedLayers[i].parent = nullLayer;
  }

  app.endUndoGroup();
})();