//=======================================
//#  image split by n
//=======================================
var doc = app.activeDocument;

// Prompt the user for the number of parts
var n = parseInt(prompt("Enter the number of parts to split the image into:", 4));

// Calculate the height of each part
var partHeight = Math.floor(doc.height / n);

// Create a new document with the width of the original image and the height of one part
var newDoc = app.documents.add(doc.width, partHeight, doc.resolution, "Split Image");

// Loop through each part of the image
for (var i = 0; i < n; i++) {
  // Define the source rectangle for the part
  var sourceRect = [
    [0, i * partHeight],
    [doc.width, i * partHeight],
    [doc.width, (i + 1) * partHeight],
    [0, (i + 1) * partHeight]
  ];

  // Activate the source document
  app.activeDocument = doc;
  // Deselect any active selection
  doc.selection.deselect();
  // Create a new selection
  doc.selection.select(sourceRect);
  // Copy the part to the new document
  doc.selection.copy();
  // Activate the new document
  app.activeDocument = newDoc;
  // Paste the part into the new document
  newDoc.paste();
  // Move the selection down by the height of one part
  app.activeDocument = doc;
  doc.selection.translateBoundary(0, partHeight);
}
//=======================================
//#  trim border
//=======================================
app.activeDocument = newDoc;
newDoc.trim(TrimType.TOPLEFT, true, true, true, true);