As the name implies, this script simply centers the active layer within the document, both vertically and horizontally.

1. copy the below code in a notepad.
2. For PS CS2 and CS3, save the file with Center Layer 1-0-2.jsx extension. If you are using PS CS then Center Layer 1-0-2.js
3. Copy the file into your "Adobe Photoshop CS#/Presets/Scripts" folder.
4. Restart Photoshop, the script should appear in the File » Scripts menu.


// Author: Trevor Morris (trevor@morris-photographics.com)
// ================================================== ==========================
// Installation:
// 1. Place script in 'C:\Program Files\Adobe\Adobe Photoshop CS2\Presets\Scripts\'
// 2. Restart Photoshop
// 3. Choose File > Scripts > Center Layer
// ================================================== ==========================

// enable double-clicking from Mac Finder or Windows Explorer
#target photoshop // this command only works in Photoshop CS2 and higher

// bring application forward for double-click events
app.bringToFront();

// main function
function centerLayer() {
// ensure that there is at least one document open
if (!documents.length) {
alert('There are no documents open.');
return; // quit
}
// check for background layer, groups, etc.
if (checkInitialConditions()) {
// declare global variables
var docRef = app.activeDocument;
var layerRef = docRef.activeLayer;

// set document resolution to 72ppi (required due to a script bug in Photoshop)
var docRes = activeDocument.resolution;
docRef.resizeImage(undefined, undefined, 72, ResampleMethod.NONE);

var allLocked = activeDocument.activeLayer.allLocked; // remember layer's lock state
var posLocked = activeDocument.activeLayer.positionLocked; // remember layer's lock state

activeDocument.activeLayer.allLocked = false; // unlock layer
activeDocument.activeLayer.positionLocked = false; // unlock layer position

var docWidth = docRef.width;
var docHeight = docRef.height;

// NOTE: both width and height will be off by +2px for shape layers
var layerWidth = layerRef.bounds[2] - layerRef.bounds[0];
var layerHeight = layerRef.bounds[3] - layerRef.bounds[1];

var deltaX = (docWidth - layerWidth)/2 - layerRef.bounds[0];
var deltaY = (docHeight - layerHeight)/2 - layerRef.bounds[1];

layerRef.translate(deltaX, deltaY); // centers the active layer

// restore document's original resolution (required due to a bug)
docRef.resizeImage(undefined, undefined, docRes, ResampleMethod.NONE);

// restore layer's original lock state
layerRef.allLocked = allLocked;
layerRef.positionLocked = posLocked;
}
}

// check background layer, groups, etc.
function checkInitialConditions() {
// check if Background layer is selected
if (activeDocument.activeLayer.isBackgroundLayer) {
alert('The Background layer cannot be centered.\nPlease select another layer and try again.');
return false; // quit
}
// check to see if the current layer contains any artwork
else if (activeDocument.activeLayer.bounds[0] == activeDocument.activeLayer.bounds[2]) {
alert('The current layer contains no artwork.\nPlease select another layer and try again.');
return false; // quit
}
// check to see if a group is currently selected
else if (activeDocument.activeLayer.typename == "LayerSet" && !confirm('Are you sure you want to center the entire group?')) {
return false; // quit
}
// if all above conditions are met, proceed with main function
else {
return true; // continue
}
}

centerLayer();


================================================== ===

__________________
Cheers!!!