Write a JavaScript script for Photoshop image batch processing

2020-04-13 English


JavaScript Photoshop Batch Process

I made a JavaScript script to bulk resize image and canvas, then add watermark and save as new image, learnt a lot during this process.


This is a translation of my original article 用JavaScript写一个Photoshop批处理脚本.

Recently I need to add watermarks for a batch of images, I started to wonder if there are some technical methods to speed up this process after manually finished 3 images with Photoshop.

I have used Actions when I had to shoot photos and edit them all by myself. Actions can record and play repeating steps, I can use it to adjust image size and canvas size, or even add watermark image, merge layers and save in new folder.

But Actions has its limitations. This function cannot adjust image size and canvas size according to image shape, and the images that I have to process don't share the same shape, some of them need resizing based on their width, some on their height. If Actions fails at the first step, then there is no need to do the rest of the steps.

So I Googled relevant information to see if it is possible to customize Actions to meet my requirements. The result comes back positive, but there are only a few conditions to use, and they still cannot solve my problem.

Then I saw this post that said you can use Photoshop Scripts to do this, so I did some research on this and found that Photoshop accepts 3 scripting languages: AppleScript, JavaScript and VBScript.

How convenient that I happen to know one of these languages! Among scripts used by everyone, JavaScript is always number one! (Said by myself)

Let's start copying, no, start learning some tricks then.

JavaScript scripts for Photoshop that I found online

I found 3 JavaScript scripts for Photoshop that might be useful on Google.

Batch resizing image size and image canvas


This script can bulk adjust image size and canvas size and do something more and save them in new folder, I can modify it for my use.

PlaceWatermark scripts


This script can add watermark to images and adjust watermark position. I don't need adjusting since my watermark is exactly the same size as canvas size, so I can use this script after deleting some steps.

Merge all visible layers


There is one thing not mentioned in previous scripts--how to merge all layers. One reply in this page talked about how to merge all visible layers, since I will not use any invisible layers, this will do though.

With the 3 scripts above, I can make my own script now.

Modify the scripts to fit my needs

What I want to do with my images is simple, first adjust image size to no more than 1333 x 1000 px and keep the width/height ratio at the same time, then expand canvas to 1600 x 1200 px and add a 1600 x 1200 px watermark to it, merge watermark layer and background layer and save in a new folder, done.

If done by hand, I can finish one image in 30 seconds, but I can speed up the process and set my hands free with scripts, now I will have time for more cat videos on Youtube.

Also please note that the JS code file needs to be saved as .jsx format, you can click File > Scripts > View in Photoshop to select script and run it.

Full scripts is as follows

app.preferences.rulerUnits = Units.PIXELS;
if (app.documents.length > 0) {//If there is file left open
  alert("Please close all open documents before running this script.");
} else {
  // The width and height for output. You may have to change this to make it dynamic.
  var finalWidth = 1600;
  var finalHeight = 1200;
  // Use folder selection dialogs to get the location of the input files
  // and where to save the new output files.
  var sourceFolder = Folder.selectDialog("Please choose the source image folder.", Folder.myDocuments);
  var destFolder = Folder.selectDialog("Please choose the target image folder", sourceFolder);
  var watermarkFile = File.openDialog("Please choose a watermark image file.", "*.png")
  // Consider only some images filetypes.
  var files = sourceFolder.getFiles(/.+\.(?:jpe?g|bmp|png)$/i);
  var numOfFiles = files.length;
  //Iterate through folder
  for (var i = 0; i < files.length; i++){
    var f = files[i];
    if (f instanceof Folder) {//if file is folder, jump to next
    var docRef = app.open(f);
    var layerRef = docRef.activeLayer;
    //Resize image according to shape
    var actualWidth = docRef.width;
    var actualHeight = docRef.height;
    var imgHeight = 1000;
    var imgWidth = actualWidth * imgHeight / actualHeight;
    if (imgWidth > 1333) {
      imgWidth = 1333;
      imgHeight = actualHeight * imgWidth / actualWidth;
    //Resize canvas, keep img in center
    docRef.resizeCanvas(finalWidth, finalHeight, AnchorPosition.MIDDLECENTER);
    //Add watermark
    var logoFile = watermarkFile; 
    //Merge visible layers, there is no mergeAllLayer function
    } catch(e) {}
    //Get filename and extension to use it when saving.
    var fileExtension = getFileExtension(f.name);
    var filename = getFilename(f.name);
    //Create new image and save as JPG
    var outputFile = new File(destFolder.absoluteURI + "/" + filename + "." + fileExtension);
    saveAsJPG(docRef, outputFile, 10);
    //Close active document, this cannot be done w/o merging all layers
  alert(numOfFiles + " files have been processed.");

function getFileExtension(fullFilename) {
  return fullFilename.split('.').pop();
function getFilename(fullFilename) {
  var finalDotPosition = fullFilename.lastIndexOf(".") ;
  if ( finalDotPosition > -1 ) {
    return fullFilename.substr( 0 , finalDotPosition );
  return fullFilename;
function saveAsJPG(docRef, saveFile, jpegQuality) {
  options = new JPEGSaveOptions();
  options.quality = jpegQuality;
  docRef.saveAs(saveFile, options, false,Extension.LOWERCASE);
function placeWatermark(Image){  
  if(!documents.length) {// if no image is open then return
  var fileObj = new File(Image);// the passed file
  if(!fileObj.exists){// If watermark file does not exits tell user 
    alert(fileObj.name  + " does not exist!");// Alert User 
    var doc = app.activeDocument;// set Doc object to active document
    app.displayDialogs = DialogModes.NO;// Dialog off 
    var strtRulerUnits = app.preferences.rulerUnits;// Save Users ruler units 
    var strtTypeUnits = app.preferences.typeUnits;// Save Users Type units 
    app.preferences.rulerUnits = Units.PIXELS;// work with pixels 
    app.preferences.typeUnits = TypeUnits.PIXELS;// work with pixels 
    var layers = app.activeDocument.layers;// get layers
    app.activeDocument.activeLayer = layers[0];// Target Top Layer
    placeFile(fileObj);// Place in file the Watermark png file
  catch(e) { alert(e + ': on line ' + e.line); }// inform user of error
    app.preferences.rulerUnits = strtRulerUnits;// Restore user ruler units  
    app.preferences.typeUnits = strtTypeUnits;// Restore user type units    
function placeFile(placeFile) {  
  var desc21 = new ActionDescriptor();  
  desc21.putPath( charIDToTypeID('null'), new File(placeFile) );  
  desc21.putEnumerated( charIDToTypeID('FTcs'), charIDToTypeID('QCSt'), charIDToTypeID('Qcsa') );  
  var desc22 = new ActionDescriptor();  
  desc22.putUnitDouble( charIDToTypeID('Hrzn'), charIDToTypeID('#Pxl'), 0.000000 );  
  desc22.putUnitDouble( charIDToTypeID('Vrtc'), charIDToTypeID('#Pxl'), 0.000000 );  
  desc21.putObject( charIDToTypeID('Ofst'), charIDToTypeID('Ofst'), desc22 );  
  executeAction( charIDToTypeID('Plc '), desc21, DialogModes.NO );  

Experience from this

I really like this saying(by myself) "JavaScript is always number one" now, so far I can finish most of the tech-related works with JavaScript, this alone is amazing.

But it seems that there are not many learning materials about JavaScript for Photoshop online, I'll have to wait til next time I encounter a problem to learn more then.

Thumb up for JavaScript here!

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