AJAX image cropper with YUI and PHP

This post will show you how to build an AJAX crop image tool using the image cropper control from YUI library and PHP. If you are unsure of what PHP is, we touch upon it quickly in our Bluehost guide, click here to read more.

The ImageCropper Control from the YUI library gives you an interactive interface for getting the dimensions to crop an image and using these dimensions in PHP, we can do some cropping.

The script we are going to build will

  • allow users to upload an image via AJAX
  • then allow them to select an area for cropping
  • lastly, provide a download link for the cropped image.

There are 3 files we are going to use

  • index.php – will contain the form for image upload as well as the cropping interface
  • upload.php – provides uploading functionality
  • crop.php – provides cropping functionality

From a technical point of view, the flow will be like this :

  1. user uploads jpg image (index.php)
  2. index.php then posts the image asynchronously to upload.php which will do the upload on the server, returning JSON data containing the image file name, its width and its height.
  3. with the JSON data and innerHTML we put the image in our page
  4. initialize the javascript cropping tool
  5. generate a download link (crop.php)

Let’s have a look at index.php

The index.php is our main file where users will be able upload images and then download the cropped ones.

We’ll need the following components from the YUI library :

  • yahoo-dom-event.js – for DOM manipulation and Event handling
  • dragdrop – dependency for the image cropper control
  • element – dependency for the image cropper control
  • resize – dependency for the image cropper control
  • connection – for AJAX requests, in our case for image uploads via AJAX
  • json – for parsing JSON data
  • imagecropper – our most important control

Of course we’ll use Yahoo combo handling and add the js to our page along with the CSS needed for the above controls :

<link rel="stylesheet" type="text/css" href="http://yui.yahooapis.com/2.5.2/build/resize/assets/skins/sam/resize.css" />
<link rel="stylesheet" type="text/css" href="http://yui.yahooapis.com/2.5.2/build/imagecropper/assets/skins/sam/imagecropper.css" />
<!-- js -->
<script type="text/javascript" src="http://yui.yahooapis.com/combo?2.5.2/build/yahoo-dom-event/yahoo-dom-event.js&2.5.2/build/dragdrop/dragdrop-min.js&2.5.2/build/element/element-beta-min.js&2.5.2/build/resize/resize-beta-min.js&2.5.2/build/imagecropper/imagecropper-beta-min.js&2.

Next users must be able to upload images via AJAX, so we add a form to our page:

<form action="upload.php" enctype="multipart/form-data" method="post" name="uploadForm" id="uploadForm">
	Image : <input type="file" name="uploadImage" id="uploadImage" />
	<input type="button" id="uploadButton" value="Upload"/>

We have an onclick event to the upload button to fire the uploading process.

// add listeners
YAHOO.util.Event.on('uploadButton', 'click', uploader.carry);

We’ll also need 2 containers :

  • imageContainer – will contain our uploaded image
  • downloadLink – will contain the download link
<div id="imageContainer"></div>
<div id="downloadLink"></div>

Both containers will be updated via innerHTML afterwards.

AJAX upload

For the AJAX upload, Code Central

has an excellent tutorial which I highly recommend. I took the code sample and modified it a bit to fit my needs. Finally I came up with a nice JSON object called uploader which has one method, carry. The latter just posts form data to a specified URL.

uploader = {
	carry: function(){
		// set form
		YAHOO.util.Connect.setForm('uploadForm', true);
		// upload image
		YAHOO.util.Connect.asyncRequest('POST', 'upload.php', {
			upload: function(o){
				// parse our json data
				var jsonData = YAHOO.lang.JSON.parse(o.responseText);
				// put image in our image container
				YAHOO.util.Dom.get('imageContainer').innerHTML = '<img id="yuiImg" src="' + jsonData.image + '" width="' + jsonData.width + '" height="' + jsonData.height + '" alt="" />';
				// init our photoshop
				// get first cropped image

When upload is complete, we get the JSON data we mentioned earlier on. For e.g :

{"image" : "images/myimage.jpg", "width" : "500", "height" : 400}

With this data and using innerHTML we update our imageContainer div to put our image which will have yuiImg as id :

YAHOO.util.Dom.get('imageContainer').innerHTML = '<img id="yuiImg" src="' + jsonData.image + '" width="' + jsonData.width + '" height="' + jsonData.height + '" alt="" />';

It’s very important to specify the image width and height else the image cropper won’t work.
Next we initialize another JSON object, photoshop which we’ll have a look now.

Our photoshop object

photoshop = {
	image: null,
	crop: null,
	init: function(image){
		// set our image
		photoshop.image = image;
		// our image cropper from the uploaded image					
		photoshop.crop = new YAHOO.widget.ImageCropper('yuiImg');
		photoshop.crop.on('moveEvent', function() {
			// get updated coordinates
	getCroppedImage: function(){
		var coordinates = photoshop.getCoordinates();
		var url = 'crop.php?image=' + photoshop.image + '&cropStartX=' + coordinates.left +'&cropStartY=' + coordinates.top +'&cropWidth=' + coordinates.width +'&cropHeight=' + coordinates.height;
		YAHOO.util.Dom.get('downloadLink').innerHTML = '<a href="' + url + '">download cropped image</a>';		


	getCoordinates: function(){
		return photoshop.crop.getCropCoords();

The init function iniatializes the YUI image cropper from the uploaded image which has yuiImg as id.

photoshop.crop = new YAHOO.widget.ImageCropper('yuiImg');

We also subscribe to the moveEvent for the cropper since we’ll need to update the download link for the cropped image. So whenever the image cropper is moved/resized, we call the getCroppedImage function.

photoshop.crop.on('moveEvent', function() {
	// get updated coordinates

The getCroppedImage function will generate the download link for the cropped image. To do image cropping in PHP we’ll need

  • the image we want to crop
  • the X,Y coordinates
  • height and width of the to be cropped area

Fortunately the YUI cropper utility has a function which will give us what we want, it’s the getCropCoords() method. So, whenever the getCroppedImage function is called, we get the coordinates of the cropped area, build a URL and finally put the download link in our downloadLink container.

// get coordinates
var coordinates = photoshop.getCoordinates();

// build our url
var url = 'crop.php?image=' + photoshop.image + '&cropStartX=' + coordinates.left +'&cropStartY=' + coordinates.top +'&cropWidth=' + coordinates.width +'&cropHeight=' + coordinates.height;

// put download link in our page
YAHOO.util.Dom.get('downloadLink').innerHTML = '<a href="' + url + '">download cropped image</a>';

This is all we need for the index page.


if(!empty($_FILES["uploadImage"])) {
  	// get file name
	$filename = basename($_FILES['uploadImage']['name']);
	// get extension
  	$ext = substr($filename, strrpos($filename, '.') + 1);
  	// check for jpg only
  	if ($ext == "jpg") {
      		// generate unique file name
  		$newName = 'images/'.time().'.'.$ext;
  		// upload files
        	if ((move_uploaded_file($_FILES['uploadImage']['tmp_name'], $newName))) {
        		// get height and width for image uploaded
        		list($width, $height) = getimagesize($newName);
        		// return json data
           		echo '{"image" : "'.$newName.'", "height" : "'.$height.'", "width" : "'.$width.'" }';
        	else {
           		echo '{"error" : "An error occurred while moving the files"}';
  	else {
     		echo '{"error" : "Invalid image format"}';

The upload.php file too is self explanatory, we check for a jpg image only, then generate an unique filename, put it in the images folder and finally build json data which we’ll use for DOM manipulation. Of course the images folder must be writable by the web server.


// get variables
$imgfile = $_GET['image'];
$cropStartX = $_GET['cropStartX'];
$cropStartY = $_GET['cropStartY'];
$cropW = $_GET['cropWidth'];
$cropH = $_GET['cropHeight'];

// Create two images
$origimg = imagecreatefromjpeg($imgfile);
$cropimg = imagecreatetruecolor($cropW,$cropH);

// Get the original size
list($width, $height) = getimagesize($imgfile);

// Crop
imagecopyresized($cropimg, $origimg, 0, 0, $cropStartX, $cropStartY, $width, $height, $width, $height);

// force download nes image
header("Content-type: image/jpeg");
header('Content-Disposition: attachment; filename="'.$imgfile.'"');

// destroy the images

Crop.php allows us to crop our uploaded image. First we get all the variables passed to us via the AJAX request,

// get variables
$imgfile = $_GET['image'];
$cropStartX = $_GET['cropStartX'];
$cropStartY = $_GET['cropStartY'];
$cropW = $_GET['cropWidth'];
$cropH = $_GET['cropHeight'];

Then we create 2 images, the original one and the cropped one, and use the imagecopyresized function to generate the cropped image. We add some header information to tell the world it’s an image and prompt for a save dialog.

Leave a Reply

Your email address will not be published. Required fields are marked *