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PHP Tutorial : PHP & jQuery image upload and crop

Tutorial by:Admin      Date: 2016-04-12 09:01:22

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We needed a PHP and jQuery image upload and crop tool and came up with the following. Hope it helps!

Before you start, ensure you have the following:

  • PHP 4 or Higher (It has been tested on Version 5)
  • Safe mode must be off! – A number of users have reported issues when safe mode is on.
  • PHP GD Library
  • jQuery ver 1.2.3 or Higher
  • Image Area Select plugin by Michal Wojciechowski

Our Requirement

What we needed was a way to upload a JPG image, resize it if required then crop it to given height and width.

  1. Firstly we created a form to allow us to upload an image. Pretty basic, nothing flashy there.

<form action="my_upload.php" enctype="multipart/form-data" method="post">Photo <input name="image" size="30" type="file" /> <input name="upload" type="submit" value="Upload" /></form>

We will be using the session variable to hold the random file name (in our case the timestamp).
We are now also storing the file extension that is passed through the script, to ensure we are dealing with the right type of image.

//only assign a new timestamp if the session variable is empty

    if (strlen($_SESSION['random_key'])==0){

        $_SESSION['random_key'] = strtotime(date('Y-m-d H:i:s')); //assign the timestamp to the session variable

        $_SESSION['user_file_ext']= "";


  1. Capture, rename and resize the uploaded file.

if (isset($_POST["upload"])) {

    //Get the file information

    $userfile_name = $_FILES["image"]["name"];

    $userfile_tmp = $_FILES["image"]["tmp_name"];

    $userfile_size = $_FILES["image"]["size"];

    $filename = basename($_FILES["image"]["name"]);

    $file_ext = substr($filename, strrpos($filename, ".") + 1);


    //Only process if the file is a JPG and below the allowed limit

    if((!empty($_FILES["image"])) && ($_FILES["image"]["error"] == 0)) {

        if (($file_ext!="jpg") && ($userfile_size > $max_file)) {

            $error= "ONLY jpeg images under 1MB are accepted for upload";



        $error= "Select a jpeg image for upload";


    //Everything is ok, so we can upload the image.

    if (strlen($error)==0){


        if (isset($_FILES["image"]["name"])){


            move_uploaded_file($userfile_tmp, $large_image_location);

            chmod ($large_image_location, 0777);


            $width = getWidth($large_image_location);

            $height = getHeight($large_image_location);

            //Scale the image if it is greater than the width set above

            if ($width > $max_width){

                $scale = $max_width/$width;

                $uploaded = resizeImage($large_image_location,$width,$height,$scale);


                $scale = 1;

                $uploaded = resizeImage($large_image_location,$width,$height,$scale);


            //Delete the thumbnail file so the user can create a new one

            if (file_exists($thumb_image_location)) {




        //Refresh the page to show the new uploaded image





The validation section has also been updated and been made more secure by checking the mime type as well as the image extension.

foreach ($allowed_image_types as $mime_type => $ext) {

        //loop through the specified image types and if they match the extension then break out

    //everything is ok so go and check file size

    if($file_ext==$ext && $userfile_type==$mime_type){

        $error = "";



        $error = "Only <strong>".$image_ext."</strong> images accepted for upload";



//check if the file size is above the allowed limit

if ($userfile_size > ($max_file*1048576)) {

    $error.= "Images must be under ".$max_file."MB in size";


  1. Now that the image has been uploaded and saved to our folder we can use the “Image Area Select” plugin to crop our image.

It basically provides the coordinates to the server to handle the crop.

  • x1, y1 = coordinates of the top left corner of the initial selection area
  • x2, y2 = coordinates of the bottom right corner of the initial selection area
  • width = crop selection width
  • height = crop selection height

There are a number of options with this plugin which you can see using the link above. We opted for an aspect ratio of 1:1 (height and width of 100px) along with a preview of what we are actually going to crop.

Lets break it down, we first set the imgAreaSelect function to the image we want to crop, i.e. the one we just uploaded. As you can see, the aspect ration is set to 1:1, which means we are going to get a square selection. The “onSelectChange” is a callback function which runs the preview function when a change is made to the crop.

Update: Using the php calculation below makes the script that much more dynamic, all you now have to do is set the height and width of your thumbnail and the script will calculate the ratio/preview sizes for you!

$(window).load(function () {

    $("#thumbnail").imgAreaSelect({ aspectRatio: "1:thumb_height/thumb_width", onSelectChange: preview });


The preview function below, is run as soon as you create your selection. This places the right part of the image into the preview window. The second part of the function populates hidden fields which are later passed to the server.

function preview(img, selection) {

    var scaleX = 100 / selection.width;

    var scaleY = 100 / selection.height;


    $("#thumbnail + div > img").css({

        width: Math.round(scaleX * 200) + "px",

        height: Math.round(scaleY * 300) + "px",

        marginLeft: "-" + Math.round(scaleX * selection.x1) + "px",

        marginTop: "-" + Math.round(scaleY * selection.y1) + "px"









This function is not really required, but helps by checking to see if the user has made a crop selection. In our case it is a required step. The form is submitted if the values exist, i.e. a selection has been made.

$(document).ready(function () {

    $("#save_thumb").click(function() {

        var x1 = $("#x1").val();

        var y1 = $("#y1").val();

        var x2 = $("#x2").val();

        var y2 = $("#y2").val();

        var w = $("#w").val();

        var h = $("#h").val();

        if(x1=="" || y1=="" || x2=="" || y2=="" || w=="" || h==""){

            alert("You must make a selection first");

            return false;


            return true;




  1. It’s time to handle these new coordinates and generate our new cropped thumbnail.

if (isset($_POST["upload_thumbnail"])) {

    //Get the new coordinates to crop the image.

    $x1 = $_POST["x1"];

    $y1 = $_POST["y1"];

    $x2 = $_POST["x2"]; // not really required

    $y2 = $_POST["y2"]; // not really required

    $w = $_POST["w"];

    $h = $_POST["h"];

    //Scale the image to the 100px by 100px

    $scale = 100/$w;

    $cropped = resizeThumbnailImage($thumb_image_location, $large_image_location,$w,$h,$x1,$y1,$scale);

    //Reload the page again to view the thumbnail





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