CODEWITHSUNDEEP
asp.netjavascriptimagevalidationfile-upload
Gopi
Gopi

Reputation: 5877

Get Image dimensions using Javascript during file upload

I have file upload UI element in which the user will upload images. Here I have to validate the height and width of the image in client side. Is it possible to find the size of the image having only the file path in JS?

Note: If No, is there any other way to find the dimensions in Client side?

Upvotes: 13

Views: 19044

Answers (5)

Gajus
Gajus

Reputation: 73728

The previous example is Okay, but it is far from perfect.

var reader  = new FileReader();

reader.onload   = function(e)
{
    var image   = new Image();

    image.onload    = function()
    {
        console.log(this.width, this.height);
    };

    image.src   = e.target.result;
};

reader.readAsDataURL(this.files[0]);

Upvotes: 9

Guy Thomas
Guy Thomas

Reputation: 1

HTML5 is definitely the correct solution here. You should always code for the future, not the past. The best way to deal with HTML4 browsers is to either fall back on degraded functionality or use Flash (but only if the browser does not support the HTML5 file API)

Using the img.onload event will enable you to recover the dimensions of the file. Its working for an app I'm working on.

Upvotes: 0

Sky Sanders
Sky Sanders

Reputation: 37074

If you use a flash based uploaded such as SWFUpload you can have all the info you want as well as multiple queued uploads.

I recommend SWFUpload and am in no way associated with them other than as a user.

You could also write a silverlight control to pick your file and upload it.

Upvotes: 1

T.J. Crowder
T.J. Crowder

Reputation: 1073968

You can do this on browsers that support the new File API from the W3C, using the readAsDataURL function on the FileReader interface and assigning the data URL to the src of an img (after which you can read the height and width of the image). Currently Firefox 3.6 supports the File API, and I think Chrome and Safari either already do or are about to.

So your logic during the transitional phase would be something like this:

  1. Detect whether the browser supports the File API (which is easy: if (typeof window.FileReader === 'function')).

  2. If it does, great, read the data locally and insert it in an image to find the dimensions.

  3. If not, upload the file to the server (probably submitting the form from an iframe to avoid leaving the page), and then poll the server asking how big the image is (or just asking for the uploaded image, if you prefer).

Edit I've been meaning to work up an example of the File API for some time; here's one:

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
<title>Show Image Dimensions Locally</title>
<style type='text/css'>
body {
    font-family: sans-serif;
}
</style>
<script type='text/javascript'>

    function loadImage() {
        var input, file, fr, img;

        if (typeof window.FileReader !== 'function') {
            write("The file API isn't supported on this browser yet.");
            return;
        }

        input = document.getElementById('imgfile');
        if (!input) {
            write("Um, couldn't find the imgfile element.");
        }
        else if (!input.files) {
            write("This browser doesn't seem to support the `files` property of file inputs.");
        }
        else if (!input.files[0]) {
            write("Please select a file before clicking 'Load'");
        }
        else {
            file = input.files[0];
            fr = new FileReader();
            fr.onload = createImage;
            fr.readAsDataURL(file);
        }

        function createImage() {
            img = document.createElement('img');
            img.onload = imageLoaded;
            img.style.display = 'none'; // If you don't want it showing
            img.src = fr.result;
            document.body.appendChild(img);
        }

        function imageLoaded() {
            write(img.width + "x" + img.height);
            // This next bit removes the image, which is obviously optional -- perhaps you want
            // to do something with it!
            img.parentNode.removeChild(img);
            img = undefined;
        }

        function write(msg) {
            var p = document.createElement('p');
            p.innerHTML = msg;
            document.body.appendChild(p);
        }
    }

</script>
</head>
<body>
<form action='#' onsubmit="return false;">
<input type='file' id='imgfile'>
<input type='button' id='btnLoad' value='Load' onclick='loadImage();'>
</form>
</body>
</html>

Works great on Firefox 3.6. I avoided using any library there, so apologies for the attribute (DOM0) style event handlers and such.

Upvotes: 22

YOU
YOU

Reputation: 123791

No, You can't, filename and file content are send to the server in http headerbody, javascript cannot manipulate those fields.

Upvotes: 0

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