Question

I help moderate a forum online, and on this forum we restrict the size of signatures. At the moment we test this via a simple Greasemonkey script I wrote; we wrap all signatures with a <div>, the script looks for them, and then measures the div’s height and width.

All the script does right now is make sure the signature resides in a particular height/width. I would like to start measuring the file size of the images inside of a signature automatically so that the script can automatically flag users who are including huge images in their signature. However, I can’t seem to find a way to measure the size of images loaded on the page. I’ve searched and found a property special to IE (element.fileSize) but I obviously can’t use that in my Greasemonkey script.

Is there a way to find out the file size of an image in Firefox via JavaScript?

Edit: People are misinterpreting the problem. The forums themselves do not host images; we host the BBCode that people enter as their signature. So, for example, people enter this:

This is my signature, check out my [url=http://google.com]awesome website[/url]!
This image is cool!  [img]http://image.gif[/img]

I want to be able to check on these images via Greasemonkey. I could write a batch script to scan all of these instead, but I’m just wondering if there’s a way to augment my current script.

Answer 1

Short answer, you cannot

Also, Check on jGuru How can you check the file size from JavaScript in a form with an input type of file?

You will find some important points

Well the answer is very simple, you cannot.

Reason: The browser security does not allow the scripts
(Javascript/VBScript) or even applets and ActiveX Controls to read
files from the local hard disk. You can only read files if your code
is signed by some Certificate Authority (CA). Now the input type
“FILE” also does not have the permission to read files. We cannot do
anything about that since thats what HTML says. So since it cannot
read files, it cannot find the size of the file with which the input
tag is associated. Since it cannot find the file size, there is no
function exposed by JavaScript/VBScript to return the file size. But
if you need to find the file size, say in order to restrict the size
of the file uploaded to your web-server. Then you can do so by
counting the file contents on the server-side, once the user submits
it to the server. Thats what many of the free e-mail providers like
http://www.hotmail.com do.