Show which images are used and which are unused in a website directory

This is a little bit of a strange question.

I've been working on a website and in it's early stages of development it went through some drastic redesigns (several of them in fact) and now the directory is bloated with images and assets which were part of the old designs. Some of these assets were re-used and some were not. The server space of which I'm uploading the website is smaller than the website at the moment and I know once I clear out the old assets that it'll fit on the webspace.

I'm basically wanting some magical tool to filter o开发者_开发知识库ut which images have been used and which have not - so ultimately I can remove the ones that have not been used.

I ask it in this forum because if there isn't a magical tool to do this (I sincerely hope there is), I'll need to write some sort of script (PHP perhaps?) to accomplish this.

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I have never found one, and tend to take the approach of manually removing old images that I can easily tell are no longer needed. And accepting that I will not get them all.

The reverse approach to this is to remove all of the images, and see which ones are needed ( using firebug or suchlike to identify missing images on the pages ).

The problem with an automated tools is that images in css and code may not be picked up. If you set an image in code, from a range of parameters, how can any tool find that?

I hope someone else can come along and prove me wrong....