For instance, I would like to extract a screenshot or page only containing the summary of the featured article of wikipedia (http://en.wikipedia.org/wiki/Main_Page).

It should not be of the whole page.

  • Why? Without knowledge of the root problem you are trying to solve it's very difficult to advise you and you will only end up with half solutions. – Gerry Jul 10 '12 at 19:29
  • I would like to know when that specific part of the page is changed. – Tyilo Jul 10 '12 at 19:33

Can you be a little more specific? The problem is that the definition of "part of a page" is completely arbitrary, and it will vary from website to website. So any solution that purports to do this will be limited to some finite subset of all websites out there.

Are you looking to not even retrieve the other bits of the page at all (on your client) or are you wanting to retrieve them and then discard them? You could do something like this clientside quite easily. Getting it through a web service somewhere would be equivalent to going through a filtering proxy, and many of the technologies used for filtering proxies (e.g. privoxy) could be used there, but you'd have to write your own code to determine what's relevant and what's not.

There are too many different possible ways to architect a webpage to reliably create something like this that will trim the "chrome" off of any webpage and only show you the content. For every solution you offer me, I could craft a webpage that would make your solution fall down.

Edit: On the other hand, if all you want is to get the article contents on Wikipedia, THAT is very doable. In fact you could probably write a simple filtering proxy or even some local JavaScript that notices the pattern-based structure of any MediaWiki website and cuts out all the chrome. But of course it wouldn't apply to non-MediaWiki sites...

If you want to know why this isn't possible in the general case, then consider this problem: design me a machine that, without any human intervention aside from physically moving the device within reasonable distance, will perfectly prune any tree, of any height or width or species, to an appropriate size. Good luck with that.

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  • I would provide the css-selector or the pixel coordinates of the part of the page. I need it for an article, where a form is embedded into it. I would like to only see the form. I could easily do this myself, but I thought there must be a website that can do this. – Tyilo Jul 10 '12 at 18:40
  • Having a "website" do this for free with no advertisements or signups would be equivalent to providing an open proxy. I can guarantee you that such a site would be heavily abused and slow if indeed it did exist. Client-side I would recommend looking at the code behind e.g. Adblock because it does a lot of the same type of filtering. – allquixotic Jul 10 '12 at 20:05
  • It doesn't need to update the page more than once an hour or so. – Tyilo Jul 10 '12 at 20:12

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