Can I detect image request by HTTP headers?

Well, I would like to know if it's possible to detect by HTTP headers if request comes from <img tag.

I assume that when request is called from <img tag, I'll not have */* header in HTTP_ACCEPT or I'm missing something.

Regards

EDIT: I've tried with fe开发者_JS百科w browser but i can't conclude nothing by HTTP_ACCEPT...

No, sorry - a browser request made for an img tag will be identical to any other GET request - though as you point out, Firefox does give an Accept header specifying that it expects some kind of image but unless all browsers do this it's not very useful.

What's this for? There might be another way to do what you want.