robots.txt and serving images from a separate domain

I'm trying to find out if a robots.txt file set on domain A will still apply to an image served from domain B, but actually displayed on domain A.

Example:

Somewhere on the page on www.example.com, there is an:

<img src="http://img.example.com/images/myimage.jpg" />`

In www.example.com/robots.txt, it says:

User-agent: *
Disallow: /images/

So when the spider hits www.example.com and sees the image being served from img.example.开发者_如何学Ccom, will it index it?

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robots.txt only applies to the hostname it actually exists on.