Embedding images from another SP

[shibboleth655 at lewenberg.com]

We are having an issue related to SAML site A trying to embed images 
from SAML site B.

More details: There are two SAML sites: A and B. Both sites use the same 
IdP but have different entityIDs. The IdP is using single-sign on; that 
is, once a user has authenticated to the IdP, the user does not have to 
enter any more credentials to access sites A or B.

Web pages served from site A use the <img> tag to embed images that come 
from SAML site B. If the user has not authenticated to site B, the links 
from site B embedded in the web page on site A appear as broken images. 
If I click on one of the links, I see the image in its own page. If I 
now go back to the page on site A and reload, all the images now show up.

It appears that by clicking on one of the site B images, I authenticate 
to site B which allows all the other images to load properly once I go 
back to the original web page.

Question: How can I get the images from site B to load on site A's web 
page properly without making the user explicitly visit site B first?