The response format may be either image/gif, image/jpeg or image/png
To make efficient use of browser-side image caching, the Cover Image Resolver uses HTTP redirects. If an image is requested using its well-known URL that contains multiple ISBNs and a valid image is found for one of the ISBNs, the response will be an HTTP redirect to the well-known URL of the single valid ISBN. This ensures that individual images will be cached only once and that the cached copy will be used if possible.
Example – An image URL redirect in action
The following requests an image for a document that has multiple ISBNs:
The Cover Image Resolver determines that there is a valid image for ISBN 9781920898625.
The Cover Image Resolver returns a redirect as follows:
HTTP/1.x 301 Moved Permanently Date: Tue, 10 Nov 2009 02:24:46 GMT Location: http://api.summon.serialssolutions.com/2.0.0/image/isbn/US9EP2KS0P/9781920898625/small Content-Length: 0
The browser can then request the permanently redirected URL, which returns the following:
HTTP/1.x 200 OK Content-Type: image/gif Date: Tue, 10 Nov 2009 02:24:46 GMT Content-Length: 7073
The redirect and the image are cached, so that when the next time the full three-ISBN url or the short single-ISBN URL is requested, the image will be pulled the from local browser’s cache.