"The image requests are client side, no? The client requests the images, then streams the responses to a zip file."
No - the image requests happen on the server, which then concatenates them together in to a zip file which is served to the client. The client never sees the actual image files, just the resulting zip file.
I'd imagine (well, hope anyway) that the ISP proxies that downscale image files do so based on the HTTP Content-Type header - since the images contained within a zip file would be part of a file with a different Content-Type they should be left alone.
OK, if the server is the one creating the zip file and sending it to the client, then it probably avoids the issue. I was under the impression that the point of all this was to have the client create the zip, not the server.
No - the image requests happen on the server, which then concatenates them together in to a zip file which is served to the client. The client never sees the actual image files, just the resulting zip file.
I'd imagine (well, hope anyway) that the ISP proxies that downscale image files do so based on the HTTP Content-Type header - since the images contained within a zip file would be part of a file with a different Content-Type they should be left alone.