Tim, I'm sorry, I only just noticed your comment, because I forgot to subscribe to this bug.
I believe the base file time is modified so that the image cache manager knows that that base image was recently in use. (The "image cache manager" is actually an image garbage collector, IIUC.)
I haven't tried your patch instead of mine yet. I'll aim to do that next week, and will report back here.
Tim, I'm sorry, I only just noticed your comment, because I forgot to subscribe to this bug.
I believe the base file time is modified so that the image cache manager knows that that base image was recently in use. (The "image cache manager" is actually an image garbage collector, IIUC.)
I haven't tried your patch instead of mine yet. I'll aim to do that next week, and will report back here.