There is another option, but it has it's own issue. In brief, rather than using a refreshing image URL, you use a variable and the
image selection heuristics. The problem with this approach is that it's going to cause your image cache in IT to grow. With IT 2.1 (to be released soon) you can clear the cache when size becomes an issue (and it will eventually will).
This approach assumes that your Mac can somehow know when an image updates. Setup looks something like this:
- Create a variable that will be used to select the image, say "dynamic_image".
- Create an image as the base image which is the same size as your standard images. Save it as "dynamic_image+.png" (or similar) in the variables directory discussed in the image selection link above.
- Open your control page editor and place a Variable page element, select as image and select "dynamic_image+.png" from the image list
That should be all you have to do in Indigo. Now the tricky part, because it's quite specific to your setup. When something on your Mac notices that there's a new image, then you would need to do the following:
- Rename the image to "dynamic_image+XXXX.png", where XXXX is a unique identifier that you won't be reusing (at least for a while - see caching problem above).
- Move the file to the variables folder discussed in the image selection link above.
- Change the value of the "dynamic_image" variable to XXXX (whatever unique value you come up with)
The variable change will force IT to get the "dynamic_image+XXXX.png" from the server (because it's an image it's never cached before because XXXX is unique) and display that. As you can see, the image cache will continue to grow (we never automatically empty images used to represent variables or device states because we don't expect them to be dynamic) until you manually delete the cache. This might be OK though if the images aren't that large, it may take a while before it becomes a problem.
So, if you really have a big issue with bandwidth while you're not on your local network, this might be a better approach even though it would mean periodic cleanup. I wouldn't use this approach myself because I'd forget about manually clearing the cache then when my iPhone started having issues it'd take me a long while to figure out what was going on. But that might be a reasonable tradeoff for you.