Refresh image (image and CameraFeed widget) and nosuffix

Apps & Services HABPanel
1

Hi all
I’d like to show a snapshot from a camera. It is easy to get it using an url like this one:

http://<ip address>/webcapture.jpg?command=snap&channel=1

Unfortunatly my cam wants exactly the parameters showed and doesn’t answer if i add a time parameter in order to avoid the browser cache.

I’ve tried the Image widget but:
If a set 5 sec refresh time leaving unchecked the “no chache busting” parameter the widget tries to refresh the image but (due to the _t added to the url) the camera doesn’t answer.

If I check the “no chache busting” the widget desn’t refresh at all (it ask fot the image at load but then no more calls has done). I’ve cheked the calls using chrome developers tools (network).

The html code generated by habpanel is very different:
without “no chache”:

image
image864×209 16.6 KB

the pink lines are periodically refreshed.

with “no chache”

image
image834×206 15.8 KB

no refresh at all

Is it possibile to have a refresh witout the “_t” parameter ?

Note
Same behavior using the CameraFeed: the original desn’t have the “nosuffix” params but I’ve customized it adding the parameters.

OpenHab Version:
openHAB 2.2.0-1 (Release Build) - Openhabian

Thanks a lot
f

2

Sorry to bother again, maybe that my post is too trivial or obvious, but currently I’m stuck on this problem.
I kindly ask for an hint, maybe just a “hei give a look here…and wake up !”
Thank you very much.

3

There’s no easy solution for this I’m afraid, maybe a custom widget with a Javascript controller which would remove the <img> node then re-insert it, but I’m not even sure. If the URL doesn’t change your browser might cache the image anyway (it depends on the HTTP headers of the response from your camera).

4

Thanks a lot for the hint. I’ll try with javascript.
The response headers are:

Cache-Control: max-age=315360000Server: uc-httpd 1.0.0
Content-type: image/jpeg
Expires: 0
5

Just to complete the analysis, in term of know how: forget the specific problem of my camera, the behaviour of the image (and, due to inheritance, of CameraFeed) that is no refresh if “nosuffix” flag is set, is ok or it should be analyzed deeper ?
Thanks, I’m available if you need more information or test.

6

Yes I think the widget cannot refresh if there’s no change in the URL.
You can also have a look here:

There’s a workaround: use a String item to hold the URL and use a rule to change it, so that you control the refresh from that rule.