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Entry  10 Sep 2012, Shaun Mead, Info, MIDAS button to display image 
    Reply  11 Sep 2012, Stefan Ritt, Info, MIDAS button to display image Screen_Shot_2012-09-11_at_14.36.56_.png
Message ID: 836     Entry time: 11 Sep 2012     In reply to: 835
Author: Stefan Ritt 
Topic: Info 
Subject: MIDAS button to display image 
> Hi,
> I've written a python script that reads some data from a file and generates a
> .png image. I want to have a button on my MIDAS status page that:
> - executes the script and waits for it to finish,
> - then displays the image
> How can I do that? I tried using the sequencer to just execute the script every
> 30 seconds, but I can't get it to work, and it would be better to only execute
> the script on demand anyway. 
> I also am having trouble getting image display to work. I have the ODB keys set:
> [local:oven1:S]/Custom>ls
> Temperature Map&                /home/deap/ovendaq/online/index.html
> Images
> [local:oven1:S]/Custom>ls Images/temps.png/           
> Background                      /home/deap/ovendaq/online/temps.png
> And the HTML file is just this:
> <img src="temps.png">
> But the image won't display. It shows a "broken" picture, and when I try to view
> it directly it says: Invalid custom page: Page not found in ODB.
> Any help would be appreciated...
> Thanks
> Shaun

If you use the "custom" image system, you need to use GIF images. mhttpd can dynamically create GIF 
with a background image and overlaid labels, bar graphs etc. But mhttpd just contains a GIF library to do 
in memory, but no PNG library.

Actually I would recommend you not to use a script to create an image, but use the custom image system 
display temperatures. In the attachment you see an page from our experiment which contains a 
background image (the greyish boxes), labels (white temperature boxes), bar graphs (blue level boxes) 
and history pages (left side). This is all dynamically created inside mhttpd using the custom page system 
without any external script. All you have to do is to get the temperatures and levels inside the ODB via the 
slow control system. If you want, I can send you the full code for that page.

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