EPICS Controls Argonne National Laboratory

Experimental Physics and
Industrial Control System

1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  <20072008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024  Index 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  <20072008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 
<== Date ==> <== Thread ==>

Subject: RE: Frame grabber and image analysis
From: "Pearson, MR \(Matthew\)" <[email protected]>
To: "Emmanuel Mayssat" <[email protected]>
Cc: [email protected], EPICS Tech-Talk <[email protected]>
Date: Thu, 30 Aug 2007 10:23:52 +0100
Here is a image processing library, for loading/saving images, accessing
pixel values, drawing overlays, etc.

http://cimg.sourceforge.net/

Also,

http://filters.sourceforge.net/

Regarding the beam profile, positions, etc. Its probably easier to write
your own, since then they can be optimised/parameterisable for your own
situation. Software developed elsewhere might not work in the way you
need, and might need tweaking anyway.

But the image processing libraries can be useful to apply filters that
normalise or clean up the image beforehand (for example, to remove noisy
pixels, or camera/lens artefacts).

You also might find you need to make your algorithms (or filters)
flexible enough to cope with camera degradation. For example, to correct
for damage to the camera readout electronics in the form of lines in the
image.

Another example might be dead pixels in the middle of a bright spot -
you might want to set this pixel to be the average of all the
surrounding pixels.

Cheers,
Matthew
DLS



-----Original Message-----
From: Emmanuel Mayssat [mailto:[email protected]] 
Sent: 29 August 2007 20:28
To: Pearson, MR (Matthew)
Cc: EPICS Tech-Talk; [email protected]
Subject: RE: Frame grabber and image analysis

All,

Following up on an old thread, I moved forward with an axis video
server.
I noted that Motion JPEG is the image format that is being used.
To grab a snapshot we can use a program called axmjpeg that can extract
snapshot from a video stream. This script works quite well. Initially I
was afraid that disk write (of snapshot files) would significantly slow
down the snapshot acquisition. But it doesn't appear to be the case (for
10Hz acquisition).
(Note that the axmjpeg program can pipe its output as well (no disk
write), or can directly be integrated in an epics driver (that's the
beauty of having the source code)).

Then I closely looked at the JPEG format.
JPEG is well suited for video IP (for compression reasons), but that the
losses (due to compression also) may impact computer image analysis.

When describing the JPEG compression algorithm:
"The reason for doing this is that you can afford to lose a lot more
information in the chrominance components than you can in the luminance
component: the human eye is not as sensitive to high-frequency chroma
info as it is to high-frequency luminance."
So JPEG is no good for images with high transition in the chrominance
alpha channel. 

Ok, keeping this in mind, I decided to move forward with JPEG.
No I could use my custom library to compute beam profile, position, etc.
But is there a standard package for image analysis I should know about?
Or is everybody doing it there own way?

Regards,
--
Emmanuel


On Tue, 2007-04-10 at 13:48 +0100, Pearson, MR (Matthew) wrote:

> doesn't have a web server, and needs windows software to view the
video.
> There are software projects out there which can capture IP video, but 
> not sure what Linux support exists.


<DIV><FONT size="1" color="gray">This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail.
Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. 
Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message.
Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
</FONT></DIV> 


References:
Frame grabber Emmanuel Mayssat
RE: Frame grabber Pearson, MR (Matthew)
RE: Frame grabber and image analysis Emmanuel Mayssat

Navigate by Date:
Prev: Observatory Sciences recruitment Philip Taylor
Next: Re: Frame grabber and image analysis Maren Purves
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  <20072008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 
Navigate by Thread:
Prev: Re: Frame grabber and image analysis Maren Purves
Next: RE: Frame grabber Elder Matias
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  <20072008  2009  2010  2011  2012  2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023  2024 
ANJ, 10 Nov 2011 Valid HTML 4.01! · Home · News · About · Base · Modules · Extensions · Distributions · Download ·
· Search · EPICS V4 · IRMIS · Talk · Bugs · Documents · Links · Licensing ·