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.
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- RE: Frame grabber and image analysis Emmanuel Mayssat
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