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2009-08-04
, 03:36
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Posts: 304 |
Thanked: 233 times |
Joined on Jul 2009
@ São Paulo, SP, Brasil
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#62
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That median filter's not what I want; I'm after a temporal filter, i.e. the median of the same pixel in each image, or something combining that and a little (<1px) spatial averaging. By interleaving the images, it's possible to make a spatial filter and downsampling provide temporal filtering.
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2009-08-04
, 04:50
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Posts: 1,028 |
Thanked: 578 times |
Joined on Mar 2009
@ Chicago
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#63
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2009-08-04
, 11:28
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Posts: 1,635 |
Thanked: 1,816 times |
Joined on Apr 2008
@ Manchester, England
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#64
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hi,
just wondering -- is there some magic parameter I can pass that will allow me to control the gain setting on the camera?
I tried this right now. I took 25 pictures in low light using
mplayer tv:// -tv driver=v4l2:width=640:height=480:noaudio -vf mirror,flip -vo png:z=0 -frames 25
The first image is one of them. Notice the noise, and my hand in the background picking up a cookie from the jar (many of the first frames had my moving hand in it).
The second image is an average of all 25 images, calculated inside the N800 itself using Graphics Magick
gm convert *png -average final.png
The third image was created as you said, using the "median filter" principle along all 25 images, by sorting the values and picking up the middle one --- this is theoretically just another way to obtain the mean value, btw. To do this I wrote a small python script using the PIL library and pylab, which I attached here for reference.
Notice how my hand almost disappeared, while we can see its shadow in the case of the conventional averaging. It seems there is also a little more contrast, and in some of the black portions of the image (as between the keyboard and the table) we got a lot less of the blue noise.
I hope I can manage to port this python script to the N800. Are these libraries available there? Or will I have to go C?
The Following User Says Thank You to lcuk For This Useful Post: | ||
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2009-08-04
, 19:32
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Posts: 304 |
Thanked: 233 times |
Joined on Jul 2009
@ São Paulo, SP, Brasil
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#65
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as for general camera tips, in liqbase I obtain the images directly as YUV frames (usually at 15fps).
I then de-saturate the UV (Chroma) portions by half before presenting them to the user.
it is the best compromise I could find because the greyscale Luma portion does not bleed and has high definition, it was just more noticable with the color parts.
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2009-08-06
, 21:00
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Posts: 304 |
Thanked: 233 times |
Joined on Jul 2009
@ São Paulo, SP, Brasil
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#66
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2009-10-25
, 09:10
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Posts: 49 |
Thanked: 102 times |
Joined on Jul 2009
@ 驚く為五郎
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#67
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2010-10-28
, 04:03
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Posts: 276 |
Thanked: 37 times |
Joined on Jun 2009
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#68
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2010-11-20
, 08:18
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Posts: 3,811 |
Thanked: 1,151 times |
Joined on Oct 2007
@ East Lansing, MI
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#69
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2010-12-22
, 03:36
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Posts: 3,811 |
Thanked: 1,151 times |
Joined on Oct 2007
@ East Lansing, MI
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#70
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just wondering -- is there some magic parameter I can pass that will allow me to control the gain setting on the camera?