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Re: CCD saturation [message #63113 is a reply to message #63022]

Mon, 27 October 2008 09:47

JMB
Messages: 13
Registered: January 2008

Junior Member

Hi Wox,

If you haven't solved your problem yet, here are some ideas to help:

- If your streaks are vertical, you can try to search for them in the
columns of your image matrix.

First you need to identify a threshold to separate "active" pixels
from noisy background:
e.g. T1 = mean(image) x 4,

Then look for columns that are corrupted by streaks:
for i=0,Ncols-1 do column[i]=total(img[i,*] gt T1)

You get for each column the number of "active" pixels and if this
number is higher than a specific threshold this column contains a
streak and you can set the pixels of this column equal to zero (or
background value)

The problem is that by doing this you miss now the "good" pixels
from the center of your active spot/star.
A way to retrieve the center of your bright spots without taking
the streak is to use the median function:
e.g. median(img,5) GT T2
where T2 is a threshold on the image brigthness.
You can visualize the result of the median function by typing:
tvscl, median(img,5) GT T2 ; 0 < T2 < 255 for 8 bit images.
Playing around with the size of the median filter and the value of
T2, you may be able to create a mask that filter out the streaks and
let you only the large spots.

If it doesn't seem clear, please ask

Jérôme

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[Message index]

		Re: CCD saturation By: Wox on Sat, 25 October 2008 06:33
		Re: CCD saturation By: Marshall Perrin on Fri, 24 October 2008 15:23
		Re: CCD saturation By: JMB on Mon, 27 October 2008 09:47
		Re: CCD saturation By: pgrigis on Mon, 27 October 2008 06:27

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