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Dev
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 Posted: Sat Jul 26, 2008 12:34 am Post subject: image without correlation |
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Hi All,
I want to create an image with no or less correlation. I can use a
random value matrix, but I would like to get a histogram similar to a
normal image. For exmple, if I take the 'lena' image, is there a
simple way in Matlab, which I can make this image matrix to a less or
no correlated matrix? Any help is greatly appreciated.
Thanks,
Dev |
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Martin Leese
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| Posted: Sat Jul 26, 2008 7:04 am Post subject: Re: image without correlation |
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Dev wrote:
[quote]Hi All,
I want to create an image with no or less correlation. I can use a
random value matrix, but I would like to get a histogram similar to a
normal image. For exmple, if I take the 'lena' image, is there a
simple way in Matlab, which I can make this image matrix to a less or
no correlated matrix? Any help is greatly appreciated.
[/quote]
Not sure I understand what you want. If you
want an image where the R, G, B channels are
less correlated then you could try the
"Decorrelation Stretch". There are many
links for this including:
http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/docs/ASTER/atbd-ast-06.pdf
However, this will change the channel
histograms, but whatever you do will do
that.
--
Regards,
Martin Leese
E-mail: please@see.Web.for.e-mail.INVALID
Web: http://members.tripod.com/martin_leese/ |
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Marco Al
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| Posted: Sun Jul 27, 2008 6:32 am Post subject: Re: image without correlation |
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Dev wrote:
[quote]I want to create an image with no or less correlation. I can use a
random value matrix, but I would like to get a histogram similar to a
normal image. For exmple, if I take the 'lena' image, is there a
simple way in Matlab, which I can make this image matrix to a less or
no correlated matrix? Any help is greatly appreciated.
[/quote]
Two simple ways immediately evident, generate samples with the same
approximate distribution or perform a random permutation of the original
sequence of pixels.
For the former you simply divide up the range of numbers from 0 to N (N
= number of pixels) in sections with lengths depending on bincounts of
the histogram. Use a white noise rand function with a range from 0 to N
and shade the pixel according to the section the result falls in.
For the second you google for "random permutation".
Regards,
Marco |
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Bob
Guest
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| Posted: Sun Jul 27, 2008 7:32 pm Post subject: Re: image without correlation |
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I think you are confused about correlation. By definition, if the
values of adjacent pixels are correlated, then the power spectrum will
not be flat.
If want the histogram of an image, i.e. the probability density
function of the pixel values, to be flat, then google on histogram
equalization. But this is not the same thing as having adjacent pixel
values uncorrelated. |
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Dev
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| Posted: Mon Jul 28, 2008 3:14 am Post subject: Re: image without correlation |
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On Jul 27, 11:32 am, Marco Al <m.f...@student.utwente.nl> wrote:
[quote]Dev wrote:
I want to create an image with no or less correlation. I can use a
random value matrix, but I would like to get a histogram similar to a
normal image. For exmple, if I take the 'lena' image, is there a
simple way in Matlab, which I can make this image matrix to a less or
no correlated matrix? Any help is greatly appreciated.
Two simple ways immediately evident, generate samples with the same
approximate distribution or perform a random permutation of the original
sequence of pixels.
For the former you simply divide up the range of numbers from 0 to N (N
= number of pixels) in sections with lengths depending on bincounts of
the histogram. Use a white noise rand function with a range from 0 to N
and shade the pixel according to the section the result falls in.
For the second you google for "random permutation".
Regards,
Marco
[/quote]
Hi All,
Thanks for all the replys. I got it working based on Marco>s idea. I
used the block interleaving methods in Matlab (method of algintrlv)
and got the 'lena' image with less correlation and still with the same
histogram.
Thanks again.
Dev |
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