[SIP-devel] I need some tips on how to equailze an indexed image

[Zhang Cheng]

Hi, guys!

    Because I'm unable to locate the bug which causes mogrify() crash, I
decide to write a new set of functions to replace mogrify(). I've
written a function called histeq() to equalize a grayscale image, and
now I want to write some codes to handle with indexed image(color
image), but I don't know how to do that. I read Matlab's source code and
manual of histeq(), but I'm still confused. I know I should convert RGB
colormap to YIQ colormap, and equalize component Y, but I don't know
what should I do to adjust I and Q. Could you give me some tips or some URL?




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[Angus Errington]

Hi Zhang Cheng,

My understanding: There are many ways to equalize
a colour image. I suspect if you are converting to
YIQ colourspace then you may just want to equalize the
Y (intensity) component. I have also seen equalization
taking place over each R, G and B components.

I suspect Ricardo would know much more about this
than I.

cheers,

Angus



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[Ricardo Fabbri]

I've been  busy,
Sorry guys...

I will invest my time in trying to find that mogrify bug.
It will be a major effort to rewrite mogrify's functions,

good luck anyways, sorry again for not being able to help, but keep it up

On 9/22/05, Angus Errington <aerringt@...> wrote:

> Hi Zhang Cheng,
>
> My understanding: There are many ways to equalize
> a colour image. I suspect if you are converting to
> YIQ colourspace then you may just want to equalize the
> Y (intensity) component. I have also seen equalization
> taking place over each R, G and B components.
>
> I suspect Ricardo would know much more about this
> than I.
>
> cheers,
>
> Angus
>
>
>
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>

--
Ricardo Fabbri

PhD Student in Computer Engineering / Computer Vision
LEMS - Laboratory for Engineering Man-Machine Systems
Brown University, USA


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[Angus Errington]

Hi,

While browsing the scilab contributions website I noticed
a new 'toolbox' in the image tools section--Scilab and
Image Processing Toolbox:

http://sivp.sourceforge.net/

it seems to be quite active and 'new'.


cheers,

Angus


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[Ricardo Fabbri]

Yes,

I contacted the guys and they may merge their project with SIP in the
future. Basically a good feature of their toolbox is the ability to
deal with integer images, and they use Intel's OpenCV as a backend.

Yes, they seem to be quite active recently. We'll have a fruitful
exchange with them (even though they're not working directly together
with us).


On 9/22/05, Angus Errington <aerringt@...> wrote:

> Hi,
>
> While browsing the scilab contributions website I noticed
> a new 'toolbox' in the image tools section--Scilab and
> Image Processing Toolbox:
>
> http://sivp.sourceforge.net/
>
> it seems to be quite active and 'new'.
>
>
> cheers,
>
> Angus
>
>
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> SF.Net email is sponsored by:
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>

--
Ricardo Fabbri

PhD Student in Computer Engineering / Computer Vision
LEMS - Laboratory for Engineering Man-Machine Systems
Brown University, USA


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[Zhang Cheng]

Ricardo Fabbri wrote:

>Yes,
>
>I contacted the guys and they may merge their project with SIP in the
>future. Basically a good feature of their toolbox is the ability to
>deal with integer images, and they use Intel's OpenCV as a backend.
>
>Yes, they seem to be quite active recently. We'll have a fruitful
>exchange with them (even though they're not working directly together
>with us).
>
>
>On 9/22/05, Angus Errington <aerringt@...> wrote:
>  
>
>>Hi,
>>
>>While browsing the scilab contributions website I noticed
>>a new 'toolbox' in the image tools section--Scilab and
>>Image Processing Toolbox:
>>
>>http://sivp.sourceforge.net/
>>
>>it seems to be quite active and 'new'.
>>
>>
>>cheers,
>>
>>Angus
>>
>>
>>-------------------------------------------------------
>>SF.Net email is sponsored by:
>>Tame your development challenges with Apache's Geronimo App Server. Download
>>it for free - -and be entered to win a 42" plasma tv or your very own
>>Sony(tm)PSP.  Click here to play: http://sourceforge.net/geronimo.php
>>_______________________________________________
>>SIPtoolbox-devel mailing list
>>SIPtoolbox-devel@...
>>https://lists.sourceforge.net/lists/listinfo/siptoolbox-devel
>>
>>    
>>
>
>
>--
>Ricardo Fabbri
>
>PhD Student in Computer Engineering / Computer Vision
>LEMS - Laboratory for Engineering Man-Machine Systems
>Brown University, USA
>
>
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>
>  
>

I've understood how to equalize an indexed image after analyzing the
relationship between RGB and YIQ colorspace. And now the equalized
result is as same as that in Matlab. My next step is to write a robust
interface which can equalize the grayscale and indexed images and its
document.
    I've read the source code of equalize function implemented by
ImageMagick. Its method is to equalize the R,G,B channels respectively,
the equalized result in this way contains many extra colors which
degrade the quality of image. I'll report the bug to ImageMagick.

Thank you for your enthusiastic responses!

Zhang Cheng


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