Re: best way to select a range of colors

[ritagoncalves]

Boa tarde Rodrigo,

Antes de mais, peço desculpa por estar a utlizar este espaço que criou para a sua dúvida para tentar resolver a minha.
Este mês criei uma pasta designada "Colorimetric Parameters" por forma a me esclarecerem algumas dúvidas sobre os parâmetros L*, a* e b*.  Porém, apesar de ter recebido resposta continuo ainda a não entender e, por isso, resolvi arriscar aqui, uma vez que é Português e, pode ser que melhor entenda o que pretendo.

Eu sou Eng. Agrónoma e estou a estudar a coloração de frutos. Os principais objetivos passam por analisar áreas e coloração. Relativamente às áreas penso que não seja muito complexo, porém, na parte da análise da coloração tenho bastantes dúvidas. É possível obter os valores exatos dos parâmetros L*, a* e b*? A escala que aparece é de 0 a 255, mas a correta seria de 0 a 100, por isso, logo aí não consigo entender. Instalei vários plugins, nomeadamente, o Color Space Converter, o Color Transformer e o Convert RGB image to Lab stack e não consigo obter o que pretendo.

Espero que me consiga ajudar nesta questão, fico a aguardar resposta.

Obrigada.

Rita Gonçalves

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[ctrueden]

Hi Rita,

> I'm still not understand and therefore, decided to risk here, since it
> is Portuguese, and it may be that best understands what I want.

It's best to write in English if you want to get help from most people here.

> in the color of the analysis have many doubts. You can obtain the exact
> values of the parameters L *, a * and b *? The scale shown is 0-255,
> but the correct would be 0-100, so right there I can not understand.

Probably the range 0-100 is linearly mapped to 255. You could convert to
32-bit (Image > Type > 32-bit) then divide by 2.55 to adjust the values
that way.

> I installed various plugins in particular the Color Space Converter,
> the Color Transformer and the Convert RGB image to Lab stack and can
> not get what I want.

Another contender is the conversions_between_lab_stack_and_rgb_image plugin
described on the ImageJ Documentation wiki:

http://imagejdocu.tudor.lu/doku.php?id=plugin:color:conversions_between_rgb_color_space_and_lab_color_space:start

Regards,
Curtis

2015-02-23 6:10 GMT-06:00 Rita Goncalves <[hidden email]>:

> Boa tarde Rodrigo,
>
> Antes de mais, peço desculpa por estar a utlizar este espaço que criou
> para a sua dúvida para tentar resolver a minha.
> Este mês criei uma pasta designada "Colorimetric Parameters" por forma a
> me esclarecerem algumas dúvidas sobre os parâmetros L*, a* e b*.  Porém,
> apesar de ter recebido resposta continuo ainda a não entender e, por isso,
> resolvi arriscar aqui, uma vez que é Português e, pode ser que melhor
> entenda o que pretendo.
>
> Eu sou Eng. Agrónoma e estou a estudar a coloração de frutos. Os
> principais objetivos passam por analisar áreas e coloração. Relativamente
> às áreas penso que não seja muito complexo, porém, na parte da análise da
> coloração tenho bastantes dúvidas. É possível obter os valores exatos dos
> parâmetros L*, a* e b*? A escala que aparece é de 0 a 255, mas a correta
> seria de 0 a 100, por isso, logo aí não consigo entender. Instalei vários
> plugins, nomeadamente, o Color Space Converter, o Color Transformer e o
> Convert RGB image to Lab stack e não consigo obter o que pretendo.
>
> Espero que me consiga ajudar nesta questão, fico a aguardar resposta.
>
> Obrigada.
>
> Rita Gonçalves
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
>

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[ritagoncalves]

Good night Curtis,

Thank you for your comment. The reason why I wrote in Portuguese was because I saw the surname of Rodrigo and I thought he was Portuguese, so I tried to speak with him because when two persons speak the same language is easier. However, he cames from Argentina, he speaks Spanish.
 
So, I'm gonna try again, this time, in English. A few days ago, I wrote here, in the mailing list, a message with the title "Colorimetric Parameters" as you can see if you check it, because I have many doubts about how to analyze color parameters.

I am an Agronomic Engineer and I am studying the color of fruits. When I am analyzing an image, I need to know the exact value of L*, a* and b*. However, I don't understand how i can do it because, for instance, 0 < L* < 100, and in the color threshold window, the range varies between 0 and 255. I don't know how to convert the 0-255 scale into the Lab scale. When I use the Color Space Convert it appears three windows but I can't find the exact value.

I'm sorry if this is a basic question but I found ImageJ just a month ago.

Thanks for helping me.

Regards,
Rita

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[Anderson, Charles (DNR)]

Rita,

Try Analyze | Tools | Synchronize Windows.
Then use the Color Space Converter plugin from RGB to LAB white=D75 separate images.
The resulting L* window has values constrained 0-100.
Draw a rectangular region of interest on the L* image.
Analyze | Histogram will give you min, max, mean, mode, sd for the L* image region.
Click on the margin of the a* image.
Analyze | Histogram
Click on the margin of the b* image.
Analyze | Histogram

Beyond that, I don't know what you mean when you say you want to "find the exact value".

Charles

-----Original Message-----
From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of Rita Goncalves
Sent: Monday, February 23, 2015 3:36 PM
To: [hidden email]
Subject: Re: best way to select a range of colors

Good night Curtis,

Thank you for your comment. The reason why I wrote in Portuguese was because I saw the surname of Rodrigo and I thought he was Portuguese, so I tried to speak with him because when two persons speak the same language is easier. However, he cames from Argentina, he speaks Spanish.
 
So, I'm gonna try again, this time, in English. A few days ago, I wrote here, in the mailing list, a message with the title "Colorimetric Parameters" as you can see if you check it, because I have many doubts about how to analyze color parameters.

I am an Agronomic Engineer and I am studying the color of fruits. When I am analyzing an image, I need to know the exact value of L*, a* and b*. However, I don't understand how i can do it because, for instance, 0 < L* < 100, and in the color threshold window, the range varies between 0 and 255. I don't know how to convert the 0-255 scale into the Lab scale. When I use the Color Space Convert it appears three windows but I can't find the exact value.

I'm sorry if this is a basic question but I found ImageJ just a month ago.

Thanks for helping me.

Regards,
Rita

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[ritagoncalves]

Hello Charles,

Thank you very much for your comment.
I think I get it.

Regards,
Rita

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