Information regarding formats

[Pedro J CamelloDr Pedro J Camello]

Please, could anybody in the list indicate some online source of
information regarding conversion between graphic types?

My problem is that, to make some measurments, I need to open a series of
bmp images (as a stack) with RGB color format and convert to
grayscale-stack manageable format. I do it but...the new pixel values
are absolutely no sense for me. Even the original RGB values (three
values, of course) are not useful. However, the original application
(Metafluor Analyst) shows the original RGB values as one single value.
Therefore, I think some learning about the maths involved in image
coinversion could help me

Thanks

[Christophe CHAMOT]

Le mardi 13 septembre 2005 à 19:05 +0200, Pedro J Camello a écrit :

> Please, could anybody in the list indicate some online source of
> information regarding conversion between graphic types?
>
> My problem is that, to make some measurments, I need to open a series of
> bmp images (as a stack) with RGB color format and convert to
> grayscale-stack manageable format. I do it but...the new pixel values
> are absolutely no sense for me. Even the original RGB values (three
> values, of course) are not useful. However, the original application
> (Metafluor Analyst) shows the original RGB values as one single value.
> Therefore, I think some learning about the maths involved in image
> coinversion could help me
>
> Thanks

Hello,

If you just do Image > type and check "8-bits" from an RGB image, ImageJ
just calculate the average value in the 3 layers (Red, green and blue).
The greatest value is then 255/3 = 85 for a 1 color image.
In Metafluor, if you have only one value, the software probably
represents your data with a look-up table. Even if it saves in RGB
format.
The quick way to have your values is to separate the RGB layers with
Image > Color > RGB Split. You'll have three separate staks (2 black
ones and the third of your color of interest with values ranging from 0
to 255).

hope it helps ...

--
CHAMOT Christophe
---------------------------------------------------------------------
Plate-Forme de Recherche IFR117
"Imageries des Processus Dynamiques
en Biologie Cellulaire et Biologie du Développement "
Institut Jacques Monod, CNRS, Universités Paris 6 et 7
2, place Jussieu - Tour 43
75251 Paris cedex 05
Tel: [phone]
http://www.ijm.jussieu.fr/
---------------------------------------------------------------------

[Ye Chen]

Where you get your original bmp images?  Your should use your original
application software to save your images as 8 bit color image or called
indexed image. Not save them as RGB image. If you save your images as 8 bit
color (indexed images), your image still shows color but with a look up
table. When you use imageJ to open them and convert to grayscale, the pixel
value won't change, it only discards the look up table. On the other hand,
if you save your images as RGB image, the image doesn't save your original
pixel value, it saves only the color information represented by R,G,B
value. When you use ImageJ to convert RGB image to a grayscale, it just
apply (R+G+B)/3 to each pixel, the pixel value maybe not the same as your
original image pixel value so it may not make sense to you at all.

Hope this will help
Ye Chen

At 01:05 PM 9/13/2005, you wrote:

>Please, could anybody in the list indicate some online source of
>information regarding conversion between graphic types?
>
>My problem is that, to make some measurments, I need to open a series of
>bmp images (as a stack) with RGB color format and convert to
>grayscale-stack manageable format. I do it but...the new pixel values are
>absolutely no sense for me. Even the original RGB values (three values, of
>course) are not useful. However, the original application (Metafluor
>Analyst) shows the original RGB values as one single value. Therefore, I
>think some learning about the maths involved in image coinversion could help me
>
>Thanks