Keep only one color with Gimp

From memory, I took the pipette, picked the spot where the red seemed the most "clean," let's say, and I made a layer filled with that, then I played with the layer options (colors, density and all that, I don't remember which one actually, but you'll see quickly) it brought out the red that I mainly wanted, then some adjustments with the color curves to enhance it a bit.

Edith: you're welcome. It's free.
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Sic Transit Gloria Mundi.

And what do you want the rest to become?
otherwise => http://www.commentcamarche.net/forum/affich 6318476 keep areas in color and others in b&w#0
Or if you just want your image to be in certain colors, you can play with the channels... or you can make a layer of the said color and change its options or opacity.

--
Thus passes the glory of the world.

The rest I would like to disappear
In fact, I use software to quantify the number of pixels in an area... however, I only want to count the red pixels present in each well

thank you again!

my photo: [URL=https://imageshack.com/][IMG]http://img77.imageshack.us/img77/8305/img1657gc6.th.jpg[/IMG][/URL]

Well,
it's really twisted what you're asking actually. Without looking at the photo, I would have said to cut it out, but that would take hours.
I have another solution in mind, but since I was testing it, and a picture is worth a thousand words, let me know if this is what you were looking to do:
http://img123.imageshack.us/img123/4912/helprx0.png

(that said, if it counts the white pixels your thing...)

Edith: play a bit with the color curves to fix it at worst.
--
Thus passes the glory of the world.

Hello Burg
With Photoshop 7 you can do this but I don't know if it's what you want
Open the image
>Image
>Adjustment
Color Balance. Set the red slider to maximum, the others to minimum
Oops, I just saw the previous posts, I’m off track
My apologies and have a good evening. transat
Curiosity on CCM is not a flaw but a quality