Hi Clara,

If you want to distinguish based on color spectrum, the easiest way is to use the image processing toolbox of MATLAB. You can find an example in the following link:

https://www.mathworks.com/help/images/finding-vegetation-in-a-multispectral-image.html

Hi Clara Clara Morral Martinez

It is so easy

I think It is better to know about pixel & pixel value.

Every image is made from a lot of pixels that have different pixel values.

Also, we have two kinds of photo

1- Gray image

2- Color image

In the standard Grayscale, darker pixels(area) have a lower value (Close to zero) & light pixel has a higher pixel value (in the 8-bit picture close to 256).

Follow these step to determine your particle pixel value:

First of all, You must download ImageJ Fiji from this site :

https://imagej.net/Fiji/Downloads

1- Image --> type --> 8 bit (change your phototype)

2- click on the pixel inspection tool

3- then click on your favorite spot in the image to see the pixel values of the area.

If your pixel values are low, It means they are healthy (because light pixels have lower pixel value).

With best regards

Nima Abbasian thank you very much! very useful and straightforward!!