Use of YCrCb color space model in ImageJ to differenciate weeds from crops

I am currently working on ImageJ to determine soil coverage by crop and soil coverage by weeds (and to know how much soil in uncovered).

Considering the bibliography (https://reader.elsevier.com/reader/sd/pii/S0168169915003981?token=13A2353A58E0E2E199137E767E2465419ECC172EB36B52A55154FE53FEBD185A10BF0BC96E366CE05F6D0762499547F6&originRegion=eu-west-1&originCreation=20210609090434),
I wanted to use the YCrCb color space model with the Cg components.
I already have download the converter from RGB pictures to YCrCb.
At this point I don’t know how can I go further into my analysis to calculate the area of crops and the area of weeds.

Thank you so much for your help !

B.

PS : this image is one of the image I would like to analyse

Bibliography says : “Cg component can be obtained by matrix trans-formations fromRGBcolor space model. Thus, conversion algo-rithm was simpler and calculation was smaller. The conversionformula is as shown in formula(1) Ghazali et al., 2012.” Tang et al., 2016.
I have a matrice but how can I translate that for image J ?