how can i discover the values of Y,cb,cr on one pixel (picture) with python

edit

The Wikipedia page on Y Cb Cr has many formulas for converting from RGB.

https://en.wikipedia.org/wiki/YCbCr#I...

Is this what you're looking for?

i don't understand how can i write this in python with pixel for exemple x = img[360,792]
print(x) ===> [125 122 100] how can i have the values now of Y , cb , cr of this pixel ?

R = 255 G = 127 B = 0

Y =   16 +  65.738*R/256 + 129.057*G/256 +  25.064*B/256
Cb = 128 -  37.945*R/256 -  74.494*G/256 + 112.439*B/256
Cr = 128 + 112.439*R/256 -  94.154*G/256 -  18.285*B/256

print(Y)
print(Cb)
print(Cr)

thanks my friend but how can program konw the values R G B with this function ?

Try this code:

import cv2
import numpy

frame = cv2.imread('sparks.png')

if frame is None:
    print('Error loading image')
    exit()

rows = frame.shape[0]
cols = frame.shape[1]

for i in range(0, rows):
    for j in range(0, cols):
        R = frame[i, j][2]
        G = frame[i, j][1]
        B = frame[i, j][0]

        Y =   16 +  65.738*R/256 + 129.057*G/256 +  25.064*B/256
        Cb = 128 -  37.945*R/256 -  74.494*G/256 + 112.439*B/256
        Cr = 128 + 112.439*R/256 -  94.154*G/256 -  18.285*B/256

thanks my friend :)

Pas de problème. :D

and cvtcolor with parameter cv.COLOR_BGR2YCrCb?

@LBerger -- Thanks for pointing that out.

problem (error syntax ) : in loop i , j
for i in range(0, rows): for j in range(0, cols): R = frame[i, j][2] G = frame[i, j][1] B = frame[i, j][0]