RGB to grayscale image conversion online:
How to convert RGB to grayscale
Gray RGB color code has equal red,green and blue values:
R = G = B
For each image pixel with red, green and blue values of (R,G,B):
R' = G' = B' = (R+G+B) / 3 = 0.333R + 0.333G + 0.333B
This formula can be changed with different weights for each R/G/B value.
R' = G' = B' = 0.2126R + 0.7152G + 0.0722B
Or
R' = G' = B' = 0.299R + 0.587G + 0.114B
Example
Pixel with RGB values of (30,128,255)
The red level R=30.
The green level G=128.
The blue level B=255.
R' = G' = B' = (R+G+B) / 3 = (30+128+255) / 3 = 138
so the pixel will get RGB values of:
(138,138,138)