Can you explain more about the mean value for each channel?

[sunnylulu]

Hi,

I have a question about the values(_R_MEAN, _G_MEAN, _B_MEAN) used in below function:
def mean_image_addition(image, means=(_R_MEAN, _G_MEAN, _B_MEAN)):
The default value is as below
_R_MEAN = 123.68
_G_MEAN = 116.78
_B_MEAN = 103.94

could you please explain more about the value, why they are 123,116,103? Thanks in advance!