I sample 10w images (448*448) from Imagenet, and use the following transform to calculate mean and std, but I get quite different results (for example, the first number in mean is -6.0, while it is -8.8 in init.py) .
array([-6.03033250e+00, 1.29993835e-02, 1.49537622e-02, 1.51799573e-02,
-1.13648491e-04, 1.54878503e-02, 1.53720154e-02, 1.53556921e-02,
2.81915356e-02, 1.60401630e-04, -4.44463577e-04, -1.01026878e-04,
5.11066914e-05, -1.98013484e-06, -3.41422224e-05, -2.58331299e-07,
1.10180435e-03, 2.21792049e-04, 1.39479723e-04, -8.06250381e-05,
-2.07372379e-04, -1.05006399e-04, -5.55165100e-05, -6.47384501e-05,
2.58280060e-03, -1.80571003e-04, 1.18345385e-04, 1.12984667e-04,
-9.14287949e-05, 4.99107647e-05, 8.15401077e-05, 9.16138768e-06,
-2.27722988e-04, 1.57206738e-02, 1.47642676e-02, 1.54191162e-02,
-4.14411783e-05, 1.51528882e-02, 1.46344177e-02, 1.49200305e-02,
6.63593979e-04, 4.27199173e-05, 1.16677284e-04, 6.97712183e-06,
3.13424659e-05, -1.30740047e-05, 4.64571810e-05, -1.42793226e-05,
9.56597519e-05, -4.12341833e-05, -5.65912151e-05, -4.26276398e-05,
3.67857361e-05, -2.01084042e-05, -1.99776542e-05, -4.22449780e-05,
2.81112843e-04, -3.76434875e-05, 6.74299002e-05, -1.70663524e-05,
7.03380299e-05, -4.41773653e-05, -1.28061640e-05, 2.91422606e-05,
-4.79707900e+01, -1.56035420e-01, 1.84412866e-02, -1.81954609e-01,
8.18166809e-04, -2.88985859e-01, 1.66051001e-02, -8.56152500e-01,
2.55319219e-01, 6.34916153e-04, -6.54642410e-04, -3.67918243e-04,
-1.46316862e-04, 4.28928223e-04, 8.34166408e-06, 6.26668053e-04,
3.02419678e-03, 3.90776024e-04, 6.26678009e-04, -2.69588165e-04,
-4.69866219e-04, 1.35695171e-04, -7.54751015e-05, 2.07719803e-04,
2.63585474e-02, -4.98884430e-04, 7.94840765e-05, 4.33962746e-04,
-9.15148163e-05, -4.85011435e-05, 1.71204340e-05, 7.87531233e-05,
3.61622124e-04, 1.60066968e-02, 1.53226550e-02, 1.57744312e-02,
-1.57388401e-04, 1.57735291e-02, 1.55607458e-02, 1.59658862e-02,
7.61185242e-03, 7.60141182e-05, 1.83090401e-04, 2.97386026e-05,
1.29148855e-04, -2.14893079e-05, -8.30834389e-05, -2.46814802e-06,
-4.37176418e-05, -7.39859772e-05, 1.27551041e-04, 1.38395560e-05,
2.68336916e-05, 3.96110487e-05, 4.98725027e-06, 5.02774382e-05,
2.35398788e-03, 4.50284004e-05, 4.04752493e-05, -7.75732183e-05,
-3.65114021e-05, 4.00702047e-05, -1.35714030e-05, -6.49227858e-06,
-4.03517225e+01, -1.11374043e-01, 1.59219690e-02, -1.36966182e-01,
1.23506355e-05, -2.23436934e-01, 1.54884302e-02, -6.65007500e-01,
4.89485303e-02, 4.99520540e-05, 2.91033287e-04, 2.53711338e-04,
7.27137375e-05, 1.61097932e-05, -3.57716489e-05, 4.53832970e-04,
-4.07430267e-04, -1.03491755e-04, -1.29601517e-04, 6.75728321e-05,
1.41087322e-04, 3.39652328e-04, 2.33641863e-05, 8.59971695e-04,
5.30565369e-03, 3.57365084e-05, -7.69644356e-05, -5.08962917e-05,
-2.04017639e-05, 4.38169384e-05, -6.81887770e-05, 2.54687166e-05,
1.86980667e-04, 1.57325134e-02, 1.46990674e-02, 1.51832434e-02,
3.39924145e-05, 1.47439392e-02, 1.39994238e-02, 1.47644763e-02,
1.93976776e-03, 6.48592949e-06, -5.98660469e-05, 7.06000447e-06,
-1.71651232e-05, 1.77008224e-05, 1.34183979e-05, -1.78827178e-05,
6.76107407e-07, 1.38425112e-05, 3.02519321e-05, 4.65274429e-05,
-2.75446343e-05, 3.41837192e-05, 1.75191140e-05, 1.25331631e-04,
3.84187164e-04, 2.43143845e-05, -3.01020527e-05, 7.12374985e-06,
-7.48400331e-06, 5.84180713e-06, 1.81409192e-05, 3.42158675e-06])
array([ 82.38169827, 11.38608322, 5.81470583, 3.52816731,
2.28901719, 1.49236127, 1.08501744, 0.93430705,
11.9924049 , 5.79940342, 3.82653512, 2.57590202,
1.75848328, 1.19242361, 0.89143787, 0.78188766,
6.17919321, 3.91159174, 2.92009203, 2.12184516,
1.50184193, 1.0502063 , 0.80137738, 0.71105992,
3.79255235, 2.68489233, 2.16317836, 1.67390197,
1.2370023 , 0.89879742, 0.70613112, 0.63874275,
2.4841856 , 1.85924305, 1.55564345, 1.25683596,
0.97185804, 0.74702268, 0.61385155, 0.57088932,
1.62551123, 1.27050052, 1.09685006, 0.92327635,
0.7542027 , 0.62263785, 0.54023429, 0.51832272,
1.1820139 , 0.95243114, 0.8406118 , 0.73182664,
0.6246161 , 0.54960161, 0.49839851, 0.48895034,
1.00303605, 0.82013756, 0.73174628, 0.6499707 ,
0.57257392, 0.51675503, 0.47800795, 0.47636717,
259.36079478, 38.44986519, 19.16965258, 10.89434406,
6.43545545, 3.66728131, 2.2594354 , 1.67022082,
40.60415659, 19.00020315, 11.99398764, 7.44093844,
4.56251835, 2.660099 , 1.66803618, 1.24568483,
20.39905466, 12.24901995, 8.65123948, 5.75999435,
3.63950595, 2.17124496, 1.38173622, 1.04991463,
11.63568499, 7.69741319, 5.84057403, 4.13102437,
2.70702985, 1.66560499, 1.09088518, 0.85387174,
6.88068855, 4.7445341 , 3.71515009, 2.7268528 ,
1.85518841, 1.19665103, 0.82843158, 0.68215483,
3.91339393, 2.77513896, 2.22651773, 1.68565288,
1.20127373, 0.83837315, 0.63520696, 0.56045151,
2.40690855, 1.73863335, 1.41733271, 1.10696651,
0.83259191, 0.63906468, 0.53207093, 0.49742473,
1.73745029, 1.28346151, 1.06528646, 0.85709265,
0.67805348, 0.5552189 , 0.4881204 , 0.47174586,
122.72236084, 15.16835772, 7.08301888, 3.80431485,
2.17961708, 1.25995895, 0.8367607 , 0.77972808,
16.04436612, 7.17905356, 4.3238403 , 2.56993457,
1.55470093, 0.94589099, 0.66617143, 0.58821462,
7.58912016, 4.44666898, 3.04147918, 1.96773926,
1.24167036, 0.79642635, 0.58626616, 0.53091011,
4.13914657, 2.71065144, 2.01906855, 1.41162135,
0.94801087, 0.65401318, 0.51175742, 0.48173046,
2.3989198 , 1.66442266, 1.29721596, 0.96672071,
0.70264342, 0.53906953, 0.45475156, 0.44528184,
1.38069485, 1.01322971, 0.83189345, 0.67026537,
0.54118055, 0.46403401, 0.41805331, 0.42281751,
0.90856605, 0.70672666, 0.60918523, 0.52767384,
0.45933229, 0.42762222, 0.40134326, 0.41231353,
0.71600727, 0.58663444, 0.52283646, 0.47365366,
0.4332441 , 0.41275816, 0.39301931, 0.40753712])