????????一般和transforms.ToTensor()搭配使用

????????作用就是先將輸入歸一化到(0,1)【transforms.ToTensor()】，再使用公式"(x-mean)/std"，將每個元素分布到(-1,1)

? ?很多CV的代碼中，是這樣使用這一條語句的：

torchvision.transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225])

這一組參數(shù)是從ImageNet數(shù)據(jù)集中獲得的

在?torchvision 筆記：ToTensor()_UQI-LIUWJ的博客-CSDN博客的代碼基礎(chǔ)上我們進行修改

ToTensor 中的代碼：

from PIL import Image from torchvision import transforms, utils a=Image.open(b+'img/00000.jpg') a

?

y=transforms.ToTensor() a=y(a) a ''' tensor([[[0.9255, 0.9255, 0.9255, ..., 0.9176, 0.9176, 0.9176],[0.9255, 0.9255, 0.9255, ..., 0.9176, 0.9176, 0.9176],[0.9255, 0.9255, 0.9255, ..., 0.9176, 0.9176, 0.9176],...,[0.7882, 0.7882, 0.7882, ..., 0.7922, 0.7922, 0.7922],[0.7882, 0.7882, 0.7882, ..., 0.7922, 0.7922, 0.7922],[0.7882, 0.7882, 0.7882, ..., 0.7922, 0.7922, 0.7922]],[[0.9255, 0.9255, 0.9255, ..., 0.9216, 0.9216, 0.9216],[0.9255, 0.9255, 0.9255, ..., 0.9216, 0.9216, 0.9216],[0.9255, 0.9255, 0.9255, ..., 0.9216, 0.9216, 0.9216],...,[0.7961, 0.7961, 0.7961, ..., 0.7922, 0.7922, 0.7922],[0.7961, 0.7961, 0.7961, ..., 0.7922, 0.7922, 0.7922],[0.7961, 0.7961, 0.7961, ..., 0.7922, 0.7922, 0.7922]],[[0.9255, 0.9255, 0.9255, ..., 0.9294, 0.9294, 0.9294],[0.9255, 0.9255, 0.9255, ..., 0.9294, 0.9294, 0.9294],[0.9255, 0.9255, 0.9255, ..., 0.9294, 0.9294, 0.9294],...,[0.7922, 0.7922, 0.7922, ..., 0.8000, 0.8000, 0.8000],[0.7922, 0.7922, 0.7922, ..., 0.8000, 0.8000, 0.8000],[0.7922, 0.7922, 0.7922, ..., 0.8000, 0.8000, 0.8000]]]) '''

?Normalize的代碼

z=transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]) a=z(a) a ''' tensor([[[1.9235, 1.9235, 1.9235, ..., 1.8893, 1.8893, 1.8893],[1.9235, 1.9235, 1.9235, ..., 1.8893, 1.8893, 1.8893],[1.9235, 1.9235, 1.9235, ..., 1.8893, 1.8893, 1.8893],...,[1.3242, 1.3242, 1.3242, ..., 1.3413, 1.3413, 1.3413],[1.3242, 1.3242, 1.3242, ..., 1.3413, 1.3413, 1.3413],[1.3242, 1.3242, 1.3242, ..., 1.3413, 1.3413, 1.3413]],[[2.0959, 2.0959, 2.0959, ..., 2.0784, 2.0784, 2.0784],[2.0959, 2.0959, 2.0959, ..., 2.0784, 2.0784, 2.0784],[2.0959, 2.0959, 2.0959, ..., 2.0784, 2.0784, 2.0784],...,[1.5182, 1.5182, 1.5182, ..., 1.5007, 1.5007, 1.5007],[1.5182, 1.5182, 1.5182, ..., 1.5007, 1.5007, 1.5007],[1.5182, 1.5182, 1.5182, ..., 1.5007, 1.5007, 1.5007]],[[2.3088, 2.3088, 2.3088, ..., 2.3263, 2.3263, 2.3263],[2.3088, 2.3088, 2.3088, ..., 2.3263, 2.3263, 2.3263],[2.3088, 2.3088, 2.3088, ..., 2.3263, 2.3263, 2.3263],...,[1.7163, 1.7163, 1.7163, ..., 1.7511, 1.7511, 1.7511],[1.7163, 1.7163, 1.7163, ..., 1.7511, 1.7511, 1.7511],[1.7163, 1.7163, 1.7163, ..., 1.7511, 1.7511, 1.7511]]]) '''

將tensor反變換回圖片，則有

?

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