踩坑：skimage中对图像做的归一化处理

 skimage在读使用io.imread读取灰度图像时（as_grey=True / as_gray=True）会做归一化处理数据类型转化为float64；

图像缩放transform.resize同样会将uint8的图像转化为float64类型，这里注意的是！！！！！！！如果已经归一化，但是类型依然是uint8的图像，在缩放之后图像的范围将不再是（0-1）。

总结：skimage需要慎用，cv2，PIL都挺好用的！

import skimage
from skimage import io,transform
import numpy as np
image= io.imread('test.jpg',as_grey=False)
# 第一个参数是文件名可以是网络地址，第二个参数默认为False，True时为灰度图
print type(image) # out: numpy.ndarray
print image.dtype # out: dtype('uint8')
print image.shape # out: (300, 400, 3) (h,w,c)前面介绍了ndarray的特点
# mode也是RGB
print image
'''
注意此时image里都是整数uint8,范围[0-255]
array([
        [ [143, 198, 201 (dim=3)],[143, 198, 201],... (w=200)],
        [ [143, 198, 201],[143, 198, 201],... ],
        ...(h=100)
      ], dtype=uint8)

'''
image= io.imread('test.jpg',as_grey=True)
print image.shape # out: (300, 400)
print image
'''
此时image范围变为[0-1]
array([[ 0.73148549,  0.73148549,  0.73148549, ...,  0.73148549,
         0.73148549,  0.73148549],
       [ 0.73148549,  0.73148549,  0.73148549, ...,  0.73148549,
       .....]])
'''
print image.dtype # out: dtype('float64')

image = io.imread('test.jpg',as_grey=False) 
# h*w
image = transform.resize(image,(100, 200),order=1)　# order默认是1，双线性
#resize后image范围又变成[0-1]
print image.dtype # out: dtype('float64')
print image.shape # out: (100, 200, 3)
print image
'''
array([[[ 0.56078431,  0.77647059,  0.78823529],
        [ 0.56078431,  0.77647059,  0.78823529],
        [ 0.56078431,  0.77647059,  0.78823529],
        ..., ...]])
'''
'''
resize函数接口
resize(image, output_shape, order=1, mode='constant', cval=0, clip=True, preserve_range=False)
order : int, optional
        The order of interpolation. The order has to be in the range 0-5:
         - 0: Nearest-neighbor
         - 1: Bi-linear (default)
         - 2: Bi-quadratic
         - 3: Bi-cubic
         - 4: Bi-quartic
         - 5: Bi-quintic

'''
print skimage.img_as_float(image).dtype # out: float64
# img_as_float可以把image转为double，即float64
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作者：爆米花好美啊 
来源：优快云 
原文：https://blog.youkuaiyun.com/u013010889/article/details/54347089 
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