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Python pil example 'normalize'
python normalize
Python pil example: normalize
"""
Reference: https://pytorch.org/docs/master/torchvision/models.html
"""
from urllib.request import urlopen
from PIL import Image
from torchvision import transforms
# Read an example image
url = 'https://raw.githubusercontent.com/quanguet/images/master/cat.jpg'
img = Image.open(urlopen(url)) # PIL Image
# Crop
crop = transforms.transforms.RandomCrop((240, 240))
crop(img) # PIL Image
# ToTensor
totensor = transforms.ToTensor()
"""
Converts a PIL Image or numpy.ndarray (H x W x C) in the range [0, 255]
to a torch.FloatTensor of shape (C x H x W) in the range [0.0, 1.0]
if the PIL Image belongs to one of the modes (L, LA, P, I, F, RGB, YCbCr, RGBA, CMYK, 1)
or if the numpy.ndarray has dtype = np.uint8
"""
type(totensor(img)) # torch.Tensor
# Normalize
"""
Normalize the range [0.0, 1.0] to [-1.0 1.0]
Which channels: [0.485/R, 0.456/G, 0.406/B]
"""
normalize = transforms.Normalize(mean=[0.485, 0.456, 0.406],
std=[0.229, 0.224, 0.225])
normalize(img) # Error since input requires torch.Tensor
type(normalize(totensor(img))) # torch.Tensor
# In Pytorch pretrained models, the standard transforms is as below
# supposed the image is PIL Image in RGB
transforms.Compose([
transforms.ToTensor(),
transforms.Normalize(mean=[0.485, 0.456, 0.406],std=[0.229, 0.224, 0.225])])
Python links
- Learn Python: https://pythonbasics.org/
- Python Tutorial: https://pythonprogramminglanguage.com