• PIL：使用python自帶影象處理庫讀取出來的圖片格式
• numpy：使用python-opencv庫讀取出來的圖片格式
• tensor：pytorch中訓練時所採取的向量格式（當然也可以說圖片）

PIL與Tensor相互轉換

import torch
from PIL import Image
import matplotlib.pyplot as plt

# loader使用torchvision中自帶的transforms函式
loader = transforms.Compose([
 transforms.ToTensor()]) 

unloader = transforms.ToPILImage()

# 輸入圖片地址
# 返回tensor變數
def image_loader(image_name):
 image = Image.open(image_name).convert('RGB')
 image = loader(image).unsqueeze(0)
 return image.to(device,torch.float)

# 輸入PIL格式圖片
# 返回tensor變數
def PIL_to_tensor(image):
 image = loader(image).unsqueeze(0)
 return image.to(device,torch.float)

# 輸入tensor變數
# 輸出PIL格式圖片
def tensor_to_PIL(tensor):
 image = tensor.cpu().clone()
 image = image.squeeze(0)
 image = unloader(image)
 return image

#直接展示tensor格式圖片
def imshow(tensor,title=None):
 image = tensor.cpu().clone() # we clone the tensor to not do changes on it
 image = image.squeeze(0) # remove the fake batch dimension
 image = unloader(image)
 plt.imshow(image)
 if title is not None:
 plt.title(title)
 plt.pause(0.001) # pause a bit so that plots are updated

#直接儲存tensor格式圖片
def save_image(tensor,**para):
 dir = 'results'
 image = tensor.cpu().clone() # we clone the tensor to not do changes on it
 image = image.squeeze(0) # remove the fake batch dimension
 image = unloader(image)
 if not osp.exists(dir):
 os.makedirs(dir)
 image.save('results_{}/s{}-c{}-l{}-e{}-sl{:4f}-cl{:4f}.jpg'
  .format(num,para['style_weight'],para['content_weight'],para['lr'],para['epoch'],para['style_loss'],para['content_loss']))

numpy 與 tensor相互轉換

import cv2
import torch
import matplotlib.pyplot as plt

def toTensor(img):
 assert type(img) == np.ndarray,'the img type is {},but ndarry expected'.format(type(img))
 img = cv2.cvtColor(img,cv2.COLOR_BGR2RGB)
 img = torch.from_numpy(img.transpose((2,1)))
 return img.float().div(255).unsqueeze(0) # 255也可以改為256

def tensor_to_np(tensor):
 img = tensor.mul(255).byte()
 img = img.cpu().numpy().squeeze(0).transpose((1,2,0))
 return img

def show_from_cv(img,title=None):
 img = cv2.cvtColor(img,cv2.COLOR_BGR2RGB)
 plt.figure()
 plt.imshow(img)
 if title is not None:
 plt.title(title)
 plt.pause(0.001)


def show_from_tensor(tensor,title=None):
 img = tensor.clone()
 img = tensor_to_np(img)
 plt.figure()
 plt.imshow(img)
 if title is not None:
 plt.title(title)
 plt.pause(0.001)

N張圖片一起轉換.

# 將 N x H x W X C 的numpy格式圖片轉化為相應的tensor格式
def toTensor(img):
 img = torch.from_numpy(img.transpose((0,3,1,2)))
 return img.float().div(255).unsqueeze(0)

參考:https://www.jb51.net/article/177291.htm

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