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from PIL import Image
import numpy as np

img = Image.open("image.jpg")       # PIL.Image 对象
img = img.resize((640, 640))        # 调整尺寸
arr = np.array(img)                 # 转 numpy（RGB，HWC）

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import cv2

img = cv2.imread("image.jpg")       # BGR，numpy 数组
img_rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
img_resized = cv2.resize(img, (640, 640))
cv2.imwrite("out.jpg", img)         # 保存（需 BGR）

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import matplotlib.pyplot as plt

img = plt.imread("image.jpg")       # RGB，numpy 数组
plt.imshow(img)
plt.axis("off")
plt.show()

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from torchvision.io import read_image
from torchvision.transforms import Resize

img = read_image("image.jpg")       # CHW，torch.uint8
img = Resize((640, 640))(img)       # 调整尺寸
img = img.float() / 255.0           # 归一化