Slicing image into square patches

1

Is there a slicing function to slice an image into square patches of size p. Right now I am doing this in few lines of code but if there is a function that does this I would just replace.

2

Look into torchvision.transforms.*crop methods. http://pytorch.org/docs/master/torchvision/transforms.html
Afaik, there is no default method for an arbitrary location crop, but it is easily implementable using torchvision.transforms.Lambda.

3

Quite late but for reference for others, you can use the unfold function:

patches = img_t.data.unfold(0, 3, 3).unfold(1, 8, 8).unfold(2, 8, 8)

Here is the demo code to test:

import torch
from torchvision import transforms
import matplotlib.pyplot as plt

%matplotlib inline

transt = transforms.ToTensor()
transp = transforms.ToPILImage()
img_t = transt(Image.open('cifar/train/10000_automobile.png'))

#torch.Tensor.unfold(dimension, size, step)
#slices the images into 8*8 size patches
patches = img_t.data.unfold(0, 3, 3).unfold(1, 8, 8).unfold(2, 8, 8)


print(patches[0][0][0].shape)

def visualize(patches):
    """Imshow for Tensor."""    
    fig = plt.figure(figsize=(4, 4))
    for i in range(4):
        for j in range(4):
            inp = trans1(patches[0][i][j])
            inp = np.array(inp)

            ax = fig.add_subplot(4, 4, ((i*4)+j)+1, xticks=[], yticks=[])
            plt.imshow(inp)

visualize(patches)
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