patchify 0.2.3

A library that helps you split image into small, overlappable patches, and merge patches back into the original image.

patchify

patchfy can split images into small overlappable patches by given patch cell size, and merge patches into original image.

This library provides two functions: patchify, unpatchify.

Installation

pip install patchify

Usage

Split image to patches

patchify(image_to_patch, patch_shape, step=1)

2D image:

#This will split the image into small images of shape [3,3]
patches = patchify(image, (3, 3), step=1)

3D image:

#This will split the image into small images of shape [3,3,3]
patches = patchify(image, (3, 3, 3), step=1)

Merge patches into original image

unpatchify(patches_to_merge, merged_image_size)

reconstructed_image = unpatchify(patches, image.shape)

This will reconstruct the original image that was patchified in previous code.

Caveat: in order for unpatchify to work, you need to create patchies with equal step size. e.g. if the original image has width 3 and the patch has width 2, you cannot really create equal step size patches with step size 2. (first patch [elem0, elem1] and second patch [elem2, elem3], which is out of bound).

The required condition for unpatchify to success is to have (width - patch_width) mod step_size = 0.

Full running examples

2D image patchify and merge

import numpy as np
from patchify import patchify, unpatchify

image = np.array([[1,2,3,4], [5,6,7,8], [9,10,11,12]])

patches = patchify(image, (2,2), step=1) # split image into 2*3 small 2*2 patches.

assert patches.shape == (2, 3, 2, 2)
reconstructed_image = unpatchify(patches, image.shape)

assert (reconstructed_image == image).all()

3D image patchify and merge

import numpy as np
from patchify import patchify, unpatchify

image = np.random.rand(512,512,3)

patches = patchify(image, (2,2,3), step=1) # patch shape [2,2,3]
print(patches.shape) # (511, 511, 1, 2, 2, 3). Total patches created: 511x511x1

assert patches.shape == (511, 511, 1, 2, 2, 3)
reconstructed_image = unpatchify(patches, image.shape)
print(reconstructed_image.shape) # (512, 512, 3)

assert (reconstructed_image == image).all()