Using Datasets, Pipeline, TfmdLists and Transform in computer vision



## Overview

from fastai.vision.all import *


### Creating your own Transform

Creating your own Transform is way easier than you think. In fact, each time you have passed a label function to the data block API or to ImageDataLoaders.from_name_func, you have created a Transform without knowing it. At its base, a Transform is just a function. Let's show how you can easily add a transform by implementing one that wraps a data augmentation from the albumentations library.

First things first, you will need to install the albumentations library. Uncomment the following cell to do so if needed:




Then it's going to be easier to see the result of the transform on a color image bigger than the mnist one we had before, so let's load something from the PETS dataset.

source = untar_data(URLs.PETS)
items = get_image_files(source/"images")


We can still open it with PILIlmage.create:

img = PILImage.create(items[0])
img


We will show how to wrap one transform, but you can as easily wrap any set of transforms you wrapped in a Compose method. Here let's do some ShiftScaleRotate:

from albumentations import ShiftScaleRotate


The albumentations transform work on numpy images, so we just convert our PILImage to a numpy array before wrapping it back in PILImage.create (this function takes filenames as well as arrays or tensors).

aug = ShiftScaleRotate(p=1)
def aug_tfm(img):
np_img = np.array(img)
aug_img = aug(image=np_img)['image']
return PILImage.create(aug_img)

aug_tfm(img)