How to Restore resized images to original size

Hi, I’ve an image (extracted from pointcloud) which I’ve resized for UNet training. I used the following to resize all dataset’s images and target images

img_square = imresize(img_source, (400, 400));

I’m not sure how to get the image back to actual size? (so that I can extract semantic segmentation information from each pixel and map it back to pointcloud)