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""" | |
scale_images.py | |
Function to scale any image to the pixel values of [-1, 1] for GAN input. | |
Author: liuhh02 https://machinelearningtutorials.weebly.com/ | |
""" | |
from PIL import Image | |
import numpy as np | |
from os import listdir | |
def normalize(arr): | |
''' Function to scale an input array to [-1, 1] ''' | |
arr_min = arr.min() | |
arr_max = arr.max() | |
# Check the original min and max values | |
print('Min: %.3f, Max: %.3f' % (arr_min, arr_max)) | |
arr_range = arr_max - arr_min | |
scaled = np.array((arr-arr_min) / float(arr_range), dtype='f') | |
arr_new = -1 + (scaled * 2) | |
# Make sure min value is -1 and max value is 1 | |
print('Min: %.3f, Max: %.3f' % (arr_new.min(), arr_new.max())) | |
return arr_new | |
# path to folder containing images | |
path = './directory/to/image/folder/' | |
# loop through all files in the directory | |
for filename in listdir(path): | |
# load image | |
image = Image.open(path + filename) | |
# convert to numpy array | |
image = np.array(image) | |
# scale to [-1,1] | |
image = normalize(image) |
Hello @liuhh02, would it be possible to identify in your code what parameters I would need to change should I require a different scale of values other than [-1 1].
Sure! This line of code scales the values to [0, 1]:
scaled = np.array((arr-arr_min) / float(arr_range), dtype='f')
So you may modify
arr_new = -1 + (scaled * 2)
accordingly to scale it to the range you require.
@liuhh02 Nice approach, thank you for your input
Thanks to @liuhh02 and @JohanRaniseth for the work. For anyone visiting in the future: you have to normalize based on the min and max of your whole (training) dataset, not every image individually like in the code provided above (see #950). If you normalize individually, you will lose information and be unable to reverse the process later.
I also had to make another change to the tensor2im function in util.py by changing this line to just return image_numpy.
Hello @liuhh02, would it be possible to identify in your code what parameters I would need to change should I require a different scale of values other than [-1 1].