from fastai.vision.image import TfmPixel
import random

#Contributed by Rani Horev. Thank you!
def _noisify(x, pct_pixels_min:float=0.001, pct_pixels_max:float=0.4, noise_range:int=30):
    if noise_range > 255 or noise_range < 0:
        raise Exception('noise_range must be between 0 and 255, inclusively.')
    h,w = x.shape[1:]
    img_size = h * w
    mult = 10000.0
    pct_pixels = random.randrange(int(pct_pixels_min*mult), int(pct_pixels_max*mult))/mult
    noise_count = int(img_size * pct_pixels)

    for ii in range(noise_count):
        yy = random.randrange(h)
        xx = random.randrange(w)
        noise = random.randrange(-noise_range, noise_range)/255.0
        x[:,yy,xx].add_(noise)
    return x


noisify = TfmPixel(_noisify)