import torch


def image_noiser(images, std=0.1):
    """
    Adds random zero-mean Gaussian noise of given standard deviation to image tensor.
    """
    mu = torch.zeros(images.shape)
    sigma = std * torch.ones(images.shape)
    noise = torch.normal(mu, sigma)
    noisy_images = images + noise
    return noisy_images.clamp(-1, 1)