# -*- coding: utf-8 -*-
# File: noise.py
import numpy as np
import cv2
from .base import PhotometricAugmentor
__all__ = ['JpegNoise', 'GaussianNoise', 'SaltPepperNoise']
class JpegNoise(PhotometricAugmentor):
""" Random JPEG noise. """
def __init__(self, quality_range=(40, 100)):
"""
Args:
quality_range (tuple): range to sample JPEG quality
"""
super(JpegNoise, self).__init__()
self._init(locals())
def _get_augment_params(self, img):
return self.rng.randint(*self.quality_range)
def _augment(self, img, q):
enc = cv2.imencode('.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, q])[1]
return cv2.imdecode(enc, 1).astype(img.dtype)
class GaussianNoise(PhotometricAugmentor):
"""
Add random Gaussian noise N(0, sigma^2) of the same shape to img.
"""
def __init__(self, sigma=1, clip=True):
"""
Args:
sigma (float): stddev of the Gaussian distribution.
clip (bool): clip the result to [0,255] in the end.
"""
super(GaussianNoise, self).__init__()
self._init(locals())
def _get_augment_params(self, img):
return self.rng.randn(*img.shape)
def _augment(self, img, noise):
old_dtype = img.dtype
ret = img + noise * self.sigma
if self.clip or old_dtype == np.uint8:
ret = np.clip(ret, 0, 255)
return ret.astype(old_dtype)
class SaltPepperNoise(PhotometricAugmentor):
""" Salt and pepper noise.
Randomly set some elements in image to 0 or 255, regardless of its channels.
"""
def __init__(self, white_prob=0.05, black_prob=0.05):
"""
Args:
white_prob (float), black_prob (float): probabilities setting an element to 255 or 0.
"""
assert white_prob + black_prob <= 1, "Sum of probabilities cannot be greater than 1"
super(SaltPepperNoise, self).__init__()
self._init(locals())
def _get_augment_params(self, img):
return self.rng.uniform(low=0, high=1, size=img.shape)
def _augment(self, img, param):
img[param > (1 - self.white_prob)] = 255
img[param < self.black_prob] = 0
return img
