给图像添加噪声的方法（补充ing）

1.随机修改一部分像素点的灰度值为指定值

def noise(img,proportion=0.05):
    '''
    随机的修改一定数量像素点的灰度值
    :param img:
    :param proportion: 噪声点占全部像素点的比例
    :return:
    '''
    height,width =img.shape[:2]
    num = int(height*width*proportion)#多少个像素点添加噪声
    for k in range(0, num):
        # get the random point
        xi = int(np.random.uniform(0, img.shape[1]))
        xj = int(np.random.uniform(0, img.shape[0]))
        # add noise
        if img.ndim == 2:
            img[xj, xi] = 255
        elif img.ndim == 3:
            img[xj, xi, 0] = 25
            img[xj, xi, 1] = 20
            img[xj, xi, 2] = 20
    return img

　2.椒盐噪声

def salt_and_pepper_noise(img, proportion=0.05):
    '''

    :param img:
    :param proportion: 噪声点占全部像素点的比例
    :return:
    '''
    noise_img =img
    height,width =noise_img.shape[0],noise_img.shape[1]
    num = int(height*width*proportion)#多少个像素点添加椒盐噪声
    for i in range(num):
        w = random.randint(0,width-1)  #随机图片加噪声的位置
        h = random.randint(0,height-1)
        if random.randint(0,1) ==0:
            noise_img[h,w] =0         #加黑点
        else:
            noise_img[h,w] = 255       #加白点
    return noise_img

　　3，高斯噪声