使用Python的PIL如何将数组输出图像

import numpy as np
from PIL import Image
 
map_data = np.loadtxt("./city_map.txt")
map_data = map_data.tolist()
 
# 填充地图数组的颜色通道
for i in range(2400):
    for j in range(2400):
        value = int(map_data[i][j])
        if value == 0:  # 如果地图值为0，显示黑色
            map_data[i][j] = [0, 0, 0]
        else:           # 将流量低的区域根据区域号码来填充RGB三通道
            r = (value % 255) * 50 % 255        # 取模乘以50再取模作为R通道
            g = (value // 255) * 50 + 100       # 取整加100作为G通道的值
            b = value % 255                     # 取模作为B通道的值
            map_data[i][j] = [r, g, b]
 
# 输出png图像
map_data = np.array(map_data)
map_data = np.asarray(map_data, np.uint8)
pic = Image.fromarray(map_data)
pic.save('city.png')

    map_data = np.loadtxt("./city.txt")
    map_data = map_data.tolist()
    max_flow = flow_data.max()
    for i in range(2400):
        for j in range(2400):
            area = int(map_data[i][j])
            flow_value = flow_data[area - 1]   # 根据地图区域索引读取值
            if area == 0:  # 如果地图值为0，显示黑色
                map_data[i][j] = [0, 0, 0]
            else:  # 根据区域流量值来填充RGB三通道
                r = 255 - flow_value / max_flow * 255
                g = 255
                b = 255
                map_data[i][j] = [r, g, b]
    # 输出png图像
    map_data = np.array(map_data)
    map_data = np.asarray(map_data, np.uint8)
    pic = Image.fromarray(map_data)
    pic.save('./output/' + flow_type + '_flow_map.png')