什么是马赛克图片？如果用Python把21057张图片合成一张，会是什么样的

import cv2
import glob
import argparse
import numpy as np
from tqdm import tqdm  # 进度条
from itertools import product  # 迭代器

def parsArgs():
    parser = argparse.ArgumentParser('拼接马赛克图片')
    parser.add_argument('--targetpath', type=str, default='examples/3.jpg', help='目标图像路径')
    parser.add_argument('--outputpath', type=str, default='output.jpg', help='输出图像的路径')
    parser.add_argument('--sourcepath', type=str, default='sourceimages', help='用来拼接图像的所有源图像文件路径')
    parser.add_argument('--blocksize', type=int, default=15, help='马赛克快的大小')

    args = parser.parse_args()

    return args

def readSourceImages(sourcepath,blocksize):
    print('开始读取图像')

sourceimages = []

avgcolors = []

for path in tqdm(glob.glob("{}/*.jpg".format(sourcepath))):
    image = cv2.imread(path, cv2.IMREAD_COLOR)
    if image.shape[-1] != 3:
        continue
    # 缩放尺寸
    image = cv2.resize(image, (blocksize, blocksize))
    # 图像颜色平均值
    avgcolor = np.sum(np.sum(image, axis=0), axis=0) / (blocksize * blocksize)
    sourceimages.append(image)
    avgcolors.append(avgcolor)
print('结束读取')
return sourceimages,np.array(avgcolors)

def main(args):
    targetimage = cv2.imread(args.targetpath)
    outputimage = np.zeros(targetimage.shape,np.uint8)  # int8 int16 int32 int64
    sourceimages,avgcolors = readSourceImages(args.sourcepath,args.blocksize)
    print('开始制作')
    for i, j in tqdm(product(range(int(targetimage.shape[1]/args.blocksize)), range(int(targetimage.shape[0]/args.blocksize)))):
        block = targetimage[j * args.blocksize: (j + 1) * args.blocksize, i * args.blocksize: (i + 1) * args.blocksize,:]
        avgcolor = np.sum(np.sum(block, axis=0), axis=0) / (args.blocksize * args.blocksize)
        distances = np.linalg.norm(avgcolor - avgcolors, axis=1)
        idx = np.argmin(distances)
        outputimage[j * args.blocksize: (j + 1) * args.blocksize, i * args.blocksize: (i + 1) * args.blocksize, :] = \
        sourceimages[idx]
    cv2.imwrite(args.outputpath, outputimage)
    cv2.imshow('result', outputimage)
    print('制作完成')

if __name__ == '__main__':
    # run
    main(parseArgs())