python多线程图片处理

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已于 2022-01-24 18:38:09 修改

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分类专栏：实用代码文章标签： python 计算机视觉

于 2022-01-24 18:37:03 首次发布

本文链接：https://blog.youkuaiyun.com/weixin_44326452/article/details/122672935

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本文介绍了一种利用多线程技术对大量图片进行高效压缩的方法。通过将任务分配给多个线程并行处理，显著提高了处理速度。文章提供了一个具体的Python实现案例，包括如何读取图片、设置压缩质量及保存压缩后的图片。

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有时候我们需要对图片进行如加噪、放缩等变换，当数据集比较大时，遍历整个数据集所用时间太长，为此可以写一点多线程处理的代码，下面以压缩为例子：

# author: Wu
# 2022/1/24
# This script is used to jpeg compress

import os
import cv2
import numpy as np
from threading import Thread

input_folder = '/data0/wjh/coco/val2017'
output_jpg50_folder = '/data0/wjh/coco/val2017-jpg50'
output_jpg70_folder = '/data0/wjh/coco/val2017-jpg70'
num_threads = 5


def jpg_compress(filelist):
    for file in filelist:
        img = cv2.imread(os.path.join(input_folder, file))
        new_jpg50name = os.path.join(output_jpg50_folder, file.split('.')[0]+'.jpg')
        new_jpg70name = os.path.join(output_jpg70_folder, file.split('.')[0]+'.jpg')
        cv2.imwrite(new_jpg50name, img, [int(cv2.IMWRITE_JPEG_QUALITY), 50])
        cv2.imwrite(new_jpg70name, img, [int(cv2.IMWRITE_JPEG_QUALITY), 70])

def multi_thread_process():
    if num_threads == 1:
        jpg_compress(os.listdir(input_folder))
        return
    filelist_total = os.listdir(input_folder)
    filenum = len(filelist_total)
    filenum_each_thread = int(filenum/num_threads)
    thread_list = []
    for i in range(num_threads-1):
        thread_list.append(Thread(target=jpg_compress, args=(filelist_total[i*filenum_each_thread : (i+1)*filenum_each_thread],)))
    thread_list.append(Thread(target=jpg_compress, args=(filelist_total[(num_threads-1)*filenum_each_thread :],)))
    for th in thread_list:
        th.start()
    for th in thread_list:
        th.join()

multi_thread_process()