使用Python批量转换图片格式

PNG 创建于 1995 年，是用于在网络上传输图像的 GIF 格式的免费替代品。因为PNG没专利，所以编辑和查看PNG也不需要许可。PNG图像在压缩时不会丢失任何数据，编码、解码方式一样。与JPEG 文件等有损选项相比，这是一个很大的优势。

所以，要想把其它格式的图片转换为PNG格式是很方便的。除了一种情况，那就是图片比较多的时候。这时需要一些工具来帮助我们批量转换。很多解决方案都需要安装什么软件，下面这种，额……也需要安装，除此之外还得安装一个包：

pip install pillow

然后编写和执行脚本：

from multiprocessing import Pool
import os
import re
from PIL import Image


def save_single(
    root: str, source_filename: str, suffix: str, target_path: str, target_suffix: str=png
):
    try:
        img = Image.open(os.path.join(root, source_filename+suffix))
        img = img.convert(RGB)
        img.save(os.path.join(target_path, f{
            
     source_filename}.{
            
     target_suffix}), target_suffix)
    except Exception as e:
        print(e)
        return e
    return False


def copy_single(
    root: str, source_filename: str, target_path: str
):
    try:
        with open(os.path.join(root, source_filename), rb) as file:
            read = file.read()
        with open(os.path.join(target_path, source_filename), wb) as file:
            file.write(read)
    except Exception as e:
        print(e)
        return e
    return False


def run(source_path: str, target_path: str, pool):
    file_paths = []
    source_path_len = len(source_path)
    if not(source_path.endswith(/) or source_path.endswith(\)):
        source_path_len += 1
    if not os.path.exists(target_path):
        os.makedirs(target_path)
    for root, directories, files in os.walk(source_path):
        for file in files:
            path = root[source_path_len:] # 去掉要被替换掉的目录前缀
            target_directory = os.path.join(target_path, path) # 这是新目录，要保存的位置
            file_paths.append((root, file, target_directory))
        for directory in directories: # 创建目录，要是把所有文件保存在同目录下，同名文件会冲突
            source_path = os.path.join(root, directory)
            path = source_path[source_path_len:]
            target_directory = os.path.join(target_path, path)
            if not os.path.exists(target_directory):
                os.makedirs(target_directory)
    for root, file, target in file_paths:
        fname, suffix = os.path.splitext(file)
        lower_suffix = suffix.lower()
        if lower_suffix in (.jpg, .jpeg, .bmp):
            pool.apply_async(save_single, (root, fname, suffix, target))
        else:
            pool.apply_async(copy_single, (root, file, target))


SOURCE_PATH = /home/ubuntu/example/Download # 一个目录，脚本会递归地访问这文件夹里的图片
TARGET_PATH = /home/ubuntu/example/project/assets # 脚本会在转换的时候把原来目录的结构都复刻进来，也就是说转换前后各个图片的相对位置没变

if __name__ == "__main__":
    pool = Pool(8) # 这个8是进程池的大小，根据电脑核数和内存以及磁盘转速来选
    run(SOURCE_PATH, TARGET_PATH, pool)
    pool.close()
    pool.join()