如何保持图片比例，并根据图片的实际大小调整图片大小？

from PIL import Image

def resize_image(image_path, target_width, target_height):
    # 打开图片
    image = Image.open(image_path)
    
    # 获取原始宽度和高度
    original_width, original_height = image.size
    
    # 计算宽高比例
    aspect_ratio = original_width / original_height
    
    # 根据目标宽度或高度计算另一个目标尺寸
    if target_width is not None:
        target_height = int(target_width / aspect_ratio)
    elif target_height is not None:
        target_width = int(target_height * aspect_ratio)
    
    # 调整图片大小
    resized_image = image.resize((target_width, target_height))
    
    # 保存调整后的图片
    resized_image.save("resized_image.jpg")
    
    # 关闭图片
    image.close()

# 调用函数进行图片尺寸调整
resize_image("original_image.jpg", target_width=800, target_height=None)