如何在@11ty/eleventy img中为我处理过的镜像指定outputDir？

const Image = require("@11ty/eleventy-img");

module.exports = function(eleventyConfig) {
  eleventyConfig.addPassthroughCopy("images");
  
  eleventyConfig.addNunjucksAsyncShortcode("myImage", async function(src, alt, sizes = "100vw") {
    if (src && alt) {
      let metadata = await Image(src, {
        widths: [300, 600, 1200],
        formats: ["avif", "jpeg"],
        outputDir: "_site/images" // 指定输出目录
      });

      let imageAttributes = {
        alt,
        sizes,
        loading: "lazy",
        decoding: "async",
      };

      return Image.generateHTML(metadata, imageAttributes);
    }
    
    return "";
  });
};