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preloadImage()

此函数是 @remotion/preload 包的一部分。

🌐 This function is part of the @remotion/preload package.

此功能会预加载图片，以便当<Img>标签挂载时，它可以立即显示。

🌐 This function preloads an image so that when an <Img> tag is mounted, it can display immediately.

虽然预加载对于渲染不是必要的，但它可以帮助在 <Player /> 和 Studio 中实现无缝播放。

🌐 While preload is not necessary for rendering, it can help with seamless playback in the <Player /> and in the Studio.

preloadImage() 的一个替代方案是 prefetch() API。请参阅 @remotion/preload vs prefetch() 来决定哪一个更适合你的使用场景。

🌐 An alternative to preloadImage() is the prefetch() API. See @remotion/preload vs prefetch() to decide which one is better for your usecase.

用法​

🌐 Usage

import { preloadImage } from "@remotion/preload";

const unpreload = preloadImage(
  "https://images.unsplash.com/photo-1561336313-0bd5e0b27ec8?ixlib=rb-4.0.3&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1740&q=80"
);

// If you want to un-preload the image later
unpreload();

它是如何运作的​

🌐 How it works

一个 <link rel="preload" as="image"> 标签被添加到文档的头部元素中。

🌐 A <link rel="preload" as="image"> tag gets added to the head element of the document.

处理重定向​

🌐 Handle redirects

如果图片 URL 重定向到另一个 URL，预加载原始 URL 将无效。

🌐 If the image URL redirects to another URL, preloading the original URL does not work.

如果你包含的 URL 是未知的，请使用 resolveRedirect() 来通过编程方式获取可能重定向后的最终 URL。

🌐 If the URL you include is unknown, use resolveRedirect() to programmatically obtain the final URL following potential redirects.

如果资源不支持 CORS，resolveRedirect() 将会失败。如果资源发生重定向，并且不支持 CORS，则无法预加载该资源。

🌐 If the resource does not support CORS, resolveRedirect() will fail. If the resource redirects, and does not support CORS, you cannot preload the asset.

这段代码尝试以最佳努力的方式预加载一张图片。如果重定向无法解析，它会尝试预加载原始 URL。

🌐 This snippet tries to preload a image on a best-effort basis. If the redirect cannot be resolved, it tries to preload the original URL.

import { preloadImage, resolveRedirect } from "@remotion/preload";
import { Img } from "remotion";

// This code gets executed immediately once the page loads
let urlToLoad =
  "https://images.unsplash.com/photo-1561336313-0bd5e0b27ec8?ixlib=rb-4.0.3&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1740&q=80";

resolveRedirect(urlToLoad)
  .then((resolved) => {
    // Was able to resolve a redirect, setting this as the image to load
    urlToLoad = resolved;
  })
  .catch((err) => {
    // Was unable to resolve redirect e.g. due to no CORS support
    console.log("Could not resolve redirect", err);
  })
  .finally(() => {
    // In either case, we try to preload the original or resolved URL
    preloadImage(urlToLoad);
  });

// This code only executes once the component gets mounted
const MyComp: React.FC = () => {
  // If the component did not mount immediately, this will be the resolved URL.

  // If the component mounted immediately, this will be the original URL.
  // In that case preloading is ineffective anyway.
  return <Img src={urlToLoad}></Img>;
};

另请参阅​

🌐 See also

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