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preloadImage()

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

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

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

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

Usage​

tsx
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();
tsx
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();

How it works​

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

Handle redirects​

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

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

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

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.

tsx
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>;
};
tsx
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>;
};

See also​