Update Node.js examples to use AVIF

[lilouartz]

Hey!

Thank you for the wonderful library.

I just posted a blog post that shows how using AVIF with thumbhash produces 50% smaller images.

https://pillser.com/engineering/2024-06-20-optimizing-image-loading-with-avif-placeholders-for-enhanced-performance

Perhaps it should be the default?

[Green-Sky]

The idea is to transmit the hash, not the image of the decoded hash. Assuming you are in fact generating them on the server.

[lilouartz]

@Green-Sky Could you elaborate? I am not confident that I am following

[Green-Sky]

It reads like you are rendering the thumbhash to png/avif on the server side and then send it as part of the html to the client.

What you really want to do, if you are not doing it, is send the thumbhash to the client and then run some js that renders the image on the client.

also this issue might be of interest to you: https://github.com/evanw/thumbhash/issues/33

[lilouartz]

oh that was not obvious at all. hah!

Well, I need to update the article it seems.

[lilouartz]

so, on the client side I would do something like this?

const base64ToUint8Array = (base64: string) => {
  const binaryString = atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }

  return bytes;
};

const dataUrl = thumbHashToDataURL(
  base64ToUint8Array('a/cNG4L1NUOKhahX+XncHfg='),
);

[lilouartz]

This is what I have so far...

const base64ToUint8Array = (base64: string): Uint8Array => {
  const binaryString = atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    // eslint-disable-next-line unicorn/prefer-code-point
    bytes[i] = binaryString.charCodeAt(i);
  }

  return bytes;
};

const dataURLtoBlob = (dataURI: string): Blog => {
  const mime = dataURI.split(',')[0].split(':')[1].split(';')[0];
  const binary = atob(dataURI.split(',')[1]);
  const array = [];

  for (let i = 0; i < binary.length; i++) {
    // eslint-disable-next-line unicorn/prefer-code-point
    array.push(binary.charCodeAt(i));
  }

  return new Blob([new Uint8Array(array)], { type: mime });
};

const SupplementImage = ({
  image,
  loadingStrategy,
}: {
  readonly image: Image;
  readonly loadingStrategy: LoadingStrategy;
}) => {
  const [dataUrl, setDataUrl] = useState<string | null>(null);

  useEffect(() => {
    requestIdleCallback(() => {
      setDataUrl(
        URL.createObjectURL(
          dataURLtoBlob(
            thumbHashToDataURL(base64ToUint8Array('a/cNG4L1NUOKhahX+XncHfg=')),
          ),
        ),
      );
    });
  }, []);

[evanw]

Data URLs are already URLs. You don't need to convert a data URL into an object URL to be able to use it. Doing that is slower, requires more code, and actually introduces a memory leak as URLs returned by URL.createObjectURL keep the blob alive until you call URL.revokeObjectURL. Instead, you can just use the data URL as the URL directly.

[lilouartz]

The reason I used object URLs is to workaround this issue https://stackoverflow.com/q/78645289/24982554

[lilouartz]

I am having a bit of a problem with this approach (of generating the image client-side).

It looks like the amount of time it takes to generate image makes the placeholder appear as a blank space for a long-time:

https://pillser.com/supplements/calcium-magnesium-zinc-with-vitamin-d3-2577

I even removed the URL.createObjectURL logic. It's now just:

  useEffect(() => {
    requestIdleCallback(() => {
      setDataUrl(
        thumbHashToDataURL(base64ToUint8Array('a/cNG4L1NUOKhahX+XncHfg=')),
      );
    });
  }, []);

[lilouartz]

I ended up moving image generation logic back to server-side. The load experience is far better despite the larger payload size.

[Green-Sky]

I ended up moving image generation logic back to server-side. The load experience is far better despite the larger payload size.

That's kinda sad. You can still try to reduce the image size and transfer a low res version, since the blur is somewhat forgiving in zoom blur. (also check out the other issue i linked)

[andupotorac]

@lilouartz this looks like something you need: https://github.com/evanw/thumbhash/issues/46.