Why decoded blurhash is so big?

[rabinpoudyal]

I tried to create a blurhash from 50x50 image and tried decoding it into base64. I got very lengthly string as output (400-2000):
/9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAFA3PEY8MlBGQUZaVVBfeMiCeG5uePWvuZHI////////////////////////////////////////////////////2wBDAVVaWnhpeOuCguv/////////////////////////////////////////////////////////////////////////wAARCAAgACADAREAAhEBAxEB/8QAFwABAQEBAAAAAAAAAAAAAAAAAQMCBP/EABgQAQEBAQEAAAAAAAAAAAAAAAEAAhES/8QAFgEBAQEAAAAAAAAAAAAAAAAAAAEC/8QAFREBAQAAAAAAAAAAAAAAAAAAAAH/2gAMAwEAAhEDEQA/AM5YioxQtRntESzZiqjUC1GFoihiNHzAJBhzRHSFpSkE9EByg//Z

Is there any way to shorten this string? It seems airbnb also has similar blurhash implementation but they have only 179character long encoded base64 string for images. I am trying to decode in server since the page has lot of images and not feasible to decode in client side.

[predaytor]

Not sure why it takes such long string in your example, I'm using sharp with 16px sizes, blur 4px, and you should pick lossless for better compression (great quality, less artifacts).

export async function resolveBlurhashURI(hash: string, width = 16, height = 16, punch = 1) {
	if (!isBlurhashValid(hash)) throw Error('invalid hash');

	const pixels = decode(hash, width, height, punch);

	const resizedImageBuffer = await sharp(Buffer.from(pixels), {
		raw: {
			channels: 4,
			width,
			height,
		},
	})
		.webp({
			lossless: true,
			smartSubsample: true,
			quality: 100,
		})
                .blur(4)
		.toBuffer();

	return `data:image/webp;base64,${resizedImageBuffer.toString('base64')}`;
}

[ahmadkhalaf1]

Not sure why it takes such long string in your example, I'm using sharp with 16px sizes, blur 4px, and you should pick lossless for better compression (great quality, less artifacts).

export async function resolveBlurhashURI(hash: string, width = 16, height = 16, punch = 1) {
	if (!isBlurhashValid(hash)) throw Error('invalid hash');

	const pixels = decode(hash, width, height, punch);

	const resizedImageBuffer = await sharp(Buffer.from(pixels), {
		raw: {
			channels: 4,
			width,
			height,
		},
	})
		.webp({
			lossless: true,
			smartSubsample: true,
			quality: 100,
		})
                .blur(4)
		.toBuffer();

	return `data:image/webp;base64,${resizedImageBuffer.toString('base64')}`;
}

Can i use this with nodejs ? can you please show an example how would this function work ?
can i pass an image url and it will hash it for me + sharp optimization ?
where does decode function comes from?

Thanks

[DagAgren]

That is missing the point of the blurhash entirely. It is designed exactly as a format to send over the wire to the client. If you are not doing that, you do not need blurhash at all.