`compress` middleware gzips images

[jazoom]

What version of Hono are you using?

4.5.5

What runtime/platform is your app running on?

Bun

What steps can reproduce the bug?

Use the middleware as intended

app.use(compress())

What is the expected behavior?

Only compress response types that benefit from compression.

What do you see instead?

Images and other non-compressible types are gzip encoded. This wastes CPU for no reason, and often actually results in larger response sizes.

Additional information

No response

[jazoom]

Perhaps the middleware needs something along these lines?

        const contentType = c.res.headers.get("Content-Type");
	if (!contentType) {
		return;
	}

	const isCompressible =
		contentType.includes("text/") ||
		contentType.includes("application/json") ||
		contentType.includes("application/javascript") ||
		contentType.includes("application/xml");

	if (!isCompressible) {
		return;
	}

[jazoom]

It might also be worth having a content size below which compression is not applied.

[akku1139]

How about specifying the Content-Type for compression in the middleware options?

interface CompressionOptions {
  encoding?: (typeof ENCODING_TYPES)[number],
  contentType?: Array<string>
}

[jazoom]

Cloudflare has a list here which may be a good default

https://developers.cloudflare.com/speed/optimization/content/brotli/content-compression

[jazoom]

Being able to set it as an option also sounds like a great idea.

[yusukebe]

Hi @jazoom @akku1139

This is an interesting issue. We can consider the API and implementation. Anyway, it's an enhancement rather than not a bug. I've changed the label.

[yusukebe]

Now, we can close this issue. Thanks.