Comment by maria2 | Hacker News Reader

Comment by maria2 | Hacker News Reader

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> I don't know what you mean by "unlocking anything new". You have identical images at a smaller size.

Yes exactly, nothing new is unlocked. So why would I use this format? Was the old size of the images preventing me from enjoying them in any way? No. Of all the old JPEGs out there that absolutely must be losslessly transcoded from the already lossy JPEG encoding, how many are prohibitively large? You can still look at both a JPEG and JPEG XL image locally. Most likely you'd be able to serve both images over HTTP, although the JPEG image may take a bit longer to load. And how many cases require the new and old images be exactly the same? My point is that, if the main selling point of your codec is that you can create the same thing as 30 years ago only smaller, then it's going to be a hard sell compared to other formats out there. If the choice was between JPEG and JPEG XL, then sure, let's use JPEG XL. But the choice is between JPEG XL and other formats with better features.

Other image formats like AVIF add new features that enhance images. Yes, the images are smaller, but also way more powerful. Image sequences, for instance, enable new features like "live images." Converting your old JPEG to a smaller JPEG isn't going to magically enable live images.

tldr: I'm looking for a reason to care that I can losslessly re-transcode my old JPEGs. Ok, the re-transcoded images are smaller and exactly the same as before, but what is a real world reason why I would need that vs. using the old JPEG directly or re-transcoding it to AVIF?

> So why would I use this format?

Because the size is smaller and the quality is the same? Literally the same reason why you'd use any new image format, except that this benefit also applies to existing images, not just new ones?

I'm not against AVIF or anything, if you want to add future images which are using fancy animation features from AVIF then that's cool. You don't have to choose between image formats, you can (and already do!) use the right one for the task.

> tldr: I'm looking for a reason to care that I can losslessly re-transcode my old JPEGs. Ok, the re-transcoded images are smaller and exactly the same as before, but what is a real world reason why I would need that vs. using the old JPEG directly or re-transcoding it to AVIF?

You can use the old JPEG directly, but then your library takes up more space. If you re-transcode your old JPEGs to AVIF, you're losing quality or at the very least irreversibly changing the images.

I'm not arguing that it's the world's biggest deal or anything, but a free 20% size reduction on all photos in an image library and all JPEGs sent over the web doesn't seem like a bad deal.

I think the point is that it is much more important to achieve better compression ratios on the monstrously large files modern digital cameras produce than to reduce the already tiny sizes of peoples' family albums from the 90's. Compressing a 90 kb to 45 kb without loss of quality is impressive, but not as useful as compressing a 20 mb raw image to 18 mb.

My JPEGs are significantly larger than 90kB. At this point you're just trolling.

I think you're not understanding my question. You said that the most exciting feature of JPEG XL is the ability to losslessly encode old JPEGs. My point is that, if this is the most exciting feature, then it's unsurprising that the industry is choosing to ignore JPEG XL as the "most exciting feature" is more or less useless.

Technology is a means to an end. Transcoding images is a means. The end is what you do with it. In the 90s and early 2000s, encoding images in JPEG allowed for digital cameras to store vastly more images on their limited storage space. Bandwidth was extremely limited, so JPEG encoding allowed for detailed images to be shared over the web, which wouldn't have been possible in a different format. Today, however, storage and bandwidth are cheap. JPEG already does a decent enough job for old images. Making old images even smaller isn't really enabling any new "ends."

I guess the ultimate question I'm asking is "Why do you want your old JPEGs to be smaller?" What is the end you hope to achieve with smaller JPEGs?

Smaller is what compression is for.

And there are other codecs that compress similarly to JPEG XL that also support other features like animation. So, again, why would I use JPEG XL?

But anyway, this conversation was helpful. I guess there aren't really many reasons to use JPEG XL.

There are no such similar codecs. Jpeg xl is in its own category in compression efficiency when rated by users at densities/qualities used in the internet. Roughly similar efficiency steps between libjpeg-turbo, WebP, AVIF and then jpeg xl.

JXL has the feature set that is better than any other solution.

Killer feature #1 is compressing existing JPEG images. Nothing else can do this

Killer feature #2 is HDR images with over 10 bits of depth and high resolution. It comes out of your camera/phone already like this but we can't post it online! What a joke

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