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Why tiny JPEGs look different in Chrome
- PetitPrince 2mo agoSo is Firefox doing a full rendering then scaling, or is it also doing a partial rendering but in another way? You're only telling one side of the story.
- the8472 2mo agoFirefox doesn't decode the image into a full-resolution buffer and then downscale either, instead it does a streaming decode and applies downscaling on the fly. They call it downscale-during-decode[0]. I guess it doesn't do partial decoding of the 8x8 blocks though. [0] https://bugzilla.mozilla.org/show_bug.cgi?id=1045926 https://bugzilla.mozilla.org/show_bug.cgi?id=1045926
- deleted 2mo ago[deleted]
- gutechh 2mo agoAh! It took a fair bit of digging to get there. Maybe I'll look into the firefox pipeline and make another post. In the mean time if anyone know the internals and how firefox does it, I'm eager to hear about it!
- debazel 2mo agoChrome and Firefox uses two different scaling algorithms that is probably contributing a lot more to this difference. Chrome is more blurry in general while Firefox is sharper but has slightly more ringing artifacts. Personally I prefer the Firefox version.
- gutechh 2mo agoI do prefer the firefox look too! I'd be curious to hear your take on what could be the root cause of this. I'm far from a image rendering expert. But I remember when inspecting the edges and curves of the images in a DCT visualizer they were all in the AC coefficients which is what led me to the conclusion of the post.
- ack_complete 2mo agoI wonder if this is a gamma correction related. JPEG encodes directly in a non linear color encoding (full-range YCbCr), so the partial decoding may be effectively scaling without gamma correction.
- debazel 2mo agoI'm far from an image rendering expert myself, but I don't think there is a single root cause here. I don't doubt the partial decoding would affect the final result just as the scaling algorithm itself, so in the end it's going to be a combination of it all. The reason I believe the scaling algorithm is contributing more in your particular example, is because it looks almost exactly like a classic B/W comparison between a sharp ringing heavy algorithm and a more blurry one. For reference here is a quick comparison between Lanczos/Bilinear I threw together: https://twinlens.app/compare?share=40973d84a174 https://twinlens.app/compare?share=40973d84a174 It would be interesting to see how your example would look if you used colors instead, where the ringing artifacts become a lot more obvious. Like this one: https://twinlens.app/compare?share=8fb890a5820e https://twinlens.app/compare?share=8fb890a5820e
- gutechh 2mo agoThanks for these! Indeed I understand your point now. I'll add a little note on the post later today. Another interesting bit is that It wasn't so easy to get an image showing the issue a clear as we had it. My hunch is that moiré patterns might have a role in this, as most images where the the issue showed, had some kind of grid/repetition. I suppose some images might be more affected by the IDCT and other more affected by the scaling algorithm, making it more or less visible. It's a mix like you said!
- aidenn0 2mo agoI've noticed that a lot of objective measures of image quality prefer blur to ringing, but many subjective measurements tilt the other way.
- ryandamm 2mo agoThat's why you should prefer LPIPS to PSNR. LPIPS is a learned metric that uses subjective human input. That said, it's limited due to the training set, iirc. So we still use PSNR regularly — it's an easily-understood metric with widely-understood limitations, which is in practice not too bad. Devil you know, etc.
- m-schuetz 2mo agoIronically when we did compression quality evaluations, me and my colleague found that PSNR way better matches our perception of quality, than LPIPS or FLIP. Our assumption is that LPIPS is biased towards quality artifacts that is not representative of compression quality artifacts.
- hatthew 2mo agoIt depends on the target audience. Many people prefer the oversharpened content. I always find it incredible how so many people never change the oversharpened and oversaturated default settings on TVs.
- smallnix 2mo agoWould be nifty if they only did that partial scaling when there's little memory available.
- gutechh 2mo agoahah, yeah surprising considering how Chrome is RAM hungry, 20mb isn't that much of a win. On another end when trying to reproduce the glitch, it was quite hard! basically invisible on photos and not all icons were affected. So it does work very well. It was kind of our fault to use a jpg for an icon ahah.
- kristianp 2mo agoI assumed Chrome is memory hungry due to the JavaScript VM, but there's probably many optimisations that trade memory for speed. (Unlike this one).
- adzm 2mo agoIt's not a matter of memory but speed; the difference is drastic since memory is slow (well compared to cpu cache)
- muizelaar 2mo agoThe work for decompressing at a lower scale in Firefox is happening here: https://bugzilla.mozilla.org/show_bug.cgi?id=2033250 https://bugzilla.mozilla.org/show_bug.cgi?id=2033250
- gutechh 2mo agoThanks, I knew it was much more efficient, but seeing the numbers in the benchmarks make me appreciate this "trick" even more!
- adzm 2mo agoWow, this explains an issue I ran into for images from a certain vendor when we used idct scaling for the same reason: Some encoders (and a meaningful share of JPEGs in the wild) leave zeros or garbage in the unused rows/columns of the trailing MCU. At full-size decode those samples are cropped away, but IDCT scaling mixes them into neighboring output pixels and the artifacts become visible. See https://crbug.com/890745 https://crbug.com/890745 and https://github.com/libjpeg-turbo/libjpeg-turbo/issues/297 https://github.com/libjpeg-turbo/libjpeg-turbo/issues/297 In our particular case we were able to just crop out the edges and it was worth the tradeoff
- bluedino 2mo agoReminds me of digging into HTML Canvas scaling, especially when HiDPI Macs came out.
- jonathanlydall 2mo agoI'm pretty sure the same issue happens with PNGs, which being lossless are generally good for icons as they don't land up with compression artifacts like what happens in JPEGs (which the author points out are really for photographs), they also support alpha blending. When Chrome introduced this "optimization" and it made it through to an Electron release which we were upgrading to, it really messed up the icons in a lot of places in our product such that we had to hold off the upgrade until we had SVGs to replace them. SVGs also have the advantage of being able to respond to light/dark mode. We just needed to put each icon in its own shadow DOM to avoid styles clashing between the different SVGs if they happen to be named the same which was a bit of an annoyance for our graphic designer.
- StilesCrisis 2mo agoYou were using bitmap icons that were more than 8x larger on each axis than necessary? Why?
- aljgz 2mo agoGuess: same icon used in very small size for lists/menus and much larger when you select the item. Also, if the same one is used for all resolutions, the actual size can vary widely between monitor sizes, DPIs, resolutions, scales. Good to have one that looks decent to people who see it large and/or care about quality
- jonathanlydall 2mo agoPretty much. The icon appeared bigger in some places than others and wanted it to look decent on higher DPI displays. SVGs are so much better for this though, smaller in size and look great at pretty much any resolution.
- gutechh 2mo agoAh this is weird! My understanding is that png doesn't store the images like jpg at all, they use a palette of all the colors in the image. Then each pixel is a reference to this palette. So it's not IDCT scaling, but I imagine there are other tricks to save on space/cpu when decoding pngs.
- LoganDark 2mo agoNot sure why one would use JPEG for a little digital icon anyway. It is indeed only acceptable for photos. SVG is a good choice for icons, PNG or WebP for other digital content.
- gutechh 2mo agoYes! for a bit of backstory, it was an internal icon on a prototype that we were polishing up. So I get why the person did it at the time, running after the svg would have been too much effort for something that might have been tossed in the end.
- LoganDark 2mo agoI mean it's surprising someone would ever save a digital icon as JPG in the first place rather than something like PNG.
- kevin_thibedeau 2mo agoDigital natives are commonly unaware of how anything works.
- Theodores 2mo agoYou can over ride lib-jpeg-turbo with the moz-jpeg 'update' if you want much nicer jpeg things going on. Mozilla wringed out more from JPEG for Meta/Instagram about a decade or so ago, and their library would be noteworthy in this article, for comparison. The basic idea was that JPEG was devised when CPU cycles were expensive and displays were analogue, meaning that only a limited effort was made to optimise, resulting in things like banding, that OG CRTs handled well, unlike modern digital displays (on systems with 1000000 more CPU). Regardless of what tools you are using, going from 'gigapixels' to a thumbnail is going to be a two or more step process, with a colourful item rendered a grey mush, when you really needed some of the colours in the original. Few respect the pixel blocks of JPEG (8 x 8) and most graphic artists have no knowledge of the powers of two. Once upon a time it was necessary to align image dimensions with important binary numbers, particularly if working with texture maps for early 3D graphics. The other thing going on in the article is that practically every web screen should be considered 'retina' resolution, with everything apart from the lamest office PC having a pixel resolution equivalent to 1.5x the amount of pixels shown 'nominally'. If the web stats say '1280 x 720' as a oft-used resolution, regardless of device, that will be a 1920 x 1080 screen at 1.5x, with Chrome and other browsers packing in 1920 rather than 1280 pixels across, if the image has the pixels in it for that.
- hnv9j3vudy 2mo ago[dead]
- iknowstuff 2mo agoThoroughly enjoyed reading this! In other news, AVIF is at 95%: https://caniuse.com/avif https://caniuse.com/avif so it's probably time to give it the first preference over jpg.
- adzm 2mo agoInteresting, I don't seem to see options for this in avifenc for example, I suppose this needs fancier interaction with the library directly
- gutechh 2mo agoThank you! I wonder if we'll ever see avif/webp takeover or if it's gonna be like ipv4/ipv6.
- theandrewbailey 2mo agoI've primarily been using AVIF with JPG as fallback on my blog for a few years. The efficiency gain is wild. I wonder if AV2 will be integrated into AVIF at some point (AVIF is based on AV1).
- tosti 2mo agoThe matrix of sources for a large picture can be mind boggling huge. We have jpeg, webp, avif and jpegxl. Portrait orientation and landscape. 3 or 4 different pixel ratios and of course, different screen resolutions. Dark mode support doubles all of that work. Hardly anyone is going to do all of this correctly, automated or not.
- advisedwang 2mo ago> Really, the moral here is that you should not use JPEG for icons and the like And, more importantly, you should use images that are an appropriate resolution for the size they will be displayed. Even if you switch to PNG, using a 2000x2000 image for a icon displayed 20x20 is a waste.
- ryandrake 2mo ago> using a 2000x2000 image for a icon displayed 20x20 is a waste The number of web sites that do this is enraging.
- AlienRobot 2mo agoSome websites even do this for the favicon.
- decimalenough 2mo agoThe favicon spec is a mess these days. The OG was 16x16 pixels, but now you're supposed to provide a whole slew of resolutions up to 192x192 and you can do SVG as well. And browsers have no consistency in how they pick the one to actually display. https://en.wikipedia.org/wiki/Favicon#How_to_use https://en.wikipedia.org/wiki/Favicon#How_to_use
- notenlish 2mo agoWhy not use https://realfavicongenerator.net/ https://realfavicongenerator.net/
- notRobot 2mo agoIn my experience it works essentially everywhere to have a single png that's ~256*256px as a linked favicon, perhaps with a single .ico fallback.
- reddalo 2mo ago> browsers have no consistency in how they pick the one to actually display The same Firefox on macOS shows different favicons depending on if I'm using it on the laptop screen or an external one (probably because of different pixel densities). It's crazy!
- altairprime 2mo ago15px suggests that using an ICO file, horrifying as that sounds, might be a very successful solution here. Yes, I know PNG and GIF would also work, but if ICO format is still support for favicons at multiple resolutions with clean scaling, then wouldn’t it be support for doc images as well?
- kccqzy 2mo agoIf you care about the rendered quality, you should never use the browser itself to downscale images. Browsers don’t consistently use the state-of-the-art algorithm for downscaling, which is Lanczos 3-lobe. This is independent of partial IDCT. Browsers generally favor performance. And the algorithm chosen could even depend on the specific GPU in use. That said if you are using the web to develop UI, it’s accepted that different browsers and users get slightly different renderings, unless you write your own image renderer with canvas. If you do care that much you should probably write native code.
- qdotme 2mo agoI'm actually curious if nowadays some ML-based algorithms are not beating Lanczos 3-lobe to it - at least in perceptual quality of the downscale. The have /long/ surpassed it in upscaling.
- Matumio 2mo agoAlso the pixels were probably downscaled in sRGB gamma by JPEG instead of linear light, so the overall brightness will be wrong anyway, if there was lots of high-frequency content in the original.
- edflsafoiewq 2mo agoThe DCs giving you a 1/8 downscale is well known, but the interesting part to me was this generalizes so you can get 1/4 (resp. 1/2) downscales by using only the 2x2 (resp. 4x4) block of LF coefficients.
- qdotme 2mo agoThis is even more interesting (full disclosure - I vibecoded a lib for it lately - lowzag) when you take into consideration working set restrictions. In almost every case, downscaling-while-decoding is going to beat decode-then-scale on performance - merely keeping the uncompressed image in RAM is going to cost you, when you can scale it down in L1 or even vector registers.
- gwittel 2mo agoSometimes you can control this with the “image-rendering” CSS attribute. It lets you control the scaling algorithm used. Different browsers seem to choose the algorithm in different ways. Came across this when an image looked different between two browsers, but only on high DPI monitors.
- scotty79 2mo agoPeople who usually complain about AI write ups apparently aren't interested in this topic.
- talon8635 2mo agoI had a hell of a time rendering svg to print sanely in chrome, no issues in ff
- linzhangrun 2mo agoCould this be related to the GPU? I remember that sites like Reddit use subtle differences in GPU rendering to fingerprint devices.
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- baby6343 2mo ago[flagged]