Why Tiny JPEGs Look Different in Chrome

(guillaumetech.github.io)

76 points | by gutechh an hour ago ago

11 comments

  • muizelaar 22 minutes ago

    The work for decompressing at a lower scale in Firefox is happening here: https://bugzilla.mozilla.org/show_bug.cgi?id=2033250

  • debazel 32 minutes ago

    Chrome 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 23 minutes ago

      I 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.

    • aidenn0 19 minutes ago

      I've noticed that a lot of objective measures of image quality prefer blur to ringing, but many subjective measurements tilt the other way.

      • ryandamm 10 minutes ago

        That'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.

  • bluedino 10 minutes ago

    Reminds me of digging into HTML Canvas scaling, especially when HiDPI Macs came out.

  • PetitPrince 36 minutes ago

    So 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 31 minutes ago

      Firefox 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

    • gutechh 20 minutes ago

      Ah! 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!

  • smallnix 28 minutes ago

    Would be nifty if they only did that partial scaling when there's little memory available.

    • gutechh 16 minutes ago

      ahah, 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.