Perceptual Image Compression at Flickr • Hacker News Board

Re: Perceptual Image Compression at Flickr

#11

Post by moneylotion » Mon, Sep 28, 2015, 11:52 AM UTC

does netflix do this too? or does netflix just get like insane raw source files?

Re: Perceptual Image Compression at Flickr

#12

Post by fahimulhaq » Mon, Sep 28, 2015, 12:04 PM UTC

__alexs wrote: post #3

> 15% fewer bytes per image makes for a much more responsive experience. I wonder how they measured this. Seems like perceived speed gains would be sub-linear with file sizes to me. Particularly as actual transfer speed is often too once you factor in network latency patterns.

Irony is that this additional 15% compression was noticed by users - not because of improved responsiveness or load times but because it degraded image quality to such a level that users noticed it.

Re: Perceptual Image Compression at Flickr

#13

Post by cyberjunkie » Mon, Sep 28, 2015, 12:05 PM UTC

I've been using Flickr for a while now, and am a regular visitor to flickr.com/explore. It has always been so painfully slow to load. Moving to the final photo page is even bigger a task. Sometimes, the thumbnails take two minutes to load, but if I get a direct link to the 4MB image, it downloads in literally 5-10 seconds.

I'm waiting to get home to see if they've done to fix this mess.

Re: Perceptual Image Compression at Flickr

#14

Post by manaskarekar » Mon, Sep 28, 2015, 12:36 PM UTC

This is all impressive and all, but flickr needs to improve their page load times, a lot. I like flickr a lot, and as a paying customer, I'm tempted by 500px every time I visit them.

Re: Perceptual Image Compression at Flickr

#15

Post by codementum » Mon, Sep 28, 2015, 12:42 PM UTC

IshKebab wrote: post #10

TazeTSchnitzel wrote: post #7

Okay, but how is this "perceptual image compression" done?

> Technology exists that attempts to do this Clearly.

It's odd that this is missing. Without it, it's not possible to analyze for biases w.r.t. the stimuli used or even the perceptual features they're adjusting.

Re: Perceptual Image Compression at Flickr

#16

Post by fsiefken » Mon, Sep 28, 2015, 12:49 PM UTC

Does anyone know what the equivalent imagemagick convert command could be for jpeg and webp? If Firefox supports webp in the near future and IE and Safari support can be done through javascript decompression what could the size reduction with a similar process on webp be compared to jpeg be?

Re: Perceptual Image Compression at Flickr

#17

Post by 1ris » Mon, Sep 28, 2015, 1:08 PM UTC

fsiefken wrote: post #16

Does anyone know what the equivalent imagemagick convert command could be for jpeg and webp? If Firefox supports webp in the near future and IE and Safari support can be done through javascript decompression what could the size reduction with a similar process on webp be compared to jpeg be?

Imagemagick supports webp, and that since quite a while. I currently use the prepackaged Ubuntu version on my desktop, ImageMagick 6.7.7-10 2014-03-06 Q16 which supports it.

Re: Perceptual Image Compression at Flickr

#18

Post by cbr » Mon, Sep 28, 2015, 1:20 PM UTC

I read this looking to see if there was anything we could adapt for mod_pagespeed. Making images smaller without looking worse is, of course, what anyone optimizing images wants. Unfortunately, all they say about how they actually did their perceptual compression is:

    Ideally we’d have an algorithm which automatically tuned
    all JPEG parameters to make a file smaller, but which
    would limit perceptible changes to the image.  Technology
    exists that attempts to do this and can decrease image
    file size by 30-50%.

As far as I know, the only practical way to do this is to do a binary search for the quality level that gives a desired SSIM [1], but this is kind of expensive and I was hoping that they had something cool to tell us here.

[1] If you're interested in getting this kind of improvement and your images are viewed enough that it's worth doing more intensive encoding to get things exactly right, you could do this:

    def evaluator(image, candidate_quality):
      compressed = jpeg_compress(image, candidate_quality)
      return dssim(image, compressed)

    best_quality = binary_search(
      image, desired_dssim, candidate_qualities, evaluator)

Re: Perceptual Image Compression at Flickr

#19

Post by simonswords82 » Mon, Sep 28, 2015, 1:21 PM UTC

cyberjunkie wrote: post #13

I've been using Flickr for a while now, and am a regular visitor to flickr.com/explore. It has always been so painfully slow to load. Moving to the final photo page is even bigger a task. Sometimes, the thumbnails take two minutes to load, but if I get a direct link to the 4MB image, it downloads in literally 5-10 seconds. I'm waiting to get home to see if they've done to fix this mess.

Totally agree. When I'm on Reddit and I spot the link is to flickr.com (rather than say imgur.com) I'll usually skip the link and move to the next post as I know the Flickr photo will take longer than I'm willing to wait.

Re: Perceptual Image Compression at Flickr

#20

Post by cbr » Mon, Sep 28, 2015, 1:23 PM UTC

fsiefken wrote: post #16

Does anyone know what the equivalent imagemagick convert command could be for jpeg and webp? If Firefox supports webp in the near future and IE and Safari support can be done through javascript decompression what could the size reduction with a similar process on webp be compared to jpeg be?

    If Firefox supports webp in the near future...

Where are you getting this? My understanding is FF still doesn't intend to add WebP support. https://bugzilla.mozilla.org/show_bug.cgi?id=856375