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Comment by archgrove | Hacker News Reader

That's fine if a) you're willing to maintain two image sets and, b) the only two resolution images you need are "normal" and "2 x normal". The advantage of a progressive quality system is it scales to arbitrary requirements in a single resource. One file provides 1x, 2x, 3x, 3.14x etc.

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Storage is too cheap to care these days.

When $110 buys you 2TB (this morning on Newegg), then doing it on the fly and caching the result has about 100x better ROI than trying to solve it with a smart format. Remember, we're speaking about still photos here, where high retina quality ones rarely take more than 500k each, so 2TB buys you room for 4,000,000 photos (and since you'll be caching the lower res 200K images, it actually buys you room for 10,000,000 million photos)

That's not the case for videos - netflix, hulu and friends have multiple copies of each 1GB optimized for different devices. On-the-fly conversion is not possible, and the stream are significantly difference. For them, a reasonable, universally supported progressive video format will indeed make a huge difference

I don't think archgrove's point was about storage, but about the extra friction of tracking N files instead of 1.

That might be, but with the right Apache, nginx, varnish (take your pick) module, this friction will be reduced to saying something like:

    lower_res {
      Request /lowres/*.jpg
      Provide /highres/$1.jpg
      Downscale 50%,50%
      Cached_on /mnt/cheapdisk_that_can_go_away_at_any_time
    }

I'm not aware of such an existing module, but I'm sure a good one will appear within the next couple of years of it does not yet exist.

Compared to developing and deploying a new progressive format (across users, web servers and web browsers), the effort -- both in developing this module, and in configuration, is negligible.

Problem with new formats is legacy support. Something that could degrade gracefully on browsers that don't add support would be very welcome. Maybe the best solution is to keep the current 'img' tag notation, but somehow indicate to browsers that double-rez assets are likely to be available at something like 'filename_x2.ext', and they should request those when they come across an img tag, instead of 'filename.ext', falling back with a second request for the latter in case the '_x2' isn't found. Something like:

  <meta img-x2-res="_x2" />

Encoding the image twice with a standardized addition to the filename is just an extra bit to add to the export macro. The image storage is irrelevant for most cases (assuming you compress appropriately); it's the bandwidth and request volume that's precious.

If you are going to do that you may as well have a meta tag to set a suffix "to find the jpeg2000 version of the image", and browsers that understand that format can then get the better format.

Not a bad idea. The meta tag should be made our bitch, so we don't have to work so much, and our sites can degrade gracefully.

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