[whatwg] responsive images

[Glenn Maynard]

On Tue, May 22, 2012 at 12:39 AM, Gábor Szabó <szabo.b.gabor at gmail.com>wrote:

> why don't we keep the current markup and use progressive images. this way
> the browser could decide what resolution he needs, and when to stop
> downloading. this would solve the problem
>

This doesn't work.  You can't stop a TCP download on a dime, due to TCP
windowing, and aborting a download kills pipelined transfers, which ruins
performance.  You'd need to know in advance how many bytes to download to
receive a given number of JPEG passes, which complicates things a lot;
you'd need to inline a pass count/byte range index, which creates a harsh
data dependency.

JPEG quality is also a different axis of quality than changing resolution;
if you want to drop the resolution by 1/2x or 1/4x, you often really do
want to use an image authored at a lower resolution rather than using a
lower-quality image, especially for non-photographic art like icons.  It
doesn't really work for PNG, either, since partial interlaced PNGs are too
low-quality to be of much practical use (at least JPEG gives a reasonable
quality--but no alpha).

-- 
Glenn Maynard