no support for pixel density descriptor (e.g. 2x)?

[larsbo]

When a srcset image is specified with a pixel density descriptor instead of a width descriptor as explained here:
https://webkit.org/blog/2910/improved-support-for-high-resolution-displays-with-the-srcset-image-attribute/
or more detailed in the official spec:
https://html.spec.whatwg.org/multipage/embedded-content.html#width-descriptor
the higher resolution image will be removed from srcset.

For example something like this

<img class="responsively-lazy" [...] data-srcset="image/3945799cca93f17f_280x280.jpg, image/3945799cca93f17f_280x280@2x.jpg 2x">

will be transformed into this

<img class="responsively-lazy" [...] srcset="image/3945799cca93f17f_280x280.jpg">

[ivopetkov]

That's true. Instead, the library takes pixel density into account.
Here is an example:
< ... data-srcset="images/400.jpg 400w, images/800.jpg 800w, images/1000.jpg 1000w" ... >
If the image is viewed on 2x device and the image width is 400px, then the 800w version will be loaded (2x400=800). If the device is 2.5x then the 1000w version will be loaded (2.5x400=1000).
This makes describing images much easier.

[larsbo]

What about a situation where you don't know images sizes, container widths etc. and you have only two image versions - a small one and a 2x-version and just want to automatically display the large one at high density displays?
For this case the other spec definition would make more sense.