How to implement fixed layer blur on scroll?

Question

Apache HTTP Server

Once upon a time, I downloaded an application for ios, it was not very good in itself, but I liked one feature in it. Example:

I want to implement something similar, I've been trying for 2 months now and nothing comes out, then there's a jamb here and there ...
So I decided to turn to experts for the first time for help. Poke
template In theory, you need to somehow blur what goes under the header layer. I achieved something similar with the help of a translucent picture and a gradient, the picture is something like frosted glass. But the effect is not the same, but only similar + a picture of this quality weighed about 1mb. Maybe someone has a js script that blurs everything that falls into the frame?
I climbed a lot where, I know that css is not capable of this, if you don’t pervert and do 4 layers each .. It’s better to turn to js. I also know that c++ is able to do something similar, but c++ won't work in browsers.
Do not send here

Answer 1

Redirect 301 a.site.ru a.site.ru/blog

Answer 2

nbartlomiej.github.io/foggy