
I have small problem, advice please

I found here in the forum that it is possible to use eye drop to set colors for a pot ot brush.
What I need is to make gradient of two hexadecimally defined colors.
Example: I have web page with some background color. I want gradient on the image which dissolves in the background color. Usually gradient is short - up to half of the page and the rest is background color defined by HTML
Is it possible to define this in some way? May be arithmetic formula ...?