change padding according to zoom setting

Dear helping angels,

is there a way to adjust the padding (that I use in the background image of my header) to different zoom settings? The padding changes the height of my header and therefore the height of my background image, and I would like the height to look the same on the screen irrespective of users zoom settings…

It seems a very basic question, but still I did not find anything on the web for that, though I tried a number of different keywords.

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