How to create proper size drawable on android as it was designed on px image - knowing dimensions,density, etc.?

I would really know how to create proper drawables for android mobile phones. According to lessons from udacity "Android Design for Developers".

Aim: create identical size drawable on screen as it was designed on image. What do I know:

1. screens size 1440x2560 px

2. density is 560 dpi - which is xxxhdpi
3. so, screen in dp dimensions is 411x731 dp
4. icon is 158x158 px
5. I know I should put this in xxxhdpi folder.

Should I scale down whole image to dp dimensions (411x731 px) and then design 150x150px "man" to keep the same size in android screen as it was created on image? How could I mange it? So far I use to create "lucky size of image" to get proper size or I was defining custom size in code. But this not the clue. Help.

PS. please do not reffer to supporting screens android page because I were there.

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I do not know what px size should have "man" picture for xxxhdpi to get the same size as is on image after taking screenshot.

See. You image dimensions for xxxhdpi is 158x158 px.

Let's take mdpi as 1x. then, hdpi = 1.5x xhdpi = 2x xxhdpi = 3x xxxhdpi = 4x

4x = 158x158 (let's add some margin and make it 160x160)
1x = 40x40
1.5x = 60x60
2x = 80x80
3x = 120x120
4x = 160x160