How to Feather Edge of Graphic in a Circle?

[TechnicGeek]

Hello,

I have a graphic in a circle and I want to have it's edge feathered in order to fit it inside mockup.
it must look as if it is not just laid over it but kind of part of mockup.

To give a better idea of what I am looking for, here is an image of a cellphone laying on the ground
where ground has sort of vignette effect. The farther it goes from center, the less it is visible:

   

I don't know whether it's vignette or blue that I need but I hope picture shows it.
I need it on a transparent background and not white since I want to integrate it
inside a mockup.

Actually vignette would make my image dark I think so maybe it's some kind of
special blur that I need?

Thanks.

[rich2005]

Different ways:

Give the image an alpha-channel Layer -> Transparency -> Add Alpha Channel
Make a circular selection then invert it. Select -> Invert
Big feather on the selection Select -> Feather
Cut the selection Edit -> Cut.

screenshots https://i.imgur.com/cfwHyc8.jpg

My preference is a layer mask
Add a white layer mask Layer -> Mask -> Add layer mask.
Use a white-to-black circular gradient in the layer mask

screenshots: https://i.imgur.com/7A5MT8y.jpg

[Ofnuts]

The big advantage of the layer mask is that by applying the Brightness-Contrast, Levels, or Curves tools you can adjust the opacity gradient very finely (where it starts, how steep it is....).