Making a precise blurry border

[Espermaschine]

Finished my season's greetings image yesterday and the thing i surprisingly struggled the most with was getting the vignette/blurry outline right.

Lets say i want something like this:

   

and i want perfect control over every detail of my blurry border. I want a certain area to be opaque, the rest blurry and i want to perfectly control how far the blurry region reaches.
How would you do this ?

Shrinking and feathering doesnt give me very predictable results....

I tried to solve the problem by reversing the approach:
shrunk a selection, inverted, activated the quick mask then blurred and manipulated with the curves tool.
Its still not the perfect solution.

   






Stars on transparent background for examples.
   

[Ofnuts]

Fir this kind of adjustments, I would use a layer mask filled with a "shaped" gradient:

   

and then use Curves. For the perfectionnist who has hoarded my script repositories, you can also generate this kind of mask (initially as a layer) with path to shape (two rounded squares, outer and inner), path-inbetweener (20 paths) and stroke-or-fill-visible-paths using a gradient. Then use as above with curves.

   

Same mask, different curves:

   

   

[Espermaschine]

I like the method with the square gradient !
The bevelled corners can be smoothed out with Gaussian Blur.

   

Maybe its also possible to layer several copies of the same blur and "compress" them to various levels...

Is Gaussian Blur a pixel value ?
I mean if i blur by 30, does that mean the blur goes 30pixels ?
It seems its twice that value.

(12-03-2017, 10:50 PM)Ofnuts Wrote: and then use Curves. For the perfectionnist who has hoarded my script repositories, you can also generate this kind of mask (initially as a layer) with path to shape (two rounded squares, outer and inner), path-inbetweener (20 paths) and stroke-or-fill-visible-paths using a gradient. Then use as above with curves.

This is also quite nice ! Here i used 8 intermediate paths and blurred the result a bit.

Does the ratio of the colours in the gradient affect the way the paths are stroked ?

   

[Ofnuts]

(12-03-2017, 11:37 PM)Espermaschine Wrote: Does the ratio of the colours in the gradient affect the way the paths are stroked ?

If you have 20 paths (the script samples the gradient on 20 equidistant values (including the ends) and strokes each path with the corresponding value.