D18377: Update blur to be more natural

ngraham added a comment.


  In D18377#398748 <https://phabricator.kde.org/D18377#398748>, @zzag wrote:
  
  > I personally think the blur effect is good enough already.
  
  
  It's definitely good already, but as the "before" screenshots point out, it suffers from a well-known and common problem that the area between two blurred color appears too dark with many blur implementations. This is a bug, and fixing it is basically a bugfix.
  
  > Also, I'd like to point out that an option to enable/disable the "accurate" blur is a no-go.
  
  I agree that an option is undesirable.

REPOSITORY
  R108 KWin

REVISION DETAIL
  https://phabricator.kde.org/D18377

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