Correct math to blend color in the blur effect
Summary:
Signed-off-by: André Agenor <andreagenor@icloud.com>
This is the old way blur effect work
Now we have better blend colors
Reviewers: tcanabrava, patrickelectric
Reviewed By: tcanabrava
Tags: KDE Applications
Differential Revision: https://phabricator.kde.org/D20036