Use alpha channel in brush tips, or add an overlay tip

[Rigognos]

@Voronwe13

I did some more work on the Lightness brush in the smudge engine. I have it mostly working now.

If this lightness feature has been implemented for the smudge brush engine, I wonder how well it will work with the smear alpha toggle switch being developed separately.

Selective Color Channel Blending for Smudge Brush

Hi, @Rigognos and @RamonM! Could you please test this package? Now there is “Smear Alpha” checkbox in “Smudge Rate” option that should be unchecked to get the effect you need.

This other smuge brush feature might still need some work before it can work with the brush lightness settings, but hopefully it will be able to work in the end.