Gradients antialias use low color or blends depending on current pattern

[madmax]

Try something like

FillRect(BRect(0,0, 1,1), pattern);
SetLowColor(0, 255, 0);
FillEllipse(rect, gradient);

If pattern is B_SOLID_LOW or the default B_SOLID_HIGH, the circle blends beautifully with its background. For any other pattern, say B_MIXED_COLORS, the low color is used instead and you get a green ring.

[korli]

Fixed in hrev56993