I’ve got this shading test pattern made of multiple bitmaps on the same layer. I’ve got Fill All Shapes At Once selected, but it’s rastering them one by one, painfully slow.
Tried Grouping them, no difference. Tried “Fill Groups Together”, still rastering independently.
Grayscale isn’t supported by the code that does image compositing. There is no functional difference between what you’re doing here and just using filled rectangles with Power Scale values applied.
It goes through a completely different path in the code internally, because it’s not just on/off spans, but has additional information (intensity) tagging along.