How convert transparent and black (and maybe in beetween values) to white->black sameway?

[MxHeppa]

How convert transparent and black (and maybe in beetween values) to white->black sameway? in affinity photo or designer.

[MxHeppa]

and i man easier way than making new white document where i cut and paste this transparent background image. easier for exmaple way keeps dimensions i dont need copy original image size by hand. i bet there should be way do this. related i hand drawed with Wacom one photo get guide lines one picture.

[Fixx]

Would just making background white instead of transparent do what you need? File > Document setup > Colour > Transparent background <off>.