PhotoPlus X2 User Guide - Serif

Painting and Drawing 87
On standard and Background layers, the tool
creates a "spectrum" effect, filling the active layer
or selection with colours spreading between the
current foreground and background colours. The
fill is applied rather like a coat of spray paint over
existing pixels on the layer; colour and
transparency properties in the fill gradient interact
with the existing pixels to produce new values. In
other words, once you've applied the fill, you can't
go back and edit it (except by undoing it and
trying again).
Transparency works in a comparable way, affecting how much the paint you apply
is "thinned." At full opacity, the fill completely obscures pixels underneath.
On text and shape layers, the Gradient Fill Tool
is even more powerful—the fill’s colour and
transparency properties remain editable.
Technically, the fill is a property of the layer, and
the shape(s) act as a "window" enabling you to see
the fill. Thus a single fill applies to all the shapes
on a particular layer—note the gradient fill
opposite which is applied across three
QuickShapes present on the same layer.
Transparency gradients determines which portions of the object you can see
through. Note that the Flood Fill Tool doesn't work with text or shapes. When first
drawn, a shape takes a Solid fill using the foreground colour. You can change the
fill type as described below.