Technical data

Getting Started 11
On top of the Background layer, you can create any number of new
layers in your image. Each new one appears on top of another,
comprising a stack of layers that you can view and manipulate with the
Layer Manager tab. We call these additional layers standard layers to
differentiate them from the Background layer. Standard layers behave
like transparent sheets through which the underlying layers are visible.
There’s a third kind of layer, called a text layer (see Chapter 4), which
resembles a standard transparent layer but can only contain text. Text
layers keep blocks of text editable so you can go back and change the
font or retype characters.
With few exceptions, you will work on just one layer at any given time,
clicking in the Layer Manager tab to select the current or active layer.
Selections (see above) and layers are related concepts. Whenever there’s
a selection, certain tools and commands operate only on the pixels inside
the selection—as opposed to a condition where nothing is selected, in
which case those functions generally affect the entire active layer.
If your image has multiple layers, and you switch to another layer, the
selection doesn’t stay on the previous layer—it follows you to the new
active layer. This makes sense when you realize that the selection doesn’t
actually include image content—it just describes a region with
boundaries. And following the old advice “Don’t confuse the map with
the territory,” you can think of the selection as a kind of outline map, and
the active layer as the territory.
We’ll first encounter layers later in this chapter. Chapter 5 provides in-
depth coverage.
6 Opacity and transparency
Opacity and transparency are complementary—
two sides of the same coin. They both refer to the
degree to which a particular pixel’s color
contributes to the overall color at that point in the
image. (Pixels again are the “screen dots” that comprise a bitmap image
in PhotoPlus.) Varying opacity is rather like lighting a stage backdrop
(scrim) in a theater: depending on how you light the fine gauze sheet,
you can render the backdrop either visible or invisible. Fully opaque
pixels contribute their full color value to the image. Fully transparent
pixels are invisible: they contribute nothing to the image.