This is the layers window or, palette, which shows the information about the layers in a particular image, and from which you can make changes (pressing the L-key will turn this palette on/off). You may also use the Layers item up on the menu bar, as well. Each image can be composed of a number of different sorts of layers. Generally, layers are just what is suggested by the word. Imagine transparencies stacked up on one another, contributing to the overall slide image, for example. Some transparencies, though, might let through only certain colors. Another might tend to darken all those underneath. Others might have things on them that other transparencies can't, due to processing methods. And so on. But the idea is to build up the image, from pieces which can be rearranged, changed, added, removed, because they are each separate layers.

There are three buttons, top right, on this layers window - called the layer tabs. As shown in the picture, above, the blend or, appearance, settings are normally shown (displayed with the leftmost tab). Here it shows that some image has four layers -

Background:

The base, or background, layer is what one would have without layering - just the dot/raster image, itself. If the program had no layering, as previous versions did not, then this is what you'd have - a 'background'. The background is like a background in animation drawing. It's goes down first, as it were, and the cels are placed on top for the characters, other trees, or something. You don't need to have a background when creating a layered image. But if you combine the entire result into a bitmap, it will 'fall down' to the background. And some tools only work on the background, not on layers.

Raster:

Like the background, any number of layers can be bit-mapped images. You can use blending into other layers, unlike with the background. That is, a layer can have a transparent section - a background wouldn't. And a mask can also associated with the image on that layer (the background can have a mask, too). In addition, some tools only work on layers, not the background.

Vector:

A layer reserved just for vector, point to point, graphics. No dots or image information. Just line drawings, vector points.

Adjustment:

Used to modify layers underneath - darkening them all, letting some color through, not others, and so on.

Looking on the left side of the palette, or window, you can type in any name you want for a layer, and that's supposed to be suggested, as well, in the picture. On the background, some tools, like scratch, will in fact only work on the background. Again, you don't need a background. But that's where everything ends up if you combine all the layers. And the raster layers are like the background in that they are bitmaps. Bitmaps can have masks associated with them, on that layer. That's what the little face or mask icon indicates. In fact, in this example above, you can see that both the vector and the raster layer have masks associated with them. The adjustment layer lets through or keeps back brightness, or colors, or something, associated with all dots in the images underneath. So in a way it, itself, is a 'mask', and you don't use masks with the adjustment layers. Of course the color icons at the far left identify the sort of layer it is, whatever name you give to the layer. And the eyeglasses buttons switch each layer on and off, in case you don't want to see them all at once, which is most of the time.

Back on the right half, under the tabs, it shows these "100" values and a grayscale gradient bar. That is a slider you can use for each of the layers to set the amount of fading, or blending. For example, say "a raster layer", in this example, contains some large gray text. You could fade left to 40 or 50, or whatever, on that layer, for a much lighter gray, even with some of the background showing through - just for effect. It's called the "layer opacity". And the way in which it is blended with underlying layers is determined by the blend mode you select, there. These are the same 17 blend modes used with Flood fill, by the way.

When you press the mask tab, at the left it simply shows whether or not you are using the mask you selected. This is something you had to do, beforehand, using the Mask item, on the menu bar. Press the 'face'/mask button on the right side, again, and a red line shows through it, and the mask is not used for that layer (150K). The little '2 circle' button, just to the right of the mask button, links or 'locks' the mask and image together, so that both can be moved around together; otherwise, the mask stays put (which is generally what you want).

Layers can be grouped together so that, as with 'locking' masks, all can be moved together at once. And all layers in a group can be turned off and on at once, from the menu bar, Layers, View, Hide or Show. That's all grouping really does. By clicking the group buttons shown, using the right mouse button, it will count up to the number of layers, including background, and then start again, at "none". Press the group button with the left mouse, and it counts down.

Masks are grayscale images, which can be thought of like stencils, which allow some things to show through and others not. They are attached to a particular layer, and affect just that layer - not those underneath. Since they are grayscale, really anything that is a 256 shades of gray image could be use - a grayed out photograph, for example. More typically, the mask will have 'holes' for part of the layer to show through. Black won't let anything through. White lets things through. And gray shades in between tend to keep parts of that layer's image from showing, depending on how dark the gray is.

Masks can be loaded and saved, either to the alpha channel, or to disk. Each image has its own alpha channel. And more than one mask can be placed on the alpha channel for any particular image. A mask could be easily created by using the wand selection, for example, around some text (150K), then inverting (Selections, Invert from the menu bar, or press Shift-Ctrl-i). The selection can be saved to alpha, and the mask can be loaded right in from alpha to any particular layer - just that easily.

As just a grayscale image, the mask can be changed like any other image. A quick way, though, is to use the mask editing, right on the layer, by Masks, View Mask, and then Masks, Edit, from the menu bar. It might be useful to turn off all layers for that (Layers, View, None), to see just the mask.