Image Processing Reference
An image object is bound to a layer. A selection isn't. You can create a
selection on one layer and apply it to any other layer. It works only on the
active layer. The active layer is the layer that is selected. Therefore, it is marked
in the Layers dialog by a different color. However, only when you carry out a
work step (i.e., filling, color corrections, or copying) does something happen
on the chosen layer. When copying, this isn't even an alteration of the image
content of the selected layer. Only through a subsequent insertion will
something visible happen.
This is of great importance when
working with selections and layers.
3.3.1 The Layers Dialog
You can access the Layers dialog either from within the Windows > Dockable
Dialogs menu item or from the Windows > Layers, Channels, Paths, Undo menu
item in the image window. By default, when you start GIMP, it displays the
Layers dialog in a window together with the dialogs for channels, paths, and
the undo history. You can click a tab to select one of these dialogs (upper area
in figure 3.8).
Here are the options in the Layers dialog:
• Auto : This button determines whether the Layers dialog should
automatically display the layers of the current image window if you have
several image windows open concurrently. Note that from your active
image, an entry may not appear in the Layers dialog nor in the Channels ,
Paths , or Undo History dialog. You can activate it by clicking the Auto
button and the entry should appear.
• Mode : This option determines how a layer interacts with other layers. The
default mode is Normal .
• Opacity : This option lets you adjust the opacity of the layer. Move the
slider to obtain a translucent layer fill. In the example image, the window
pane layer was set to semitransparent opacity.
• Lock : The check box (with the chessboard pattern next to it) serves the
purpose of protecting the transparencies. If Lock is activated, you cannot
alter the transparent section of a layer.
The Layers, Channels, Paths, Undo
window (Layers dialog)