The Layers dialog is the main interface to edit, modify and manage your
layers. You can think of layers as a stack of slides or clothes on your
body. Using layers, you can construct an image of several conceptual
parts, each of which can be manipulated without affecting any other part
of the image. Layers are stacked on top of each other. The bottom layer is
the background of the image, and the components in the foreground of the
image come above it.
Figure 9.2.
An image with layers
Layers of the image
Resulting image:
2.1.1.
Activate Dialog
The Layer dialog can be called in many ways :
from the toolbox-menu:
File->Dialog->Layers
from the image-menu:
Dialog->Layers
from an other dialog-menu:
Add Tab->Layers
from the (default) shortcut:
Ctrl-L
2.1.2.
Using the Layerdialog
Overview
Every layer appears in the dialog in the form of a thumbnail. When
an image has multiple layers as components, they appear as a list.
The upper layer in the list is the first one visible, and the
lowest layer the last visible, the background. Above the list one
can find characteristics related individually to each layer. Under
the list one can find management buttons for the layer list. A
right-click in a layer thumbnail opens the Layer
menu.
Layer attributes
Every layer is shown in the list along with its attributes. The
main attribute is the name of the layer. You can edit this by a
double-click on the name or the thumbnail of the layer. In front
of the thumbnail is an icon showing an eye
.
By clicking on the eye, you toggle whether the layer is visible
or not. (Shift-clicking on the eye causes all
other
to be temporarily hidden.) Another icon, showing a chain
,
allows you to group layers for operations on more than one layer
at a time (for example with the Move tool).
Tip
In the case of an animation layer (GIF or MNG), the name of the
layer can be used to specify certain parameters : Layer_name
(delay in ms) (combination mode), for example Frame-1 (100 ms)
(replace). The delay
sets the time during which the layer is visible in the
animation. The combination mode sets whether you combine the
layer with the previous layer or replace it: the two modes are
(combine) or (replace).
Layers characteristics
Above the layer list, it is possible to specify some properties
for the active layer. The active layer is the one highlighted in
blue. The properties are : "Layer mode", "Keep transparency", and
"Opacity".
Layer modes
Figure 9.3.
Layer modes
The layer mode determines how the layer interacts with the
other layers. From the combo box you can access all the modes
provided by GIMP. The layer modes are fully detailed in the
Glossary.
Keep transparency
Figure 9.4.
Keep transparency
If you check this option the transparent areas of the layer
will be kept, even if you have checked the
Fill transparent areas
option for the Bucket fill tool.
Opacity
Figure 9.5.
Opacity
By moving the slider you give more or less opacity to the
layer. With a 0 opacity value, the layer is transparent and
completely invisible. Don't confuse this with a Layer Mask,
which sets the transparency pixel by pixel.
Layer management
Under the layer list a set of buttons allows you to perform some
basic operations on the layer list.
Edit layer attributs
Here you can change the name of the active layer in the
list.
New layer
Here you can create a new layer. A dialog is opened where
you can enter the Layer name,
perhaps change the default Height
and Width, and choose the
Layer fill type
that will be the new layer's background.
Raise layer
Here you can move the layer up a level in the list. Press
the Shift
key to move the layer to the top of the list.
Lower layer
Here you can move the layer down a level in the list. Press
the Shift
key to move the layer to the bottom of the list.
Tip
To move a layer at the bottom of the list, it may first be
necessary to add a transparency channel (also called Alpha
channel) to the Background layer. To do this, right click
on the Background layer and select
Add Alpha channel from the menu.
Duplicate layer
Here you can create a copy of the active layer. Name of new
layer is suffixed with a number.
Anchor layer
When the active layer is a temporary layer (also called
floating selection) shown by this icon
,
this button anchors it to the previous active layer.
Delete layer
Here you can delete the active layer.
More layer functions
Other functions about layer size are
available in the Layer
Drop down menu you get by right clicking on the
Layer Dialog. You can find them also in the Layer sub-menu
of the image menu.
You will find merging layers functions
in the Image
submenu of the Image menu.
Clicking-and-dragging layers
Click and hold on layer thumbnail: it enlarges and you can
move it by dragging the mouse.
So you can put this layer down
somewhere else in the layer list.
You can also
put the layer down into Toolbox
: a new image is created that contains this layer only.
Finally, you can
put the layer down into another image
: this layer will be added to the layer list, above existing
layers.
2.1.3.
Layer masks
Revision History
Revision $Revision: 1.29 $
2006-03-09
lexa
Figure 9.6.
Dialog add mask
Overview
A transparency mask can be added to each layer, it's called Layer
mask. A layer mask has the same size and same pixel number as the
layer to which it is attached. Every pixel of the mask can then be
coupled with a pixel at the same location in the layer. The mask is
a set of pixels in gray-tone on a value scale from 0 to 255. The
pixels with a value 0 are black and give a full transparency to the
coupled pixel in the layer. The pixels with a value 255 are white
and give a full opacity to the coupled pixel in the layer.
To create a layer mask start with a right click on the layer to call
the context menu and select Add layer mask
in the menu. If the menu item is grayed first select
Add Alpha channel in the same menu. A dialog
appears where you can initialize the content of the mask:
White (full opacity): the mask has no
effect, all layer pixels are full visible.
Black (full transparency): the mask gives
a full transparency to the layer which becomes invisible.
Layer's alpha channel: the mask is
initialized according to the content of layer Alpha
channel. If the layer still contains transparency it's
copied in the mask.
Transfer layer's alpha channel:
Does the same thing as the previous option, except that it
also resets the layer's alpha channel to full opacity.
Selection : the mask is initialized
according to pixel values found in the selection.
Grayscale copy of layer: the mask
is initialized according to pixel values of the layer.
When the mask is created it appears as a thumbnail right to the
layer thumbnail. By clicking alternatively on the layer and mask
thumbnail you can enable one or other. The active item is
highlighted by a white border (which is not well visible around a
white mask). To view mask content instead of its effect in image
window, press
Ctrl-Alt
and then on mask thumbnail. Its borber turns to red. To return to
normal view redo last operation.
Caution
The layer mask acts like a transparency mask on a particular
layer. Since you have many layers it becomes different from the
image Alpha channel which represents transparency applied to the
whole image.
Published under the terms of the GNU General Public License
![[Tip]](../images/tip.png)
![[Caution]](../images/caution.png)
