Gimp - 2.4 Guía Del Usuario
GNU Image Manipulation Program
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• from the toolbox-menu: File → Dialogs → Channels
• from the image-menu: Dialogs → Channels
• from another dialog-menu: Add Tab → Channels
13.2.2.2
Using the Channel dialog
13.2.2.2.1
Overview
The top channels are the color channels and the optional Alpha channel. They are always organized in the same order and they
cannot be erased. Selection masks are described below and displayed as a list in the dialog. Every channel appears in the list in
form of a thumbnail. A right-click in a channel thumbnail opens the
cannot be erased. Selection masks are described below and displayed as a list in the dialog. Every channel appears in the list in
form of a thumbnail. A right-click in a channel thumbnail opens the
13.2.2.2.2
Channel attributes
Every channel is shown in the list with its own attributes. The main attribute is the name of the channel itself. You can edit
selection masks by double-clicking on their name. A double_click on the thumbnail opens a full dialog where you can also set
selection masks by double-clicking on their name. A double_click on the thumbnail opens a full dialog where you can also set
the visual aspect of the channel in the image window. In front of the thumbnail there is an eye icon:
by clicking on it
you define whether the channel is visible or not. As a result of this visibility, the view of the image changes in the image window
and a white image becomes yellow if you remove the view of the blue because yellow is the complementary color for blue. If
you remove the view of the Alpha channel, everything becomes transparent and nothing else than a grey checkerboard is visible.
and a white image becomes yellow if you remove the view of the blue because yellow is the complementary color for blue. If
you remove the view of the Alpha channel, everything becomes transparent and nothing else than a grey checkerboard is visible.
The aspect of this virtual background can be changed in the
. The chain icon
enables grouping of channels for
operations on multiple channels.
Caution
Activated channels appear highlighted (generally) in blue in the dialog. If you click on a channel in the list you toggle
activation of the corresponding channel. Disabling a color channel red, blue, or green has severe consequencies. For
instance if you disable the blue channel, all pixels from now on added to the image will not have blue component, and
so a white pixel will have the yellow complementary color.
Activated channels appear highlighted (generally) in blue in the dialog. If you click on a channel in the list you toggle
activation of the corresponding channel. Disabling a color channel red, blue, or green has severe consequencies. For
instance if you disable the blue channel, all pixels from now on added to the image will not have blue component, and
so a white pixel will have the yellow complementary color.
13.2.2.2.3
Managing channels
Under the channel list is a set of buttons allowing you to perform some basic operations on channel list.
Edit channel attributes, only available for selection masks. Here you can change the Channel name. The other two
parameters affect channel is visibility in the image window; they control Opacity and color used for the mask in the image
window. A click on the color button displays the Gimp color selector and then you can change the mask color.
window. A click on the color button displays the Gimp color selector and then you can change the mask color.
New channel You can create here a new channel. The displayed dialog lets you set Opacity and mask color used in the
image to represent the selection. (If you use the New Channel button in Channel Menu, you can create this new channel
with the options previously used by pressing the Shift key when clicking). This new channel is a channel mask (a selection
mask) applied over the image. See
with the options previously used by pressing the Shift key when clicking). This new channel is a channel mask (a selection
mask) applied over the image. See
Raise channel, only available for selection masks : you can here put the channel up a level in the list. Press Shift key
to move channel to top of the list.
Lower channel You can here put the channel down a level in the list. Press the Shift key to move the channel to
bottom of the list.
Duplicate channel You can create here a copy of the active channel. Name of new channel is suffixed with a number.