3
3
<html xmlns="http://www.w3.org/1999/xhtml">
5
5
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
6
<title>3.2. Selection masks</title>
6
<title>3.2. Using the Channeldialog</title>
7
7
<link rel="stylesheet" href="gimp-help-plain.css" type="text/css" />
8
8
<link rel="stylesheet" href="gimp-help-screen.css" type="text/css" />
9
<meta name="generator" content="DocBook XSL Stylesheets V1.64.1" />
10
<link rel="home" href="index.html" title="GIMP User Manual" />
9
<meta name="generator" content="DocBook XSL Stylesheets V1.66.1" />
10
<link rel="start" href="index.html" title=" " />
11
11
<link rel="up" href="ch04s03.html" title="3. Channels dialog" />
12
<link rel="previous" href="ch04s03.html" title="3. Channels dialog" />
13
<link rel="next" href="ch04s03s03.html" title="3.3. Quick Mask" />
12
<link rel="prev" href="ch04s03.html" title="3. Channels dialog" />
13
<link rel="next" href="ch04s03s03.html" title="3.3. Channels Menu" />
16
<div class="navheader">
16
<div xmlns="" class="navheader">
17
17
<table width="100%" summary="Navigation header">
19
<th colspan="3" align="center">3.2. Selection masks</th>
19
<th colspan="3" align="center" id="chaptername">3.2. Using the Channeldialog</th>
22
22
<td width="20%" align="left"><a accesskey="p" href="ch04s03.html">Prev</a> </td>
23
<th width="60%" align="center">3. Channels dialog</th>
23
<th width="60%" align="center" id="sectionname">3.2. Using the Channeldialog</th>
24
24
<td width="20%" align="right"> <a accesskey="n" href="ch04s03s03.html">Next</a></td>
30
30
<div class="titlepage">
33
<h3 class="title"><a id="dialogs-selection-masks"></a>3.2. Selection masks</h3>
33
<h3 class="title"><a id="id3335034"></a>3.2. Using the Channeldialog</h3>
38
<div class="mediaobject">
39
<img src="../images/dialogs/dialogs-channel-masks.png" />
42
Channels can be used to save and restore your selections. Clicking
43
on the <span class="guilabel">Quick mask</span> button on the <a href="">Image window</a> automatically
44
creates a new channel called <span class="guilabel">Qmask</span> and saves the
45
displayed active selection to a thumbail in front of the
46
channel.There are many selection tools in the Gimp like rectangular
47
selection tool or fuzzy selection for continuous selections.
48
Selection Masks are a graphical way to build selections into a gray
49
level channel where white pixels are selected and black pixels are
50
not selected. Therefore gray pixels are partially selected. You can
51
think of them as feathering the selection, a smooth transition
52
between selected and not selected. This is important to avoid the
53
ugly pixelization effect when you fill the selection or when you
54
erase its content after isolating a subject from background.
56
37
<div class="variablelist">
58
<b>Creating Selection Masks</b>
40
<span class="term">Overview</span>
64
There are several ways to initialize a selection mask. From the
66
<span class="guimenuitem"><span class="accel">S</span>elect</span>/
67
<span class="guimenuitem">Save to <span class="accel">C</span>hannel</span> is
68
available if there is an active selection. From the image window
69
the bottom-left button creates a <a href="ch04s03s03.html" title="3.3. Quick Mask">Quick
70
Mask</a>; the content will be initialized with the active
71
selection. From the channel dialog, when you click on the
72
<span class="guilabel">New channel</span> button or from the context menu.
44
The top channels are the color channels and the optional Alpha
45
channel. They are always organized in the same order and they
46
cannot be erased. Selection masks are described below and
47
displayed as a list in the dialog. Every channel appears in
48
the list in form of a thumbnail. A right-click in a channel
49
thumbnail opens the <a href="ch04s03s03.html" title="3.3. Channels Menu">channel
77
<div class="variablelist">
79
<b>Using Selectionmasks</b>
54
<span class="term">Channel attributes</span>
85
Once the channel is initialized, selected (highlighted in blue),
86
visible (eye-icon in the dialog), and displayed as you want
87
(color and opacity attributes), you can start to work with all
88
the paint tools. The colors used are important. If you paint
89
with some color other than white, grey, or black, the color Value
90
(luminosity) will be used to define a gray (medium, light, or
91
dark). When your mask is painted, you can transform it to a
92
selection by clicking on the <span class="guilabel">Channel to
93
selection</span> button or from the context menu.
95
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
96
<table border="0" summary="Tip">
98
<td rowspan="2" align="center" valign="top" width="25">
99
<img alt="[Tip]" src="../images/tip.png" />
101
<th align="left">Tip</th>
104
<td colspan="2" align="left" valign="top">
105
You can work in selection masks not only with the paint tool but
106
also with other tools. For instance, you can use the selection
107
tools to fill areas uniformly with gradients or patterns. By
108
adding many selection masks in your list you can easily compose
109
very complex selections. One can say that a selection mask is to
110
a selection as a layer is to an image.
58
Every channel is shown in the list with its own attributes. The
59
main attribute is the name of the channel itself. You can edit
60
selection masks by double-clicking on their name. A
61
double_click on the thumbnail opens a full dialog where you can
62
also set the visual aspect of the channel in the image window.
63
In front of the thumbnail there is an eye icon:
64
<span class="guiicon">
65
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-eye.png" /></span>
67
by clicking on it you define whether the channel is visible or
68
not. As a result of this visibility, the view of the image
69
changes in the image window and a white image becomes yellow if
70
you remove the view of the blue because yellow is the
71
complementary color for blue. If you remove the view of the
72
Alpha channel, everything becomes transparent and nothing else
73
than a grey checkerboard is visible. The aspect of this virtual
74
background can be changed in the
75
<a href="ch04s18.html" title="18. Preferences">Preferences</a>.
77
<span class="guiicon">
78
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-vchain.png" /></span>
80
enables grouping of channels for operations on multiple channels.
115
82
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
116
83
<table border="0" summary="Caution">
124
91
<td colspan="2" align="left" valign="top">
125
As long as a selection mask is activated you are working in the
126
mask and not in the image. To work in the image you have to
127
deactivate all selection masks. Don't forget also to stop
128
displaying masks in the image by removing the eye icon. Check
129
also that all RGB and Alpha channels are activated and displayed
93
Activated channels appear highlighted in blue in the dialog.
94
If you click on a channel in the list you toggle activation
95
of the corresponding channel. Disabling a color channel red,
96
blue, or green has severe consequencies. For instance if you
97
disable the blue channel, all pixels from now on added to the
98
image will not have blue component, and so a white pixel will
99
have the yellow complementary color.
107
<span class="term">Managing channels</span>
111
Under the channel list is a set of buttons allowing you to
112
perform some basic operations on channel list.
116
<div class="itemizedlist">
120
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-edit.png" /></span>
121
<a id="gimp-channel-edit"></a>
122
<span class="guilabel">Edit channel attributes</span>, only
123
available for selection masks. Here you can change the
124
<span class="guilabel">Channel name</span>. The other two
125
parameters affect channel is visibility in the image
126
window; they control <span class="guilabel">Opacity</span> and
127
color used for the mask in the image window. A click on
128
the color button displays the Gimp color selector and
129
then you can change the mask color.
134
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-new.png" /></span>
135
<a id="gimp-channel-new"></a>
136
<span class="guilabel">New channel</span>: you can create here a
137
new channel available to save a selection. Displayed
138
dialog lets you change <span class="guilabel">Opacity</span> and
139
mask color used in the image to represent the selection.
144
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-raise.png" /></span>
145
<a id="gimp-channel-raise"></a>
146
<span class="guilabel">Raise channel</span>, only available for
147
selection masks : you can here put the channel up a level
148
in the list. Press <span><b class="keycap">Shift</b></span> key to move
149
channel to top of the list.
154
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-lower.png" /></span>
155
<a id="gimp-channel-lower"></a>
156
<span class="guilabel">Lower channel</span>:
157
You can here put the channel down a level in the list.
158
Press the <span><b class="keycap">Shift</b></span> key to move the channel
159
to bottom of the list.
164
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-duplicate.png" /></span>
165
<a id="gimp-channel-duplicate"></a>
166
<span class="guilabel">Duplicate channel</span>: You can create
167
here a copy of the active channel. Name of new channel is
168
suffixed with a number.
170
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
171
<table border="0" summary="Tip">
173
<td rowspan="2" align="center" valign="top" width="25">
174
<img alt="[Tip]" src="../images/tip.png" />
176
<th align="left">Tip</th>
179
<td colspan="2" align="left" valign="top">
181
You can also duplicate a color channel or the Alpha
182
channel. It's an easy way to keep a copy of them and to
183
use them later as a selection in an image.
192
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-delete.png" /></span>
193
<a id="gimp-channel-selection-delete"></a>
194
<span class="guilabel">Delete channel</span>,only available for
195
selection masks: you can here delete the active channel.
200
<span class="inlinemediaobject"><img src="../images/dialogs/dialogs-icon-selection.png" /></span>
201
<a id="gimp-channel-selection-replace"></a>
202
<span class="guilabel">Channel to selection</span>: here you can
203
transform the channel to become a selection. By default
204
the selection derived from a channel replaces any
205
previous active selection. It's possible to change this
206
by clicking on control keys.
208
<div class="itemizedlist">
212
<a id="gimp-channel-selection-add"></a>
213
<span><b class="keycap">Shift</b></span>: the selection derived from a
214
channel is added to the previous active selection.
215
The final selection is merged from both.
220
<a id="gimp-channel-selection-subtract"></a>
221
<span><b class="keycap">Ctrl</b></span>: the final selection is the
222
substraction of selection derived from a channel from
223
the previously active one.
228
<a id="gimp-channel-selection-intersect"></a>
229
<span><b class="keycap">Shift Ctrl</b></span>: the final selection is
230
the intersection of selection derived from a channel
231
with the previously active one. Only common parts are
added
removed
html/en/ch04s03s02.html
