# Channels Dialog

The Channels dialog

The Channels dialog is the main interface to edit, modify and manage your channels. Channels have a double usage. This is why the dialog is divided into two parts: the first part for color channels and the second part for selection masks.

Color channels apply to the image and not to a specific layer. Basically, three primary colors are necessary to render all the wide range of natural colors. As other digital software, GIMP uses Red, Green, and Blue as primary colors. The first and primary channels display the Red, Green, and Blue values of each pixel in your image.

Next to the channel name is a thumbnail displaying a grayscale representation of each channel, where white is 100% and black is 0% of the primary color. Alternatively, if your image is not a colored but a Grayscale image, there is only one primary channel called Gray. For an Indexed image with a fixed number of known colors there is also only one primary channel called Indexed.

Then there is an optional channel called Alpha. This channel displays transparency values of each pixel in your image (See Alpha Channel in Glossary). In front of this channel is a thumbnail displaying a grayscale representation of the transparency where white is opaque and visible, and black is transparent and invisible. If you create your image without transparency then the Alpha channel is not present, but you can add it from the Layers dialog menu. Also, if you have more than one layer in your image, GIMP automatically creates an Alpha channel.

GIMP doesn't support CMYK or YUV color models.

Representation of an image with channels

Red channel

Green channel

Blue channel

Alpha channel

All channels

The right image is decomposed in three color channels (red, green, and blue) and the Alpha channel for transparency. On the right image the transparency is displayed as a gray checkerboard. In the color channel white is always white because all the colors are present and black is black. The red hat is visible in the red channel but quite invisible in the other channels. This is the same for plain green and blue which are visible only in their own channels and invisible in others.

## Activating the Dialog

This dialog is a dockable dialog; see the section for help on manipulating it.

You can access it:

- from the main menu: Windows Dockable Dialogs Channels ;

- from the Tab menu in any dockable dialog by clicking on and selecting Add Tab Channels .

In the Windows menu, there is a list of detached windows which exists only if at least one dialog remains open. In this case, you can raise the Channels dialog from the main menu: Windows Channels .

## Using the Channels dialog

### Overview

The channels at the top are the color channels and the optional Alpha channel. They are always organized in the same order and they cannot be removed. In the middle are two lock buttons, that show the lock status for the currently selected channel in the bottom area. The bottom area shows a list of selection masks. Every channel appears in the list with its attributes, including a thumbnail and its name. A right-click in a channel list entry opens the channel context menu.

### Channel lock attributes

Above the list of selection mask channels are two check boxes that show the lock attributes state of the currently selected mask channel.

Lock pixels

  The paintbrush icon shows whether lock pixels is enabled (highlighted) for the current channel. When this is enabled, the channel is locked for any action that changes the pixels, meaning there will be no changes done to this channel.

Lock position and size

  The cross-with-arrows icon shows whether lock position and size is enabled (highlighted) for the current channel. When this is enabled, the channel is locked for any action that changes the position or size.

### Channel attributes

Every channel is shown in the list with its own attributes, which are very similar to the layer attributes:

Channel visibility

  By default every channel and thus every color value is visible. This is indicated by an open eye icon. Clicking on the eye-symbol (or the space if the channel is not visible) will toggle the visibility of the channel.

Chain channels

  The channels representing selection masks (in the lower part of the channel list) may be grouped using the button with the chain symbol. All channels that have the chain enabled will be affected in the same way by operations applied to any one of them.

  Primary color channels (the default channels in the upper part of the channel list) may be grouped too. By default, all color channels (and the alpha channel) are selected, their list entries are highlighted. Operations will be performed on all channels. By clicking on a channel list entry you can deactivate this channel. Operations like colorizing a layer will then be applied to the selected (grouped) channels only. Clicking on the deactivated list entry will activate the channel again.

Thumbnail

  A small preview icon represents the effect of the channel. This preview can be enlarged by holding down the left mouse button on it.

Channel name

  The name of the channel, which must be unique within the image. Double-clicking on the name of a selection mask channel will allow you to edit it. The names of the primary channels (Red, Green, Blue, Alpha) can not be changed. Double-clicking on the preview icon will open a dialog where you can set all channel attributes.

Activated channels appear highlighted 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 consequences. For instance if you disable the blue channel, all pixels from now on added to the image will not have a blue component, and so a white pixel will have the yellow complementary color.

### Managing channels

Below the channel list is a set of buttons allowing you to perform some basic operations on channel list.

New Channel

  This creates a new channel. A dialog will open where you can set the Channel name, the Color tag, the channel attributes and lock attributes, and finally the Opacity and color used for the mask in the image window. A click on the color button displays the GIMP color selector where you can change the mask color. If you press the Shift key while clicking the New Channel button, the New Channel Dialog will not be opened. Instead the new channel will be created with the same settings as used previously. This new channel is a channel mask (a selection mask) applied over the image. See Selection Mask

Raise Channels

  Only available for selection masks: this moves the selected channels up in the list. Press Shift key to move the channel to the top of the list.

Lower Channels

  This moves selected channels down in the list. Press the Shift key to move the channel to the bottom of the list.

Duplicate Channels

  This creates a copy of the active channels. The name of the new channel is suffixed with a number.

  You can also duplicate color channels or the Alpha channel. It's an easy way to keep a copy of them and to use them later as a selection in an image.

Replace the Selection with Selected Channels

  This transforms the selected channel to become a selection. By default the selection derived from channels replaces the active selection. You can change this by using control keys.

  - Shift: the selection derived from a channel is added to the active selection. The final selection is merged from both.

  - Ctrl: the final selection is the subtraction of the selection derived from a channel from the active selection.

  - Shift Ctrl : the final selection is the intersection of the selection derived from a channel with the active one. Only the selected parts common to both are kept.

Delete Channels

  Only available for selection masks: this deletes the selected channels.

Channel Edit Channel Attributes
Channel Create a New Channel Mask
Channel Move Channel Mask
Channel Duplicate Channel Mask
Channel Delete Channel Mask
Channel Channel to Selection
Dialogs Channels
Channel Dialog