3.5. Quick Mask

A Quick Mask is a Selection Mask intended to be used temporarily to paint a selection. Temporarily means that, unlike a normal selection mask, it will not be saved in the list after its transformation to selection. The selection tools sometimes show their limits when they have to be used for doing complex drawing selection, as progressive. In this case, using the QuickMask is a good idea which can give very good results.

Activate Tool

  • The QuickMask can be activated in the following order, from the image-menu: Select/Toggle QuickMask.

  • The QuickMask can also be activated by clicking the left-bottom button showed in red on the screenshot.

  • It can also be activated by using Shift+Q shortcut.

Creating a Quick Mask

To initialize a Quick Mask, click the bottom-left button in the image window. If a selection was active in your image, then its content appears unchangedwhile the border is covered by a tranlucent red color. If no selection was active then all the image is covered by a tranlucent red color. At every moment you can hide the maskby clicking on the eye icon in front of the QMask. From the channel dialog you can double click on the name or the thumbnail to edit the QMask attributes. Then you can changethe Opacity and its filling color. Once a quick mask is initialized click on it to be sure it is selected and blue highlighted in the list, and start to paint on it with any Gimp paint tool. The mask is coded in gray tones, so you must use white or gray to decrease the area limited by the mask and black to increase it. The area painted in light or dark gray will be transition areas for the selection like feathering. When your mask is ready, click again on the bottom-left button in the image window and the quick maskwill be removed from the channel list and converted to aselection. Quick mask's purpose is to paint a selection and its transitions with the paint tools without worrying about managing selection masks. It's a good way to isolate asubject in a picture because once the selection is made you only have to remove its content (or inverse if the subject is in the selection).

Using Quick Mask's

Description

1

Screenshot of the image window with activated QuickMask. The QuickMask is filled with a gradient from black (left) to white (right).

2

The QuickMask is now disabled and a selection is initialised from the QuickMask, which was filled by a gradient before. You see the selection borders in the middle of the image.

3

A stroke is now added during the enabled selection. The key is, that the black color will have no opacity of the resulting stroke (right) and white color will have a full opacity of the stroke (left).

After the QuickMask Button is pressed, the command generates a temporary 8-bit (0-255) channel, on which the progressive selection work is stored. If a selection is already present the mask is initialized with the content of the selection. Once QuickMask has been activated, the image is covered by a red semi-transparent veil. This one representes the non-selected pixels. Any paint tool can be used to create the selection on the QuickMask. They should use only greyscale color, conforming the channel properties, white enabling to define the future selected place. The selection will be displayed as soon as the QuickMask will be toggled but its temporary channel will not be available anymore.

[Tip] Tip

To save in a channel the selection done with the Quickmask select in the image menu Select/Save to Channel

Usage

  1. Open an image or begin a new document.

  2. Activate the Quickmask using the left-bottom button in the image window. If a selection is present the mask is initialized with the content of the selection.

  3. Choose a drawing tool and use it with greyscale colors on the QuickMask.

  4. Deactivate the Quickmask using the left-bottom button in the image window.