GIMP/Rectangle Selection

= The Basics =

Shortcut: R

The rectangle selection tool is a simple but useful tool. It allows you to create rectangular selections.


 * Modes - determines the way of creating the selection, whether it'll be combined with existing one and such
 * Antialiasing - causes the boundary of the selection to be drawn smoother
 * Feather edge - causes the boundary of the selection to be blurred
 * Rounded corners - rounds the corners of the selection
 * Expand from centre - expands selection, using starting point as the centre, instead for the corner
 * Fixed - allows you to modify the actual shape of rectangle
 * Position - placement of the selection
 * Size - size of the selection
 * Highlight - highlights the actual selection, by darkening everything that surrounds it
 * Guides - select the types of guides shown within of selection
 * Auto Shrink - shrinks the selection to the nearest rectangular shape available on the image layer
 * Shrink merged - if this option is enabled, then Auto Shrink will use the pixel information from the visible display of the image, rather than from the active layer

Modes, Antialiasing and Feather Edges

 * See Selection Tools#Modes for information about Modes
 * See Selection Tools#Antialiasing for information Antialiasing
 * See Selection Tools#Feather Edges for information about Feather Edges option

Rounded corners
A slider appears after enabling this option. Use it, to change the radius that is used to round the corners

Expand from centre
After enabling this option, the starting point is used as the centre of the selection instead of using it as a corner. This also causes that the selection is extended from all sides. This option can be enabled with Shift.

Fixed
This option allows you to modify the shape of rectangle in four ways:


 * Aspect ratio - allows you to design the selection, while keeping the aspect ratio fixed. By default it is 1:1, which makes a square. There are two little icons next to it (landscape and picture)
 * Width - you can fix the width of the selection
 * Height - you can fix the height of the selection
 * Size - you can fix both, width and height of the selection

Position
The actual placement of the current selection. This will show the placement of upper left corner, or centre, if Expand from centre option is enabled. You can use it to modify

Size
The actual size of the current selection. You can use it to modify the size, as well as resizing it directly on the image.

Highlight
Emphasizes the selected area by a surrounding mask, making the visual selection much easier.

Guides
In here you can set what guides will be shown within the selection, respecting Photo composition rules.


 * No guides - no guides are shown
 * Centre lines - only the centre lines are visible
 * Rule of thirds - guides are shown along the rule of thirds
 * Golden sections - guides show up to mark the golden sections

Auto Shrink
After pressing this button, already having a selection, it will shrink to the nearest rectangular shape within the selection. The algorithm for finding the best rectangle, can once do a great work, and sometimes find some strange rectangles.

Shrink merged
If this option is enabled Auto shrink will look on the actually visible image, rather than the active layer.