Selections

Topics
Adding to and Subtracting from
Modifying
'Dynamic Swapping' between Lasso Tools
'Undoing' and 'Escaping' from
Proportionality of
Transforming

Clive R. Haynes FRPS

Having made a 'selection' one frequently wishes to modify the outline. This can be done by either adding or subtracting from the shape.
The options of 'Adding', 'Subtracting' and 'Intersecting' appear as icons along the top left of the 'Options' bar and are represented by various overlapping squares. 'Hovering' with the cursor over an icon will will reveal its function.
The icons are useful but the most efficient method of usage is to use the Shift and Alt keys.

Adding
To add to a section, simply hold the shift key down [ a small + ('plus') sign appears next to the 'cross-hair cursor / tool symbol ] and proceed to use the chosen selection tool as normal.

Subtracting
To subtract from a section, simply hold the Alt key down [ a small - ('minus') sign appears next to the 'cross-hair cursor / tool symbol ] and proceed to use the chosen selection tool as normal.

Intersecting
This is a strange one but useful sometime. By holding down both Shift and Alt keys, an 'X' appears next to the 'cross-hair cursor / tool symbol. This in effect cuts away everything outside the area where the two selected areas overlap.

Using 'Quick Mask' to modify a selection

Another way of adding and subtracting is to use the Quick Mask facility. Go to the base of the Tool Bar and click on the small grey rectangle with the circular white centre. This will immediately show, in red, the area that is outside the selection.

Use a brush tool to add and subtract from the red area by selecting either black or white as the brush / foreground colour - this will add to the red area (with black / foreground paint chosen) or subtract from the red area (with white / foreground paint chosen). Swap between the two (using the 'X' key will make swapping between F/G and B/G quicker) and paint the selection to the shape required.

Click on the left-hand Quick Mask rectangle - the one with a dotted line circle, to view the selection as 'marching ants' once again. Swap back to Quick Mask mode to modify if necessary.

This is interesting and very useful. When using the freehand lasso, the polygon lasso or the magnetic lasso tool, it's possible to swap between them for greater selection flexibility during the same act of selection. See below .........

1: Freehand to Poly. When using the freehand lasso, hold down the 'Alt' key and lo and behold, the tool changes to the polygon lasso function as long as you hold it down. Release 'Alt' and you're back to freehand mode.

2: Poly to Freehand. Conversely, when using the polygon lasso hold down the 'Alt' key and lo and behold, the tool changes to the fee-hand lasso function as long as you hold it down. Release 'Alt' and you're back to polygon mode.

3: Magnetic to Poly. When using the magnetic lasso hold down the 'Alt' key and lo and behold, the tool changes to the polygon lasso function as long as you hold it down. Release 'Alt' and you're back to magnetic mode.

4: Three in One. Now this is cleaver stuff. There is a way to swap between all selection tools above i.e.. Freehand, Poly and Magnetic. Select the Magnetic Lasso. 'Select' using the lasso as normal, to change to 'Poly' mode simply (as described above) hold down the Alt Key and 'click' from point to point. To swap to 'Freehand' mode, once again, hold down the Alt Key and 'draw' as in 'freehand'. So to use the method 'on the wing' select Magnetic Lasso and keep your finger poised above the Alt Key to swap modes as you go! To delete sections of the selection - press 'delete'. To 'select' precise horizontal, vertical or 45 degree sections, hold down the Shift Key - if necessary, in conjunction with the Alt Key as required.

Undoing
The polygon lasso can be undone step-by-step (node-to-node) by using the 'Delete' key. Holding down the 'Delete' key will also undo the freehand sections of the line created by swapping to that tool whether originating in freehand or poly lasso mode. It unravels the freehand parts slowly like a ball of string!

Escaping from the 'Polygon Mesh'
Frequently people get into an awful mess (looks like a bad case of knitting!) when using the polygon lasso tool when they discover that they can't find the end or simply wish to quit. To escape, simply press the Esc (Escape) key.

Making Selections with a Proportional Square / Rectangular Shape
This applies to both the Rectangular and Circular selection marquee tools. To keep the proportions symmetrical (that is either square or circular) hold the Shift key down whilst making the selection. When the shape is as required, release the mouse button or (Wacom) pen before the Shift key.

Making Selections from the 'centre' with a Proportional Shape
To start drawing from the centre of a required area, whilst retaining the equal proportions of the Rectangular or Circular selection marquee tool, hold down both the Shift and Alt keys simultaneously whilst making the selection. When the shape is as required, release the mouse button or (Wacom) pen before the Shift & Alt keys.

Once the selection has been made go to:
Select > Transform Selection

Once 'Transform Selection' has been opened, little 'handles' appear around the selection.
This option works just like 'Free Transform'.

Proportional increase / decrease in size - hold down the Shift key, click / drag a 'handle'.

Zoom Proportional increase / decrease in size - hold down the Shift & Alt keys, click / drag a 'handle'.

Distortion of shape - hold down the Ctrl key, click / drag a 'handle'.

Trapezoidal Distortion of Shape - hold down the Ctrl & Alt keys, click / drag a 'handle'.

'Perspective' Distortion of Shape - hold down the Ctrl, Shift & Alt keys, click / drag a 'handle'.

NB: Release the mouse button or (Wacom) graphics pen before the Key / keys.

Use 'Enter' to confirm the transformation or 'Esc' to cancel the operation.