Technical data

34 Manipulating Images
If the selection you've made isn't quite the right shape, or doesn't quite
include all the necessary pixels (or perhaps includes a few too many),
you can continue to use the selection tools to add to, or subtract from,
the selected region. To add to the existing selection, drag with the
selection tool while holding down the Shift key. To subtract, drag while
holding down the Alt key. Pressing the Ctrl key changes the tool
temporarily to the Move tool (see below), so you can move the
selection’s content.
The Modify item on the Select menu provides a submenu with several
functions that can save you the trouble of hand-drawing to change the
selection boundaries. Choose Contract... to shrink the borders of the
selection, or Expand... to extend its borders.
Grow and Similar both expand the selection by seeking out pixels
close (in color terms) to those in the current selection. Grow only adds
pixels adjacent to the current selection, while Similar extends the
selection to any similar pixels in the active layer. Both of these use the
current tolerance value entered for the Color Selection tool (see above).
To remove the current selection, choose Deselect from the Select
menu, or use the keyboard shortcut Ctrl+D.
The Invert command on the Select menu (shortcut Ctrl+Shift+I) selects
the portion of the active layer outside the current selection. Unselected
pixels become selected, and vice versa.
Once you have selected precisely the pixels you want to work on (as
covered so far in this chapter), the question arises, what can you do with
the selection—or technically speaking, with the pixels you've outlined?
This rest of the chapter will survey the many possible manipulations
you can carry out.
Using the Move tool
The Move tool (unlike the Move Marquee cursor associated with
the selection tools) is for pushing actual pixels around. With it, you can
drag the content of a selection from one place to another, rather than
just moving the selection outline. To use it, simply click on the
selection and drag to the new location. The selected part of the image
moves also.
If nothing is selected, dragging with the Move tool moves the entire
active layer. Moving image content on the Background layers exposes a
“hole” that appears in the current background color; on standard layers,
exposed region is transparent.