On both the Input Selection and Output Transformation stages, there are several shortcuts, key modifiers and contextual menus to help you move and reshape your slices.
Ctrl-Z and Ctrl-Y (Cmd-Z and Cmd-Y on a Mac) undo and redo your last steps.
Hold down Shift while dragging to constrain movement to either the x or y axis.
Hold down Alt while dragging to make a duplicate.
Hold down Ctrl while dragging to temporarily disable snapping.
Hold down Shift while scaling slices to constrain aspect ratio.
Hold down Alt while scaling to scale from the center, rather than the opposite end.
Hold down Shift while rotating to constrain rotation to 45 degree angles.
Ctrl-+ and Ctrl-- (Cmd-+ and Cmd-- on a Mac) zoom in and out.
Mouse scroll wheel zooms in and out.
Hold down spacebar while dragging to pan around the stage.
Use the keyboard arrow keys to nudge 1 pixel at a time .
Hold down Shift while nudging to nudge 10 pixels at a time.
Duplicate with Ctrl-D (Cmd-D on a Mac).
When first using Alt-Drag to make a transformed copy, Ctrl-D will then duplicate and repeat the transformation.
Backspace deletes the selected slice(s).
Double click anywhere on the path to add a point there.
Double click a point to delete.
Shift-click a point to add/remove it from the selection.
These differ per item, but generally will let you quickly access frequently used scalings and positions.
Center X centers the slice on the x-axis.
Center Y centers the slice on the y-axis.
Mirror X places the slice exactly on the opposite side of the center x-axis.
Mirror Y places the slice exactly on the opposite side of the center y-axis.
Left half, Right half, Bottom half, Top half scale the slice to exactly that half.
Whole Area scales the slice to the whole stage. This is handy reset option for when you've messed things up beyond repair.
Make Triangle creates a triangle shape that fills the entire stage.
Make Circle creates a circle shape that fills the entire stage.
Bring Forwards/Backwards moves the slice up or down in the slice stack. This is essentially the same as dragging the slice around in the slice list on the left side.
These are so important and useful, we've singled them out for you. They will let the slice take the position and shape that it has on the other stage. This way you can quickly match aspect ratios and positioning on the Input Selection stage to the Output Transformation stage or vice versa.
These will let you load a still image file in the background, to use a guide while lining up your slices.
It will load the file at its native resolution and position it in the top left of your screen.
You can adjust the opacity of the input map via the Opacity slider.
Loaded the wrong map to the wrong screen? Replace it via drag and dropping the right one, or remove it with the 'X' button.
This will show the outlines and a grid for the selected slice.
This will divide the output up into 8x8 pixel lines. When snapping is enabled, your slices will then snap to this grid. This is useful for making LED pixelmaps, since 99% of LED screens are made up of blocks of 8 pixels.
This will light up your slices in white when you mouse-over them. In combination with Show in Output, this is a great way to make sure your input map lines up with your actual stage. Or to quickly make sure which slice you need to adjust.
With this enabled, the Image Guides will show in the actual output. This is very useful to double check if everything is aligned correctly.
Also, when Slice Grid is enabled, it will show both the grid as well as a red crosshairs on the actual output, to help you get your bearings.