PHOTOSHOP TUTORIAL: use the Align + Transform Tools
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How to use alignment and transformation options:
1) Transform:
press "command + t" to open free transform
Holding down "shift" causes things to scale proportionally
Holding down "option" ("alt" on windows) causes objects to scale from the center
Holding down "command" ("windows key" on windows) allows you to move corners individual
You can also combine these in combination. For example holding down "command + shift + option" will scale opposite corners in a straight line towards the center creating a perspective effect.
2) Align:
select the area you'd want the object to be aligned relative to. now get the move tool (v) and youll see that there are a series of alignment options you can click at the top of the photoshop window. These allow you to quickly and accurately line up objects perfectly