The image on the left is aliased, notice the jagged stair-step edges. The image on the right has anti-aliasing applied to the text.
Did you ever play with Lego building blocks as a child? Perhaps you noticed how hard it was to build an arch or a curve. The best you could achieve still had noticeable stair stepping. Guess what, pixels are just like those building blocks. Curved or diagonal lines will not look good at low resolutions, and you must soften the edge.
By choosing to use an Anti-aliasing method, Photoshop will generate smoother results—especially when using selection tools (such as the Quick Selection tool) or vector-based type. Anti-aliasing works by softening the color transition between edge pixels.
Since only the edge pixels are changed, you lose no detail in the image itself. Anti-aliasing is a useful option for creating text, making selections for filters, or copying and pasting. It will be a recurrent topic throughout this book. You can adjust the anti-aliasing for many tools directly in the Options bar. You should apply this option before a selection is made.
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