Page 23 - Enhancing CAD Drawings with Photoshop

4386.book Page 6 Monday, November 15, 2004 3:27 PM

6 CHAPTER 1 THE BASICS

Figure 1.6
Smooth horizontal and vertical lines
The relationship of pixels
to grid

Jagged oblique line Perfect stairstep 45-degree lines

NOTE The relationship that pixels have with their implied grid determines how jagged they appear.

The 45-degree line also has a clean look because it is made of a perfect stairstep of pixels. Only
the oblique line seems jagged because it must be represented on this grid of pixels.
10. Hold down the spacebar and drag the mouse to the left in the document window to pan over
to the anti-aliased area of the image (see Figure 1.7).
The horizontal and vertical lines are perfectly represented because they align with the grid
of pixels. The 45-degree and oblique lines get an anti-aliasing treatment that blends the adja-
cent pixel colors to make the edge seem softer. Notice how the 45-degree anti-aliasing is sym-
metrical and that the oblique blending is a bit more complex.
11. Double click the Zoom tool in the toolbox to return to 100% magnification. Save this file as
Linework.psd. This file is also provided on the CD for your convenience.

Let’s compare a few items in Figures 1.6 and 1.7. First, the aliased oblique line in Figure 1.6 is unac-
ceptable because it is clearly jagged. Oblique lines therefore benefit from anti-aliasing. The horizontal
and vertical lines appear the same whether they are anti-aliased or not because they align with the grid
of pixels in the image. Finally, the lines that are at a 45-degree angle actually look better in Figure 1.6
because they appear thinner than the anti-aliased lines in Figure 1.7.