Page 169 - Enhancing CAD Drawings with Photoshop

4386.book Page 153 Monday, November 15, 2004 3:27 PM

TRANSFERRING MULTILAYER DRAWINGS TO PHOTOSHOP 153

Table 5.1: Common Scale Factors (continued)
Scale Ratio
1.5˝ 1´-0˝ : 8

1˝ 1´-0˝ : 12
3/4˝ 1´-0˝ : 16
1/2˝ 1´-0˝ : 24

3/16˝ 1´-0˝ : 64
1/8˝ 1´-0˝ : 96

3/32˝ 1´-0˝ : 128
1/16˝ 1´-0˝ : 192

1˝ 10´ : 120
1˝ 20´ : 240

1˝ 50´ : 600
1˝ 100´ : 1200

Transferring Multilayer Drawings to Photoshop
You have already seen how to transfer drawings from AutoCAD to Photoshop and maintain the
graphic scale in the image. Drawings transferred in this way appear on a single layer in Photoshop.
However, typical CAD drawings contain many layers, and more creative possibilities open up if you
can access these as individual image layers in Photoshop.
It is possible to transfer the layers from an AutoCAD drawing to a Photoshop image by printing
each layer one at a time and then integrating the image files in Photoshop. Fortunately for you, I have
written a program (included on the companion CD) that automates part of this process, saving you
many hours of tedium.
The program runs in AutoCAD and automates plotting by making each layer an image file. It is
called lay2img (layer to image) and is written in Autodesk’s subset of the ancient list processing lan-
guage (developed in the 1950s) called AutoLISP. Programming in AutoLISP is beyond the scope of
this book, although you will learn how to edit a few simple parameters in the program to suit your
needs.
After you load and use lay2img to print each layer as an image file, I’ll show you a technique in
ImageReady (Photoshop’s sister product) to automate the integration of the image files into layers
within a single document. Finally, we’ll use the Magic Eraser tool to composite the layers transpar-
ently together in a working Photoshop file.