Page 62 - Enhancing CAD Drawings with Photoshop

4386.book Page 45 Monday, November 15, 2004 3:27 PM

SIZING AND TRANSFORMING 45

You can create your own custom shapes and even save them in your own libraries for future use.
You can share shape libraries with other people because they are stored as files by Photoshop. Refer
to Chapter 5, “Presenting Plans,” in which you will create a graphical scale bar and save it in your
own custom shape library.

Sizing and Transforming
Images can be stretched and shrunk, rotated and resized, and otherwise transformed to fit your
needs. All these transformations are mathematical manipulations of the pixels in your image. As
such, extreme manipulations tend to alter the original data so much that image quality and believ-
ability can be lost. On the other hand, more conservative changes can help improve an image while
maintaining its “truth” as a representation of reality.

Setting Image Size, Resolution, and Document Size
Image size, resolution, and document size form a trinity of factors that are involved in a relationship.
Changes to any of these three factors affect the others. You manage this relationship from the Image
Size dialog box.
You will open a sample file to explore the Image Size command.
1. Open the file Lunch.psd from the CD.
2. Choose Image Image Size to open the Image Size dialog box.
3. To begin with, make sure the Resample Image checkbox is unchecked. While this setting is off,
the relationship mentioned earlier is made simpler.
4. Note that the Document Size is currently more than 11 by 8 inches while the resolution is
72 pixels per inch. Change the resolution to 200. The width and height automatically adjust to
4 by 3 inches.

NOTE Traditionally screen resolution is either 72 or 96 pixels per inch (ppi). Most web design work
is done at 72 ppi.

5. Change Width from 4 inches to 8. As you do this, the other two parameters (Height and Res-
olution), automatically change, so the image now measures 8 by 6 inches with a resolution of
100 pixels per inch.

NOTE Resolution and document size are inversely proportional; you trade one for the other.
6. Place a check in the Resample Image check box. This enables the 2-pixel dimension parameters
(see Figure 1.45).
7. Change Width in the Pixel Dimensions group to 1000. As you do this, notice that the document
size has increased (10 by 7.5 inches) while the resolution remains constant. Also note that the
file size has increased because more pixels must now be stored.
8. Click the Cancel button in the Image Size dialog box to discard the changes you made while
experimenting.