Getting Images Into; Photoshop And Imageready; About Bitmap Images And Vector Graphics - Adobe PHOTOSHOP 6.0 Manual

Chapter 2: Getting Images into

Photoshop and ImageReady

ou can get digital images from a variety of
Y
sources—you can create new images,
import them from another graphics appli-
cation, or capture them using a digital camera.
Often you will begin by scanning a photograph,
a slide, or an image. To create effective artwork,
you must understand some basic concepts about
how to work with digital images, how to produce
high-quality scans, how to work with a variety of
file formats, and how to adjust the resolution and
size of images.
About bitmap images and vector
graphics
Computer graphics falls into two main
categories—bitmap and vector. You can work with
both types of graphics in Photoshop and
ImageReady; moreover, a Photoshop file can
contain both bitmap and vector data. Under-
standing the difference between the two categories
helps as you create, edit, and import artwork.
Bitmap images—technically
Bitmap images
called raster images—use a grid of colors known as
pixels to represent images. Each pixel is assigned a
specific location and color value. For example,
a bicycle tire in a bitmap image is made up of a
mosaic of pixels in that location. When working
with bitmap images, you edit pixels rather than
objects or shapes.
Bitmap images are the most common electronic
medium for continuous-tone images, such as
photographs or digital paintings, because they can
represent subtle gradations of shades and color.
Bitmap images are resolution-dependent—that is,
they contain a fixed number of pixels. As a result,
they can lose detail and appear jagged if they are
scaled on-screen or if they are printed at a lower
resolution than they were created for.
Bitmap images are good for reproducing subtle gradations
of color, as in photographs. They can have jagged edges
when printed at too large a size or displayed at too high a
magnification.
Vector graphics are made up of
Vector graphics
lines and curves defined by mathematical objects
called vectors. Vectors describe an image according
to its geometric characteristics. For example, a
bicycle tire in a vector graphic is made up of a
mathematical definition of a circle drawn with a
certain radius, set at a specific location, and filled
with a specific color. You can move, resize, or
change the color of the tire without losing the
quality of the graphic.
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