Getting Images Into Photoshop; About Bitmap Images And Vector Graphics - Adobe PHOTOSHOP 5.0 User Manual

Chapter 3: Getting Images into
Photoshop
I
n Adobe Photoshop, you can create new
images, import them from another graphics
application, or capture them from video. 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 fall into two main
categories—bitmap images and vector graphics.
Understanding the difference between the two
will help as you create and edit digital images.
Bitmap images
Photoshop and other paint and image-editing
programs generate bitmap images, also called
raster images. Bitmap images use a grid (the
bitmap or raster) of small squares 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.
A bitmap image is resolution-dependent—that is,
it contains a fixed number of pixels to represent its
image data. As a result, a bitmap image can lose
detail and appear jagged if viewed at a high magni-
fication on-screen or printed at too low a
resolution. Bitmap images are the best choice
for representing subtle gradations of shades and
color—for example, in photographs or painted
images.
Vector graphics
Drawing programs such as Adobe Illustrator
create vector graphics, made of lines and curves
defined by mathematical objects called vectors.
Vectors describe graphics according to their
geometric characteristics. For example, a bicycle
tire in a vector graphic is made up of a mathe-
matical 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.
A vector graphic is resolution-independent—that
is, it can be scaled to any size and printed on any
output device at any resolution without losing its
detail or clarity. As a result, vector graphics are the
best choice for type (especially small type) and
bold graphics that must retain crisp lines when
scaled to various sizes—for example, logos.
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