Computer
graphics fall 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.
Understanding the difference between the two
categories helps as you create, edit, and
import artwork.
Bitmap images
Bitmap images--technically 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.
Bitmaps include terms as Jpeg, Gif, PNG,
Tiff and other 'flat' images.
Vector
graphics
Vector graphics are made up of 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.
Vector graphics are
resolution-independent--that is, they can be
scaled to any size and printed at any
resolution without losing detail or clarity.
As a result, vector graphics are the best
choice for representing bold graphics that
must retain crisp lines when scaled to
various sizes--for example, logos.
NOTE: We only use Photoshop for photos,
Every time we make a sign, we use our
drawing programs to create sharp texts,
logos and art.
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