About
bitmap images and vector graphics
Before working with vector shapes and vector paths, it's important
to understand the basic differences between the two main categories
of computer graphics: bitmap images and vector graphics. You can use
Photoshop to work with either type of graphic; in fact, you can combine
both bitmap and vector data in an individual Photoshop image file.
Bitmap images, technically called raster images, are based on a grid
of colors known as pixels. Each pixel is assigned a specific location
and color value. In working with bitmap images, you edit groups of
pixels rather than objects or shapes. Because bitmap graphics can
represent subtle gradations of shade and color, they are appropriate
for continuous-tone images such as photographs or artwork created
in painting programs. A disadvantage of bitmap
graphics is that they contain a fixed number of pixels. As a result,
they can lose detail and appear jagged when scaled up onscreen or
printed at a lower resolution than they were created for.
Vector graphics are
made up of lines and curves defined by mathematical objects called
vectors. These graphics retain their
crispness whether they are moved, resized, or have their color changed.
Vector graphics are appropriate for illustrations, type, and graphics
such as logos that may be scaled to different sizes. The
major disadvantage of using a vector image is the amount of effort
required to produce a highly detailed image.
