Chapter 7: Getting Images Into Photoshop And Imageready; Bitmap Images And Vector Graphics - Adobe PHOTOSHOP CS2 User Manual

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Chapter 7: Getting images into Photoshop
and ImageReady

Bitmap images and vector graphics

Bitmap images and vector graphics
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. It's helpful to
understand the difference between the two categories as you create, edit, and import artwork.
See also
"Bitmap images" on page 177
"Vector graphics" on page 177
Bitmap images
Bitmap images—technically called raster images—are made up of a grid of dots known as pixels. 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 can lose detail when scaled on-screen because they are resolution-dependent, they contain a fixed
number of pixels, and each pixel is assigned a specific location and color value. Bitmapped images can look jagged if
they're printed at too low a resolution because the size of each pixel is increased.
3:1
24:1
Example of a bitmap image at different levels of magnification
Vector graphics
Vector graphics are made up of mathematically defined lines and curves called vectors. You can move, resize, or
change the color of a line 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 (logos, for example).