Short for “Picture Element”
A single dot on a monitor or printed
The smallest rectangular area of an
image that can be manipulated on a
monitor or printer, or stored in memory.
A pixel has a unique associated colour
A pixel shows only one colour at a given
instant, but the possible colours may
vary according to the number of bits we
assign to each pixel.
If we assign a single bit (1 or 0) to a
pixel we can give that pixel only two
If we assign two bits to a pixel we can
give that pixel four colours
More colours / shades
Bits per pixel Number of different
Pictures & Formats
A picture is a set of pixels of different colours
placed in a particular pattern.
Pictures must be saved to disks as a
sequence of bits. There are several ways of
translating a picture to a series of bits. This
will give name to the format of the image file.
Some of them highly compress the image
(JPEG, GIF) occupying less space and some
of them not so much (BMP).
Examples: JPEG, GIF, BMP, TIFF, WPG,
Another graphic format
Graphic file formats can be:
Pixeled or Bitmapped
Object-oriented (or vector based)
Object oriented Bitmapped
Are stored as a series Are stored as pixels at
of lines or vectors. given coordinates.
Have smooth edges Have sharp edges
Can be enlarged Cannot be enlarged
without any loss of without loss of image
image quality. quality.
Not very good for Photographs and
photographs or complex complex images can
pictures (they occupy perfectly be stored (and
too much) compressed to a
Another comparison chart can be found in www.british.edu.uy/it_dept/itgs/graphics.jpg
Quality vs. Storage
Drawing vs. Painting
Drawing software manages objects
Painting software manages bitmaps
Monitor vs. Printer quality
Image digitalisation methods
Easy to replicate works of art
Easy the violation of intellectual
Computer Aided Design
It is the use of computers to design products.
Used mainly by engineers, designers and
It can help to visualize the product better
It can prevent design error, therefore
preventing serious catastrophes.
It can take very much less time to design a
It can lower the costs as the designer can
avoid buying experimental material.
Unskilled designers can build design-
poor products that may cause future
It may require lots of storage capacity.
The design may turn too complex and
have design problems
It is limited to the drawing skills of the
CAM systems are sometimes integrated
with a computer-aided design system
Very useful for circuit designers.