Page 12 - DCAP504_Computer Graphics

Unit 1: Fundamentals of Computer Graphics

4. Menus: Menu helps the user to select a command from a list of options to execute a function.
5. Scroll Bars: Scroll bars help the user to scroll sideways, up and down on a page or application.
A GUI offers a simple and easy modification means and data entry. GUI even helps a computer illiterate
to use the system easily. With the help of GUIs, one can use a mouse to run programs, edit, copy, and
delete files by selecting appropriate options from the menus. GUI also partitions the display screen into
different sections or regions, wherein the outputs of different applications or programs are shown.
Thus, GUIs offer a better means of communication with computer as compared to unwieldy text based
interfaces.
Adoption of a standard GUI proves to be very helpful, since a standard GUI maintains the consistency
of use across all the platforms and applications. All the Microsoft Windows and Apple Macintosh
applications have similar look and feel. Therefore, the learning time for a new application does not take
much time. Today, it is possible to run multiple applications simultaneously on most of the machines.
To maintain uniformity and consistency in the standard GUI there are design rules to be followed such
as:

1. Interface should be kept as simple as possible and consistent.
2. Provide easy access to common applications by keeping the user in mind always.
3. Provide customization control as per user preferences.
4. Communicate the application actions to the user clearly.
Thus, it can be concluded that GUI is a very important component of computer graphics.
1.3 Overview of Image Representation

Every computer has images. Most of them are clear, like icons on buttons and photos on web pages and
some are more restrained. In particular, the great quantity of data in an image means that compression
needs to be used for storing and transmitting that data efficiently.
Images must be represented in an appropriate manner, so that they can be clearly seen and understood.
There are two main types of image representation:
1. Raster Image Representation: A digital image or a normal image is composed of picture elements
or discrete pixels. These pixels are prearranged in a row and column style, to outline a rectangular
picture area. It is sometimes referred to as a Raster. Many images are normally represented as sets
of pixels encoding brightness/color information in the form of a matrix. This type of image
representation is related to the matrix image representation, where every element of the matrix
(pixel) possesses its own value, which corresponds to the brightness of that element. In this matrix
form of image representation, every pixel has a value that is equal to 0 (background), or 1 (object),
which needs one bit per one pixel. Generally, this type of image representation is not used in a
direct manner in the information systems of computer graphics, except for activities, such as
compression, storage, and transmission of information.
2. Vector Image Representation: In this type of image representation, curves or points with vectors
that connect these points are used to represent every graphical object or image.

Apart from raster and vector image representations, images can also be represented using a model that
is based on contour lines.

A contour line is a curve beside which the function has a constant value.

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