Page 267 - Open Soource Technologies 304.indd

Unit 11: Graphics

Self Assessment Notes

Multiple choice questions:
1. Which one is not an image file format?
(a) GIF (b) JPEG
(c) PNG (d) AIF
2. GIF supports
(a) 100 colours (b) 350 colours
(c) 256 colours (d) None of these

3. In which version of PHP the GD library is inbuilt?
(a) 4.1 (b) 4.2
(c) 4.3 (d) None of these
4. Which version of GD allows true-colour images?
(a) 2.x (b) 1.x
(c) 3.x (d) None of these

11.3 Basic Graphics Concept

Picturing the relationships between two kinds of data is commonly done using points on a
Cartesian plane. In that section, however, only the algebraic characteristics of points in a plane
were realized no graphical results were achieved. This type of support more difficult to achieve
for three reasons:
• first because providing support for drawing on the screen of the computer requires at
least some platform specific abilities,
• second because, although the mathematical model for graphing envisions a coordinate
system employing real numbers, the graphics environment on computers uses discrete
dots, and these are limited in number. This requires some compromises in the visual
presentation,
• third because the number of dots (pixels) available in the vertical and horizontal directions
cannot be known ahead of time, and
• fourth because even in typical mathematical use there is more than one type of coordinate
system.

The underlying graphics user interface supplied by the computer manufacturer, and to which the
compiler vendor will no doubt provide some interface will probably include a number of tools
for indicating points on the screen, drawing lines, curves, and even a few predefined shapes.
As these are quite system dependent, consideration of them.
11.3.1 Discrete Grids—Graphing Pixels
The standard rectangular or Cartesian (named after René Descartes) has two perpendicular real
number lines (axes) which divide the plane into four quadrants. The place where the number
lines cross is the origin (0, 0) and the numbering is positive to the right and up; negative to the
left and down. This abstraction includes the ability to graph a line as a set of continuous points,
including those such as (¼, 1) where the decimal representation continues indefinitely without
repetition or terminating.

LOVELY PROFESSIONAL UNIVERSITY 261