Introduction to Computer Graphics

1. Introduction to Computer Graphics

3. What is Computer Graphics? • A computer is a device capable of storing data • in a format suited to the computer, • which is then processed by mathematical manipulation and correlation of data. • Graphics is the way in which data is displayed after the processing has been performed.

4. Reason behind Computer Graphics • The Movie Industry. • Gaming Industry • Medical Imaging and Scientific Visualization • Computer Aided Design

5. Advantages • High quality graphics display. [Win7] • Ability to reproduce not only real-world objects but abstract objects too. [Car design] • Animation • Parameters under our control: Speed, part or full scene view, Geometrical relationship with of the objects in the scene wrt other objects.

6. Advantages Continued… • Builders use CAD for creating walkthroughs to be presented to the clients. • Motion dynamics • Update dynamics • Audio + Video output gives a realistic look.

7. Realism

8. How is the data displayed???

9. Picture Element => Pixel => Pel • The smallest addressable screen element. • A pixel need not represent just a single point. • A pixel rather represents a region which can contain a number of infinite points.

10. What does a pixel contain??? A pixel contains: • Co-ordinates • Intensity • Color

11. Pixel Approximation • Special procedures are required to determine which pixel will provide the best approximation to the desired picture or graphics object. • RASTERISATION • SCAN CONVERSION

12. Types of images • JPEG • Vector • Bitmap • TIFF • ……

13. Vector • In physics, a vector is defined as having magnitude as well as direction. • A vector file is sometimes called a geometric file. • Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon(s), which are all based on mathematical equations, to represent images in computer graphics. [eg: Maps]

14. Vector Graphics • It is the creation of digital images through a sequence of commands or mathematical statements that place lines and shapes in a given 2D or 3Dspace. • The work of a graphics artist’s work is saved as a vector graphic file. • This is eventually converted to bitmap file in order to port it between systems.

15. Advantages of vector graphic • It is not resolution dependent hence scalability (resizing) of the image does not result in loss of image quality. [Logos, maps] • Control points help in resizing the object. • A graphic file does not contain the image itself, rather it contains the mathematical equations.

16. Disadvantages of vector graphic • Drastically minimizing the object may result in the erosion of fine lines but the picture quality remains the same. Too much enlargement can make the mistakes visible. • Although photorealistic look is possible but still most vector images look like sharply drawn cartoon images.

17. Bitmap image • An image made up from individual pixels is often referred to as a bitmap or a pixmap image. • It is a spatially mapped array of bits i.e pixels known as a map-of-bits

18. Bitmap Vector V/s Bitmap Raster images are based on pixels and thus scale with loss of clarity, while vector-based images can be scaled indefinitely without degrading quality.

19. Rasterized bitmap image of a vectorial image

20. QUIZ#1 • Which of the following devices is a graphics device? Printer Keyboard Mouse Joystick Touch Screen LCD

21. Summary • Vector images are a collection of individual objects rather than picture elements. • A vector image can be composed of points connected by lines, or nodes (control points) connected by Bezier curves. • Animation images are also usually created as vector files. Example, Shockwave's Flash product lets you create 2-D and 3-D animations that are sent to a requestor as a vector file and then rasterized "on the fly" as they arrive.

22. Color Depth