Computer Graphics in details
Computer graphics deals with the generation, representation, manipulation and display of pictures with the aid of a computer. It plays an essential role in a multimedia application. The pictures used in computer graphics can be broadly classified into two types such as.
1. Line drawings
These are drawings and illustrations in the form of 2D and 3D pictures which are created from mathematical representation of simple objects, like lines, circles, arcs etc. Simple object types are used to create complex objects. For example: the picture of a chair can be drawn using lines and arcs. Numerical results obtained from computations can also be transformed to graphics forms, like bar graphs or pie charts, by using simple objects.
The area of computer graphics which deals with this type of pictures is known as generative graphics. Generative graphics is extensively used in creating illustrative diagrams. Two very important applications of generative graphics are CAD (Computer Aided Design) and CAM (Computer aided manufacturing). Now a days CAD packages are extensively used in designing models for aircraft, ship and building structures, layout of printed circuit boards and chemical plant pipelines etc. Based on these drawings, manufacturing information such as parts list, subassembly list etc are automatically generated and used by CAM packages. The greatest advantage of using CAD and CAM packages for such applications is that the design changes may be quickly modified, by immediately creating accurate assembly drawings and associated parts and subassembly lists.
2. Image
These are pictures and photographs which are composed of a collection of pixels (short form of “picture element” which is a unit of measurement across a computer screen).The pixels of an image are arranged as a two-dimensional matrix. This two-dimensional (or spatial) representation is called the image resolution. Since the storage representation of images is a direct translation of the image pixel by pixel, no concept of a line arc or circle exists.
Each pixel consists of three components red(r), green (G) and blue (B).On a display screen each component of a pixel corresponds to a phosphor. A phosphor glows when excited by an electron gun. Various combinations of different RGB intensities produce different colors.
The area of computer graphics which deals with type of pictures is known as Cognitive graphics. Cognitive graphics along with image processing techniques (like image compression and decompression, cleaning of noisy or blurred images, image editing, etc) is extensively used in applications which deal with recognition and classification of pictures. For example an image database containing images of people’s fingerprints is commonly used now a day in criminal investigation. Another similar application is classification of images of ECG pattern and X-rays of different parts of the body, to perform medical diagnosis of patients by using computers.
HARDWARE REQUIREMENTS FOR GRAPHICS
Computer graphics generally involves the following hardware devices :
1. Allocating device(such as a mouse, a joystick or a stylus) attached to a video display terminal along with a drawing software, is often used to directly draw pictures on computer screen from scratch for generative graphics applications.
2. Flatbed or rectangular-coordinate digitizer is also used as an input device for generative graphics applications for inputting existing line (such as a map) to a computer.
3. Scanners (optical scanners, image-scan digitizers etc) are most commonly used as input devices for capturing photographs and drawings as digital images for cognitive graphics applications.
4. Digital Camera - digital images are also captured directly by a digital camera or a frame capture hardware such as a video capture board interfaced to some standard video source, like video camera or video cassette recorder (VCR)
5. Computer screens with graphics display capability are used to display graphics.
6. Laser printers are most commonly used to output graphics in hard copy form.
7. Plotters are also used to output graphics in hard copy form.
SOFTWARE REQUIREMENTS FOR GRAPHICS
The following graphics processing capabilities are highly desirable in a multimedia computer system for better presentation and use of graphics information.
1. Painting or Drawing software
This software allows the user to create graphics from scratch by using a mouse and various simple objects, such as lines, circles and polygons with various supporting colors. It also allows the user to modify and enhance graphic images produced by using a scanner or screen capture software. All these features make this software very useful for creating desired graphics in a multimedia application.
2. Screen capture software
Often we need to incorporate images from computer screen display in some document. Screen capture software packages are used in such cases to capture the display of a computer screen as a graphic image.
3. Clip art
Clip art is a library of commonly used graphic images or objects, such as a personal computer, printer, airplane, telephone, flower, building etc. These images can be directly imported from the library and used in a multimedia application saving the time and effort which might otherwise be required to create or search and capture a similar image object. This is also helpful if one does not have a scanner or some other means of inputting graphics into the computer. A clip art library often provides the facility to add new objects or delete an existing object from the library.
4. Graphics Importing
The task of creating a multimedia application incorporating graphics can often be greatly simplified if the application software can import graphic images in some standard formats. Common graphic formats include BMP, GIF and PCX.
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