The hardwares devices used for the computer graphics are
Input Devices: Keyboard, Mouse, Data tablet, Scanner, Light pen, Touch screen, Joystick
Output Devices: Raster Devices- CRT, LCD, LED, Plasma screens, Printers,Vector Devices- Plotters, Oscilloscopes
Trlation is the process of changing the position of an object in a straight-line path from one coordinate location to another. Every point (x , y) in the object must under go a displacement to (x|,y|). the trformation is:x| = x + tx ; y| = y+ty
The point is a most basic graphical element & is completely defined by a pair of user coordinates (x, y).
Run length encoding is a compression technique used to store the intensity values in the frame buffer, which stores each scan line as a set of integer pairs. One number each pair indicates an intensity value, and second number specifies the number of adjacent pixels on the scan line that are to have that intensity value.
A 2-D rotation is done by repositioning the coordinates along a circular path, in the x-y plane by making an angle with the axes. The trformation is given by:X| = r cos (q + f) and Y| = r sin (q + f).
Features of inkjet printers are
@They can print 2 to 4 pages per minute.
@resolution is about 360d.p.i. Therefor better print quality is achieved.
@The operating cost is very low. The only part that requires replacement is ink cartridge.
@Four colors cyan, yellow, magenta, black are available.
The shearing trformation actually slants the object along the X direction or the Y direction as required. ie; this trformation slants the shape of an object along a required plane.
Impact printer press formed character faces against an inked ribbon on to the paper. A line printer and dot-matrix printer are examples. on-impact printer and plotters use Laser techniques, inkjet sprays, Xerographic process, electrostatic methods and electro thermal methods to get images onto the papers. Examples are: Inkjet/Laser printers.
Following are the advantages of electrostatic plotters-
@They are faster then pen plotters and very high quality printers.
@Recent electrostatic plotters includes a scan conversion capability.
@color electrostatic plotters are available. They make multiple passes over the paper to plot color picture.
Following are the differences between vector and raster graphics-
@Raster or Bitmap images are resolution dependent because of this its not possible to increase or decrease their size without sacrificing on image quality.
While vector based image are not dependent on resolution. The size of vector image image can be increased or decreased without affecting image quality.
@Raster or bitmap images are always rectangular in shape, Vector image, however, can have any shape.
@Unlike raster image, vector image can’t be use for realistic images. This is because vector images are made up of solid color areas and mathematical gradients, so they can’t be used to show continuous tones of a colors in a natural photograph.
The reflection is actually the trformation that produces a mirror image of an object. For this use some angles and lines of reflection.
Computer graphics remains one of the most existing and rapidly growing computer fields. Computer graphics maybe defined as a pictorial representation or graphical representation of objects in a computer.
The time it takes the emitted light from the screen to decay one tenth of its original intensity is called as persistence.
The line type, width and color are the attributes of the line. The line type include solid line, dashed lines, and dotted lines.
The merits and demerits of the Penetration techniques areas follows. It is an inexpensive technique. It has only four colors. The quality of the picture is not good when it is compared to other techniques. It can display color sc in monitors. Poor limitation etc.
Properties of video display devices are persistence ,resolution, and aspect ratio.
In the CRT, heat is applied to the cathode by directing a current through a coil of wire, is called filament
A line is of infinite extent can be defined by an angle of slope q and one point on the line P=P(x,y). This can also be defined as y=mx+C where C is the Y intercept.
The ratio of vertical points to the horizontal points necessary to produce length of lines in both directions of the screen is called the Aspect ratio. Usually the aspect ratio is ¾.
Pixel is shortened forms of picture element. Each screen point is referred to as pixel or pel.
Some system has only one bit per pixel; the frame buffer is often referred to as bitmap.
X shear, y shear.
A point (4,3) is rotated counterclockwise by an angle of45°. Find the rotation matrix and the resultant point
In raster scan display, at the end of one frame, the electron beam returns to the left top corner of the screen to start the next frame.
In raster scan display, the electron beam return to the left of the screen after refreshing each scan line, is called horizontal retrace of the electron beam.
The merits and demerits of direct view storage tubes[DVST] are as follows. It has a flat screen. Refreshing of screen is not required. Selective or part erasing of screen is not possible. It has poor contrast Performance is inferior to the refresh CRT.
In computer graphic, image scaling is the process of resizing a digital image. scaling is a non-trivial process that involves a trade off between efficiency, smoothness and sharpness. With bitmap graphics, as the size of an image is reduced or enlarged, the pixels which comprise the image become increasingly visible, making the image appear “soft” if pixels are averaged, or jagged if not.
A 2-D rotation is done by repositioning the coordinates along a circular path, in the x-y plane by making an angle with the axes. The trformation is given by:X| = r cos (q + f) and Y| = r sin (q + f).
The process of adjusting intensities of the pixels along the line to minimize the effect of aliasing is called ant aliasing.
The term computer graphics include almost every thing on computer that is not text or sound. It is an art of drawing pictures, lines. charts, etc. using computers with the help of programming. Or we can say that graphics is the representation and manipulation of image data by computer with the help from specialized software and hardware. Graphic designing is done using the various available softwares for computers which can produce the 3D images in the required shape and dimension. Computer graphics help us in getting the real display experiences.
When a key is pressed on the keyboard, the keyboard controller places a code carry to the key pressed into a part of the memory called as the keyboard buffer. This code is called as the scan code.
Trformation is the process of introducing changes in the shape size and orientation of the object using scaling rotation reflection shearing & trlation etc.
Merits. Refreshing is not required. Produce a very steady image free of Flicker. Less bulky than a CRT. Demerits. Poor resolution of up to 60 d.p.i. It requires complex addressing and wiring. It is costlier than CRT.
The maximum number of points that can be displayed without overlap on a CRT is referred to as the resolution.
Picture definition is stored in a memory area called frame buffer or refresh buffer.
Circle is defined by its center xc, yc and its radius in user coordinate units. The equation of the circle is (x-xc) + (yyc)= r2.
The emissive display converts electrical energy into light energy. The plasma panels, thin film electro-luminescent displays are the examples. The Non-emissive are optical effects to convert the sunlight or light from any other source to graphic form. Liquid crystal display is an example.
Some system has multiple bits per pixel, the frame buffer is often referred to as pix map.
Point clipping, line clipping, area clipping, text clipping and curve clipping.
Video controller is used to control the operation of the display device. A fixed area of the system is reserved for the frame buffer, and the video controller is given direct access to the frame buffer memory.
The Raster and Vector graphics can be explained as-
RASTER- In computer graphics image, or BITMAP, is a dot matrix data structure representing a generally rectangular grid of pixels or points of color, viewable via a monitor, paper, or other display medium. Raster image are stored in image files with varying formats.
VECTOR- Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical expressions, to represent image in computer graphics. “Vector”, in this context, implies more than a straight line.
Four input devices are keyboard, mouse, image scanners, and trackball.
Random scan is a method in which display is made by electronic beam, which is directed only to the points or parts of the screen where picture is to be drawn.
The Raster scan system is a scanning technique in which the electron sweep from top to bottom and from left to right. The intensity is turned on or off to light and un-light the pixel.
A major task of the display processor is digitizing a picture definition given in an application program into a set of pixel-intensity values for storage in the frame buffer. This digitization process is called scan conversion.
In plasma panel display, the region between two glass plates is filled with neon gas. In thin film electroluminescent display, the region between two glasses plates are filled with phosphor, such as zinc sulphide doped with manganese.
The process of determining the appropriate pixels for representing picture or graphics object is known as rasterization.
Beam penetration method, shadow mask method.
A special purpose processor, which is used to control the operation of the display device, is known as video controller or display controller.
Following are the applications of computer graphic
@computer graphics is used in the field of computer aided design.
@It is used to produce illustrations for reports or to generate slide for with projections.
@Computer graphic methods are widely used in both fine are and commercial are applications.
@The artist uses a combination of 3D modeling packages, texture mapping, drawing programs and CAD software.
@In the field of entertainment CG methods are now commonly used in making motion pictures. music videos and television shows.
@Computer-generated models of physical, financial and economic systems are often used as educational aids.