Chapter 1


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Chapter 1

  1. 1. CHAPTER 1:-Basic of Computer Graphics Created by : Mr. Krishna g G. Jadhav RLPC Buldhna,,7875075068
  2. 2. INTRODUCTION:-•The term Computer graphics includes almost everything on thecomputers that is not text.•Today‟s we are touch lot‟s of computer generated graphics in ourdaily life. Ex. Weather report on television, newspapers etc.• The computer is called data processing machine, or we can say it is atoo which performs storing, processing and manipulating data. Ex.Performing arithmetic operations and collect and generate dataaccording to user‟s need.•A machine can easily generate hundred lines of code or thousandsentries of table. At this stage Computer graphics very useful, becausereader can‟t understand lines of code. Etc.
  3. 3. DEFINITION:-Computer Graphics is the study of technique to improve thecommunication between human and machine. In above definition:The word computer Graphics means picture, graph, or sceneis drawn with help of computer. Computer Graphics allows communication through pictures, charts and diagrams, as there is old adage “thousand words can be replaced by a single picture.
  4. 4. APPLICATIONS:•Engineering and/Scientific S/W, Business S/W.•T.V. channels, Space simulation training.•PCB designing, map preparation.•User interface, animation.•Making charts, Image processing.•Office automation.•Desktop Publishing.•CAD/CAM•Art & Commerce.•Process Controlling.•‘Visual effects ‘ in movies and Computer Games.
  5. 5. DISPLAY / VIDEO ADAPTERS:A video adapter or display adapter is an integrated circuit card in acomputer that provides digital to analog converter, video RAM and avideo controller so that data can be sent to a computers display.Figure:
  6. 6. Display adapters are characterized by:1. Resolution: it refers to the no. of dots on the screen. It is expressed as a pair of no‟s that give the no. of dots on horizontal line and vertical lines. For example: 640X480,1024X768.•Computer display generates colors by combining amounts ofRed, Green , and blue. these colors are controlled by 3 wires inthe display cable. Each has variable amount of voltagerepresented by a number from 0 to 255. this up to 16 millionpossible colors.
  7. 7. 2. Color Depth:•It is determined by the no. of bits assigned to hold colorvalue. For example: 1 bit= 2 colors(Black & white)4 bits= 16 colors,8 bits= 256 colors,16 bits= 32 thousandscolors,24 bits=16 million (high colors),32 bits= latest(truecolor).The display adapter stores a value (4 to 32 bit) in memory forevery dot on the screen. The amount of storage needed isdetermined by multiplying the no of dots(Resolution) by thememory required for each dot.•For Eg. VGA having resolution 640X480 with 4 bit color 256 KBmemory is required.
  8. 8. 3.Referesh Rate:• It determines the speed of that display uses to paint the dots on the screen. The original VGA display run at 70Hz• A utility program is typically provided on diskette to set the refresh rate on the display adapter for various resolutions.4.Acceleration:• It Can draw lines and boxes, fill background color, scroll text and manage the mouse pointer.• With an accelerator only CPU has to send the video adapter a command to draw lines.( with may include starting ,ending point and width, color of line.• An accelerator card reduces the amount of data that must be transferred between PC & display (video)adapter.
  9. 9. •Modes: Many display adapters support severaldiff. modes of resolution these are:1. Text Mode or Character Mode.2. Graphics Mode.1. Text Mode: this video mode display screen is divided in to rows and columns of boxes. Each box can contained one character. •Including all VGA video standards 25 Rows PC ,Supports a text mode that divides the screen in to 25 rows & 80 Columns. •Display Screen treated as an Array of block. Each can be hold one ASCII Character. 80 columns
  10. 10. 2. Graphics Mode: this video mode display screen is divided in to an array of pixel.1. Pixel is the smallest addressable element screen.2. Each pixel has name or address,so that we can uniquely identify that .3. Programs that run in graphics mode can display an unlimited variety of shapes and fonts, whereas program running in text mode are severely limited.4. Programs that runs entirly in graphics mode are called graphics based programs 480 640
  11. 11.  Graphics Mode function: If we want start graphics programming then we need to files which GRAPHICS.H & GRAPHICS.LIB. These files provided as part of turboc C and C++. The graphics mode function required a graphics monitor and adapter card such as CGA,EGA & VGA.For Eg. /* sample example to draw line*/ #include<stdio.h> #include<graphics.h> void main() { int gd = DETECT,gm; initgraph(&d ,&gm,” C:/tc/bgi”); Line(200,200,100,100); closegraph( ); restorecrtmode( ) ; }
  12. 12.  Graphics Mode function:1) Basic Graphics mode function:-1).initgraph( ):- it is used to initialized graphic mode.Syntax:- initgraph(int gd,intgm, “path”).gd(Graphics Driver):- this is the argument specifies the graphics driver to beused and it interfaces with display adapter. Some available graphics driver areCGA,EGA,VGAgm (Graphics Mode):- Each graphic adapter can use several diff possoble graphicsmodes. The mode argument is used to select particular mode.path:- It specifies path to graphics driver. Graphics drivers are files with BGI fileextensions. The path name is string threfore it must be surrounded by quotes.DETECT : is a macro which automatically select driver.Eg. int gd = DETECT,gm; initgraph(&d ,&gm,” C:/tc/bgi”);2). closegroup( ): it is used to close graphics mode. Closegraph function restores theprevious display mode. Syntax:- closegraph( );
  13. 13.  Graphics Mode function:2) Shapes:- In computer graphics has many inbuilt commands, which can be used either to draw ashape and/or for filling a colour in any bounded shape.1) lineto( ):- This command draws a line on sceen from current cursor positionto the x,y position. Syntax :- lineto(x,y);2) line ( ): this command draws line on screen. Syntax(x1,y1,x2,y2);.3)circle( ):- Draws a cirlce on screen. Syntax:- circle(x,y,r);4) Rectangle( ): draws a rectangle on screen. Syntax rectangle(x1,y1,x2,y2);5) ellipse( ): draws ellipse on screen. Syntax :- ellipse(x,y,start,end,xrad,yrad);x,y are the co-ordinates of center point.Start, end- starting & ending angle of ellipse.xrad,y,rad- x-axis and y axis radious respectively.6) drawpoly( ): It draws outline of polygon having specified no of sides.Syntax:- drawpoly( n,array), where n is no of vertices of polygon.Array is integer array name which stores co-ordinates of vertices of a polygonEg:- drawpoly(4,p), int p[8]=[10,10,40,40,60,60,100,100]
  14. 14.  Text Mode function: We had seen, text mode screen is divided in to characters position. Screen is mapped as no of rows and no of columns,.Graphic function of Text mode:- 1) Window:- This function specifies a window on screen. Syntax:- Window(left,top,right,bottom);2) putch( ): it displays a single character at a cursor position. Eg. putch(„char‟)3) clrscr( ): It clears the entire screen and locates the cursor in top left corner of screen.4) gotoxy( ):- it positions the cursor to the specifies location on screen, where location is specified by the x,y co-ordinates of the point. Syntax(gotoxy(x,y).5) puts( ):- It display string at cursor position. Syntax :- puts(s1);6) textcolor( ):- It sets the color for text. Any text display after this command will be displayed in colour specified by this command. Syntax:- textcolor(color); .Eg. :- int col=2; textcolor(col);
  15. 15. Text mode graphic function supported following colors are no from 0 to 15.Colour Colour Colour Colour Colour Colour Name Color Colourconstant Name const. Name const. const. Name 0 BLACK 5 MAGENTA 10 LIGHTGREEN 15 WHITE 1 BLUE 6 BROWN 11 LIGHTCYAN 2 GREEN 7 LIGHTGRAY 12 LIGHTRED 3 CYAN 8 DARKGRAY 13 LIGHTMAGENTA 4 RED 9 LIGHTBLUE 14 YELLOW7). delline( ):- It deletes a line specified by cursor position. After deletion, allsubsequent line will be pushed up by one line. Eg. gotoxy(4,5); delline( );8) . inline( ):- It insertes a blank line at current cursor position. Eg. gotoxy(4,5);inline();9). textbackground( ):- It changes background colour of text. The valid colour forCGA are from 0 to 6 in above table.10). moveto( ):- It moves cursor to the location specified by int(x,y) co-ordinates.11)outtextxy( ):- It displays text within quation mark at specified location with latestset colour style. Eg. outtextxy(x,y,”sentence”);
  16. 16.  GRAPHICS.H : Header files contains definitions of all the graphic functions and constants. While GRAPHICS.LIB file contains standard graphics function. /* sample example to draw line*/ #include<stdio.h> #include<graphics.h> void main() { int gd = DETECT,gm; init graph(&d ,&gm,” C:/tc/bgi”); Line(200,200,100,100); closegraph( ); restorecrtmode( ) ; }
  17. 17.  Graphics Devices:1. Joysticks: A joystick is nothing but a small vertical lever which is usually called as stick mounted on the base and is used to move the cursor on the screen. It consist of two potentiometers attached to a single lever. As we move the lever, the potentiometer setting get changed and the X and Y coordinates on screen get changed.2. Track ball: Track ball is some sort of an inverted mouse where the ball is held inside the rectangular box. the positioning of the cursor is associated with orientation of the trackball.3. Mouse: (Every one known about the mouse)4. Light pen: Light pen consist of photocell mounted in a pencil like case. It is a pencil shaped device which is used to point a particular position on the screen .
  18. 18.  Graphics Devices:5. Touch panels: Touch panel allow displayed object or screen positions to be selected with a touch of finger.1. Optical touch panels employ a line of infrared light emitting diodes(LED) along one vertical and one Horizontal edge of the frame. The opposite vertical and one horizontal edge contains light detectors. These detectors are used to record which beams are interrupted when the panel is touched. The two crossing beams are interrupted identify the horizontal and vertical coordinates of the screen positioned selected.
  19. 19.  Graphics Devices: •Electron gun generates a6. CRT: basic arrangement of CRT:. beam of electrons which passes through focusing and deflection system and strikes on specified position on phosphor coated screen. When electron beam strikes phosphor that phosphor that phosphor spot emits light and thus the point on screen is visible. •Focusing system makes electron beam extremely finely focused and makes highly concentrated small spot when it Basic Construction of CRT strikes phosphor.othrwise beam will spread when it reaches the screen.
  20. 20. Electron Gun:Electron gun consist of heating fillament,cathode and control grid. whencathode is heated with heating filament inside it by passing current throughfilament, cathode generates electrons.Cathode is surrounded by metal controlgrid with a hole at one end which allows electrons to escape. Intensity ofelectron beam is controlled by setting voltage levels on control grid. A highnegative voltage applied to control grid will shut of beam by repelling andstopping them from passing through small hole at the end of control grid.
  21. 21. •Raster scan CRT:-•In this electron beam moves all over the screen one row at a time.•As electron beam moves across each row, beam intensity is turnedON and OFF to create picture pattern.•Here picture definition is stored in memory called as refresh bufferor frame buffer.•This refresh buffer holds set of intensity values for all screen points.These stored intensity values are tried from buffer and displayed onscreen one row at a time. When beam is moved from left to right, it isON and when moved from right to left it is OFF.
  22. 22. •Raster scan CRT:-•Raster scan may use non-Interlace or interlace technique to displaypicture.• In non-interlaced, electron beam scans through each line by line.•In interlaced techniques, beam firstly scans through even lines andthen odd scan lines thus scanning screen twice, beam scans throughalternated line first and then through remaining alternated lines.Fig. Non-Interlace Fig. Interlace
  23. 23. •Random scan display:-•Random scan display uses the technology to draw directly thepictures on the screen. The beam is displayed on the positions wherethe picture has to be displayed .•Random scan monitors draw a picture one line at a time and for thisreason are also referred to as vector display.•Refresh rate depends on the number of lines to be displayed. Picturedefinition is stored as a set of line drawing commands in an area ofmemory referred to as the refresh display file.Advantages: 1) it has very high resolution and limited only by themonitor.2) In random scan, easy animations are possible.3) It requiresless memory.Disadvantage:- 1)It requires processor controlled beam.2) It cannotdraw a complex image as it has limited density. 3) it is very expensivein terms of color.
  24. 24. •Difference between Raster and Random scan display:-Raster Scan Random Scan•It Stores Information in memory area •It Stores information in memory areacalled refresh buffer or frame buffer called the refresh display file•To display information the electron beam •To display a specified pictured thereturn to the left side of the screen to begin system cycles through the set ofdisplaying the next scan line at the end of command in the display file, drawingeach frame, the electron beam returns to each component line in turn. After allthe top left corner of the screen to begin thenext frame. line drawing commands have been processed, the system cycles back to the first line command in the list.•Scan conversion is not required Scan conversion is required•Scan conversion hardware is not required Scan conversion H/W required.•Cost is low Cost is more•Raster display has abilityto display areas Random scan display draws only linesfilled with solid colours or patterns. and characters.
  25. 25. •Frame Buffer:-•A frame buffer is large contiguous piece of computer memory which is used to store thedisplay image..•The diff kinds of memory used for frame buffers are disk, IC shift registers, drums etc.•To display a pixel on raster display, minimum 1 bit is used in frame buffer for text tomaximum 24 bit in a frame buffer for graphics.•When 1 bit is used to generate a pixel, the picture will be Black and white(0 & 1).•A frame buffer stores information in digital form while raster display requires voltage togenerate pixel. A single bit frame buffer raster CRT display is as following fig. D O A C Electron Gun Information Raster Display Frame buffer DAC:- Digital to Analog Converter
  26. 26. •Frame Buffer Continued:-•If the bits are increased from 1 to n then 2n intensity level can be achieved, for this, all then bits are checked and resulting value is calculated. This value is given to DAC to generateappropriate voltage to set intensity of the pixel on the raster 1 D 0 A C Electron Gun 1 Information 2n Raster Display N Frame buffer DAC:- Digital to Analog Converter
  27. 27. •Rotating memory Frame Buffer Continued:- Drums and diskswere widely used in frame buffers to store the image information.• It is required to be refreshed continuously. Thus, it is necessary to read the disk ordrum again and again to refresh display.•For this the rotating speed is made to coincide with the refresh rate of the screen.•To generate a pixel of desired intensity or colour, it is first necessary to read the disk ordrum.•The information stored in disk or drum is in digital form, hence it is necessary to convertit into analog form using DAC and then this analog signal is used to generate the pixel.•If only one bit is used to generate the pixel then only black and white picture is possible.•Disadvantage:- 1) the cost of the memory is high. 2) It requires more time due to latencyproblem. Disk D or A Drum C Electron Gun Digital Screen Information Analog signal
  28. 28. •Shift register Frame Buffer :- •It is IC, the problem with the rotating memory is that it is slow and expensive while IC- shift register can perform the same task with better speed and is less expensive. •In this circuit, when pulse is applied, the content of memory are shifted by one place removing the last bit and inserting it into the starting bit. •It is rotating the information in a circular form. •In this, one bit of memory is used as an intensity value. •For color or gray scale display more than one IC, shift register can be used in parallel. •Disadvantage: 1.It requires more time due to latency problem.2)In shift-register, even small changes requires more time. 0 0 0 1 1 1 1Direction of Drotation 1 0 1 0 A 0 0 0 C Electron Gun 0 0 0 1 Information Raster Display DAC:- Digital to Analog Converter
  29. 29. •Random Access Frame Buffer :-•Frame buffers are made up of random access circuit, and the color or gray scale of the pixelcan be set by 1,2,4,8 or more bits.•1 bit is generally used in text generation and any simple 2-D graphics figures like square,triangle.•To fill up the graphics figure, 2 to 4 bits of information are required for diff types ofshading effects while 8 or more bits are used for high quality graphics.•In color display 3 guns are used for 3 primary colors .E.g.- Red, Green, Blue, one for each. Red Electron D Gun A R C D G A Green Electron Gun C D BlueElectron B A Gun C Screen Analog signal
  30. 30. •Random Access Frame Buffer continued:-•Another method uses a colour map. The digital information from the frame buffer isconsider as address to a colour map table.•8 bits are used hence it is possible to address 256 colour map table where colour componentis defined with high precision, it gives better results.R G B Red Electron D Gun A R C D G A Green Electron Gun C D BlueElectron B A Gun C Raster Display Analog signal
  31. 31. •Colour CRT Monitor:-•A Color CRT can display colour pictures by using combination ofphosphor that emits diff. coloured lights. Diff. colours are producedby combining emitted color light from diff. phosphor.The two basic techniques used for producing colour display on CRT are:1).Beam Penetration techniques 2).Shadow Mask CRT•1) Beam Penetration Techniques: It is used with random scan monitors. Inthis,normal CRT screen is coated with two phosphor layers. Here redphosphor layer is deposited behind green phosphor layer. A slow electronbeam excites only red phosphor layer and thus produces only red trace. A veryfst beam penetrates through red layer and excites green layers also & thusgives green trace. A beam accelerating voltage controls the speed of beam andhence produces diff. screen colour display.•Drawbacks: 1)Limited Rage of colours are produced.•2). Need to change beam accelerating voltage, which is difficult.
  32. 32. •Shadow Mask CRT :- It Can display much wider range ofcolours than beam penetration techniques.•In this type of CRT a metal plate having small round holes in a triangularpattern call shadow mask is inserted behind phosphor layer. Red spot Green spot Blue spotElectronGun Shadow mask Screen Fig. Shadow mask CRT
  33. 33. •Direct view storage tube(DVST) :- It Consist of twoelectron guns as writing gun & flood gun. Writing gun stores picture patternas a positive charge on storage grid.•This picture pattern is transferred to phosphor by continuous flood ofelectron generated from flood gun.•Flood electrons passes through collector which smoothes out flow ofelectrons. Electrons passes through collector at low speed and are attracted bypositively charged picture pattern on storage grid and are repelled by rest. Flood Electrons Focusing and The attracted electrons by positive defelection system picture pattern pass right through it and strike on phosphor making itFlood gun visible screen. Screen Fig. DVSTElectron WritingGun beam Collector Storage Grid
  34. 34. •Flat panel Display:-•Flat panel display devices are very thinner than CRT.•These display devices have low volume,weight and power requirement ascompared to CRT.There are two types display.•1)Emissive Display:- These devices convert electrical energy into light. Eg.Plasma panels, LED etc.•2)Non-Emissive display:- They use optical effects to converts sunlight or lightfrom some other source in to graphics patterns. E.g. LCD.
  35. 35. •Plasma panels:-•It Consist of two sheets of glass with thin and closed spaced grid electrodesattached to inner faces and covered with dielectric material. These areattached as series of vertical conductors on one glass plate and horizontal onother glass plate.•The space between two glass plate, is filled with neon gas and is sealed. Byapplying voltage between electrodes the gas within panel is divided into tinycells and each cell is independent of it‟s neighbors. firing voltage applied to Horizontal Pair 0f horizontal and conductos/electrodes vertical conductorsGas cause the gas atpanel Glass Plate intersection cell to break down into Cell glowing plasma. Glass Plate vertical conductors /electrodes Fig. Plasma panel Display
  36. 36. •Plasma panels:- contd…•Merits:-•1) light weight,less bulky device.• 2)produces flicker free image.• 3) refreshing is not required.•4) it allows selecting erasing and writing.•Demerits:-•1)poor resolution•2) It needs complex addressing and wiring.• 3) Costly.
  37. 37. •LCD(Liquid crystal Display:- •This display use thread like liquid crystal compounds that tend to keep the long axes of rod shaped molecules aligned. These nematic compounds have crystalline arrangement of molucules,yet they flow like a liquid and hence termed as liquid crystal display. •In following figure, two conductors defines a pixel position. Normally the molecules are aligned as shown in the “On State”TransparentConductor Nematic Liquid crystal •Polarized light passing through the material is twisted so that it will pass through the opposite polarizer. •The light is then reflected back to the viewer. To turn off the pixel, apply a voltage to the two intersecting conductor to alignPolarizer the molecules so that light is not Transparent conductor On State twisted.
  38. 38. •Primitive Operations:-•Most of graphics systems provide basic set of graphic primitive commands.•Graphic primitives are the functions that we use to draw actual lines and thecharacters that make up the picture. These functions provide convenientmethod to application programmer for describing pictures. Basic three mainprimitive functions are:•Move to(x,y):- It used to set the current beam position to (x,y). It moves beamfrom previous current position to (x,y) position without drawing line.•Line to(x,y):- It used to draws line from current beam position to the point(x,y).•Draw text(s):- It used to displays the string „s‟ with its lower left corner atcurrent beam position and reset current beam position to string‟s lower rightcorner.
  39. 39. •Display file Interpreter:-•In raster scan display image information stored in frame buffer. Here frame bufferstores intensity values of all pixel on screen. Whereas in vector refresh display only linecommands necessary to make picture are stored. These line commands are stored in fileis called display file.• Picture image is firstly stored in display file in form of commands and thensome program executes these commands and convert these commands in toactual picture is called display file interpreter, and it serves as interfacebetween graphics program and display device.. User Program Interpreter Display file Display File Fig:- Display file Interpreter
  40. 40. •Display file Structure:-• Display file contains series of commands required to draw a required picture. Thesecommands are made up of two parts as-• i) Operation code(op code) :- Op code identifies what type of command it is andoperands provide co-ordinates of pint(x,y) to process command. Each command needsthree array to store itself in display file. First Array (DF-OP[ ]) stores op code, secondarray (DF- X[ ] ) stores x co-ordinate and third array (DF- Y [ ]) stores y- co-ordinate of apoint. For eg. DF-OP[3], DF- X[3] and DF-Y[3]. Before starting to write a series ofcommands we shall assign come op codes to commands. We consider here only twocommands LINE and MOVE. Lets define OP code 1 for MOVE and 2 for LINE.•ii) Operands. DF-OP DF-X DF-Y 1 3 3 2 3 3 1 10 10 2 10 10 Fig:- Display file Structure
  41. 41. •Graphics File Format:-1. TIFF( Tagged Image File Format): it is a flexible,adaptable file format for handling images and data within a single file, by including the header tags (size definition etc.) defining the image‟s geometry.• A TIFF file also include a vector-based clipping path (outlines,cropping,image frames).• A TIFF file a useful image archive,because,unlike standard JPEG files, a TIFF file using lossless compression may be edited and re-saved without losing image quality.• A TIFF file is a sequences of 8 bit bytes where bytes are numbered from 0 to N.• Advantage:- 1) it is platform independent 2) It is independent of computer system also.• 3) It is versatile and flexible. 4) It supports many compression schemes. 5) It supports additional information about images.• Disadvantage:- 1) It does not support multiple images in one file. 2) Complex file format. 3) It is open ended format, hence programmer can make changes
  42. 42. 2) PCX:•It is developed by ZSOFT for its PC Paintbrush program. PCX is a widelyused format for storing images.•It is graphics file format for graphics programs running on PC‟s. It issupported by most optical scanners, fax programs, and desktop publishingsystems. Files in the PCX format end with a “.pcx”•The PCX is a device-independent raster image format. The file header storesinformation about the display hardware(screen resolution, color depth andpalette information. Etc.) separately from the actual image information,allowing the image to be properly transferred and displayed on computersystems with diff. hardware.•Advantages:- It is most widely used bitmap image format.•Disadvantage:- 1)It has no provision for gray scale image.2) No provision forany colour made other than RGB. 3) does not support other platform.
  43. 43. 2) JPEG (Joint Photographic Expert (Group):•Image files that employ JPEG compression are commonly called “JPEG files”.•JPEG is a lossy compression techniques in which some amount of data is lost.•Lossy compression technologies attempt to eliminate redundant or unnecessaryinformation although it can reduce file sizes to about 5 % of their normal size,some detail is lost in the compression.•JPEG/JFIF is the format most used for storing and transmitting photographicon the world wide web. For this application, JPEG/JFIF is far superior to GIF.•The JPEG compression algorithm is not as well suited for line drawings andother textual or iconic graphics.•Advantages:- 1) suitable for photographic images.2) Reduces file size•Disadvantage:- 1) Some information of image is lost.
  44. 44. 2) GIF(Graphic Interchange Format):•It is simple, memory efficient and back bitmap format.•It can be used with most bitmap editing programs. It compresses BMP files tomuch smaller size.•It sotres Image and other relevant information in sequence of blocks and subblocks where each sub-block has diff function regarding image information,colour, brightness and data compression.•This GIF allows high-quality,high-resolution graphics to be displayed on avariety of graphics h/w and is intended as an exchange and display mechanismfor graphics images.•Advantages:- 1) It gives compact file format.2) provids the option to specifyhow many colours should be saved. 3) allows multiple image to be stored in asingle file. 4) suitable and are popular in Internet and Intranet. 5) It is deviceindependent. 6) It is operating System Independent.•Disadvantage:- 1)Decompression of GIF data is slow.2) It uses only palettecolour. 3) It do not provide other RGB colour and Gray scale.
  45. 45. 2) BMP (Bitmap):•It is default format used by MS- windows. Here, storing and manipulation ofpixels is done with their location and attributes by bit coding method.•In this information is stored in Device-Independent- Bitmap format.•Information can be displayed on any display device. It uses BMP as default fillextension.•The default filename extension of windows DIB file is BMP.•BMP Structure:- It Contains a bitmap-file header, a bitmap-informationheader, a colour table, and an array of bytes that defines the bitmap bits.BITMAPFILEHEADER bmfh;BITMAPINFOHEADER bmih;RGBQUAD aColors[ ];BYTE aBitmapBits[ ];•Advantages:- 1) Simple to use. 2) It is display device independent.•Disadvantage:- 1). Large file size 2) though display device independent theyare limited to window platform. 3) can not store multiple images in one file.
  46. 46. •Co –ordinate System:- •In 2D any point is address by it x & y co- ordinates like fig a. where x co-ordinate is1. Cartesian co-ordinate system:- distance of point from origin measured along x direction and y co-ordinate is distance of a point y from origin measured along y direction & where x & Y are perpendicular to each other. •In 3D Any point is addressed by its x,y,z co ordinates as fig. b. p •Here in 2D & 3 D a line joining origin O to point P a radius vector. x o y y p x p o xz
  47. 47. • Polar Co –ordinate System:- 1.:- 900 1350 450 001800 2250 2700
  48. 48. We will meet Next Chapter Line Circle And PolygonYou can give Feedback to me:-