Graphics Systems
اسلاید 1: Graphics SystemsDr. S.M. MalaekAssistant: M. Younesi
اسلاید 2: OverviewDisplay HardwareHow are images displayed?
اسلاید 3: Overview (Display Devices)Raster Scan DisplaysRandom Scan DisplaysColor CRT MonirorsDirect View Storage TubeFlat panel DisplaysThree Dimensional Viewing DevicesStereoscopic and Virtual Reality System
اسلاید 4: Overview (Display Devices)The display systems are often referred to as Video Monitor or Video Display Unit (VDU).
اسلاید 5: Display HardwareVideo Display DevicesThe primary output device in a graphics system is a monitor.
اسلاید 6: Video MonitorCathode Ray Tube (CRT)
اسلاید 7: Electron GunsElectron BeamsFocusing CoilsDeflection CoilsAnode ConnectionShadow MaskPhosphor layerClose-up of the phosphor coated inner side of the screen
اسلاید 8: Cathode Ray Tube (CRT)
اسلاید 9: Refresh CRTLight emitted by the Phosphor fades very rapidly.Refresh CRT: One way to keep the phosphor glowing is to redraw the picture repeatedly by quickly directing the electron beam back over the same points.
اسلاید 10: Electron Gun
اسلاید 11: Electron GunHeat is supplied to the cathode by the filament.
اسلاید 12: Electron GunThe free electrons are then accelerated toward the phosphor coating by a high positive voltage.
اسلاید 13: High Positive VoltageA positively charged metal coating on the inside of the CRT envelope near the phosphor screen.A positively charged metal
اسلاید 14: High Positive VoltageAn accelerating anode .
اسلاید 15: Electron GunIntensity of the electron beam is controlled by setting voltage level on the control grid.
اسلاید 16: Electron GunA smaller negative voltage on the control grid simply decrease the number of electrons passing through.
اسلاید 17: Focusing System
اسلاید 18: Focusing SystemThe focusing system is needed to force the electron beam to converge into a small spot as it strikes the phosphor.Electrostatic focusing is commonly used in computer graphics monitor.
اسلاید 19: Focusing SystemWith electrostatic focusing, the electron beam passes through a positively charged metal cylinder that forms an electrostatic lens.
اسلاید 20: Focusing SystemSimilar lens focusing effects can be accomplished with a magnetic field set up by a coil mounted around the outside of the CRT envelope.
اسلاید 21: Focusing SystemThe distance that the electron beam must travel to different points on the screen varies because the radius of curvature for most CRTs is greater than the distance from the focusing system to the screen center.
اسلاید 22: Focusing SystemThe electron beam will be focused properly only at the center of the screen.As the beam moves to the outer edges of the screen, displayed images become blurred.Dynamically focusing lens work based on beam position.
اسلاید 23: Deflection Systems
اسلاید 24: Deflection SystemsDeflection of the electron beam can be controlled either with electric fields or with magnetic fields.The magnetic deflection coils mounted on the outside of the CRT envelope.
اسلاید 25: Deflection SystemsTwo pairs of coils are used, with the coils in each pair mounted on opposite sides of the neck of the CRT envelope.
اسلاید 26: Deflection SystemsOne pair is mounted on the top and bottom of the neck, and the other pair is mounted on opposite sides of the neck.
اسلاید 27: Deflection SystemsHorizontal deflection is accomplished with one pair of coils, and vertical deflection by the other pairs.The proper deflection amounts are attained by adjusting the current through the coil.
اسلاید 28: Deflection SystemsElectrostatic deflection: Two pairs of parallel plates are mounted inside the CRT envelope.
اسلاید 29: Deflection SystemsOne pair of plates is mounted horizontally to control the vertical deflection, and the other pair is mounted vertically to control horizontal deflection.
اسلاید 30: Spots of Light
اسلاید 31: Spots of LightSpots of lights are produces on the screen by the transfer of the CRT beam energy to the phosphor.Part of the beam energy is converted into heat energy.
اسلاید 32: Spots of LightThe excited phosphor electrons begin dropping back to their stable ground state, giving up their extra energy as small quantums of light energy.
اسلاید 33: PersistencePersistence :The time it takes the emitted light from the screen to decay to one-tenth of its original intensity.
اسلاید 34: Intensity DistributionThe intensity is greatest at the center of the spot, and decrease with Gaussian distribution out to the edges of the spot.
اسلاید 35: Resolution (Spots of Light)Resolution: The maximum number of points that can be displayed without overlap on a CRT. Overlap
اسلاید 36: Resolution (Spots of Light)Resolution of a CRT is dependent on:The type of phosphorThe intensity to be displayedThe focusing and deflection systems.Typical resolution: 1280 by 1024
اسلاید 37: Aspect RatioAspect Ratio: This numbers gives the ratio of vertical points to horizontal points necessary to produce equal length lines in both directions on the screen.
اسلاید 38: Electron GunsElectron BeamsFocusing CoilsDeflection CoilsAnode ConnectionShadow MaskPhosphor layerClose-up of the phosphor coated inner side of the electron
اسلاید 39: Cathode Ray Tube (CRT)Electron GunDeflection Coils Electron BeamShadow maskBeam passing through maskAnode Connection
اسلاید 40: Raster Scan Displays
اسلاید 41: Raster Scan DisplaysRaster: A rectangular array of points or dotsPixel: One dot or picture element of the rasterScan Line: A row of pixels
اسلاید 42: Raster Scan DisplaysIn a raster scan system, the electron beam is swept across the screen, one row at a time from top to bottom.
اسلاید 43: Raster Scan DisplaysAs the electron beam moves across each row, the beam intensity is turned on and off to create a pattern of illuminated spots.
اسلاید 44: Raster Scan DisplaysPicture definition is stored in a memory area called the refresh buffer or frame buffer.
اسلاید 45: Raster Scan DisplaysRefresh buffer or frame buffer: This memory area holds the set of intensity values for all the screen points.
اسلاید 46: Raster Scan DisplaysStored intensity values then retrieved from refresh buffer and “painted” on the screen one row (scan line) at a time.
اسلاید 47: Raster Scan DisplaysIntensity range for pixel positions depends on the capability of the raster system.A black-and-white system: each screen point is either on or off, so only one bit per pixel is needed to control the intensity of screen positions.
اسلاید 48: Raster Scan DisplaysOn a black-and-white system with one bit per pixel, the frame buffer is called bitmap.For system with multiple bits per pixel, the frame buffer is called pixmap.
اسلاید 49: Raster Scan DisplaysSometimes, refresh rates are described in unit of cycles per second, or Hertz (HZ)
اسلاید 50: Raster Scan DisplaysRefreshing on raster scan displays is carried out at the rate 60 to 80 frame per second.
اسلاید 51: Raster Scan DisplaysHorizontal retrace: The return to the left of the screen, after refreshing each scan line.
اسلاید 52: Raster Scan DisplaysVertical retrace: At the end of each frame (displayed in 1/80th to 1/60th of a second) the electron beam returns to the top left corner of the screen to begin the next frame.
اسلاید 53: InterlacingOn some raster systems (TV), each frame is displays in two passes using an interlaced refresh procedure.
اسلاید 54: InterlacingOn an older, 30 frame per-second, noninterlaced display, some flicker is noticeable. With interlacing, each of the two passes can be accomplished in 1/60th of a second. An effective technique for avoiding flicker
اسلاید 55: Raster imageThe quality of a raster image is determined by the total number pixels (resolution), and the amount of information in each pixel (color depth)
اسلاید 56: Raster imageRaster graphics cannot be scaled to a higher resolution without loss of apparent quality.
اسلاید 57: Raster imageBrightness and color @ each x, y on screen
اسلاید 58: Random Scan Displays
اسلاید 59: Random Scan DisplaysRandom scan display is the use of geometrical primitives such as points, lines, curves, and polygons, which are all based upon mathematical equation. Raster Scan is the representation of images as a collection of pixels (dots)
اسلاید 60: Random Scan DisplaysIn a random scan display, a CRT has the electron beam directed only to the parts of the screen where a picture is to be drawn.Random scan monitors draw a picture one line at a time (Vector display, Stroke –writing or calligraphic displays).
اسلاید 61: Random Scan DisplaysThe component lines of a picture can be drawn and refreshed.
اسلاید 62: Random Scan DisplaysThe component lines of a picture can be drawn and refreshed.
اسلاید 63: Random Scan DisplaysRefresh rate depends on the number of lines to be displayed.Picture definition is now stored as a line-drawing commands an area of memory referred to as refresh display file (display list).
اسلاید 64: Random Scan DisplaysTo display a picture, the system cycle through the set of commands in the display file, drawing each component line in turn.
اسلاید 65: Random Scan DisplaysRandom scan displays are designed to draw all the component lines of a picture 30 to 60 times each second.
اسلاید 66: Random Scan DisplaysRandom scan displays are designed for line-drawing applications and can not display realistic shaded scenes.
اسلاید 67: Random Scan Displays
اسلاید 68: Random Scan DisplaysRandom scan displays have higher resolution than raster systems.Vector displays product smooth line drawing.Ideal DrawingVector Drawing
اسلاید 69: Random Scan DisplaysA raster system produces jagged lines that are plotted as discrete points sets.RasterOutline primitivesFilled primitives
اسلاید 70: Random Scan ExampleData are describing a circle:the radius rThe location of the center point of the circleStroke line style and colorFill style and color
اسلاید 71: Random Scan ExampleAdvantages:This minimal amount of information translates to a much smaller file size. (file size compared to large raster images)On zooming in, and it remains smoothThe parameters of objects are stored and can be later modified (transformation).
اسلاید 72: Color CRT Monitors
اسلاید 73: Color CRT MonitorsA CRT monitor displays color pictures by using a combination of phosphors that emit different color lights.
اسلاید 74: Methods1. Beam Penetration2. Shadow Mask
اسلاید 75: Beam Penetration Method
اسلاید 76: Beam Penetration MethodTwo layers of phosphor (red and green) are coated onto the inside of the CRT screen.The display color depends on haw far the electron beam penetrates into the phosphor layers.
اسلاید 77: Beam Penetration MethodThe speed of the electrons, and the screen color at any point, is controlled by the beam acceleration voltage.
اسلاید 78: Beam Penetration MethodThe beam penetration method:Used with random scan monitorsOnly four colors are possible (red, green, orange, and yellow).Quality of pictures is not as good as with other methods.
اسلاید 79: Shadow MaskMethod
اسلاید 80: Shadow Mask MethodThe color CRT has:Three color phosphor dots (red, green and blue) at each point on the screenThree electron guns, each controlling the display of red, green and blue light.
اسلاید 81: Shadow Mask MethodDelta Method:In-line Method:
اسلاید 82: Shadow Mask MethodThe delta-delta method:
اسلاید 83: Shadow Mask MethodThe in-line method:
اسلاید 84: Shadow Mask MethodWe obtain color variations by varying the intensity levels of the three electron beam.
اسلاید 85: Shadow Mask MethodShadow mask methods are:Used in raster scan system (including color TV)Designed as RGB monitors.
اسلاید 86: Shadow Mask MethodHigh quality raster graphics system have 24 bits per pixel in the frame buffer (a full color system or a true color system)
اسلاید 87: Color Models
اسلاید 88: The RGB Color ModelR, G, and B represent the colors produced by red, green and blue phosphors, respectively.Gray axis
اسلاید 89: RGB Color ModelRGB color space
اسلاید 90: CMY Color ModelCMY (short for Cyan, Magenta, Yellow, and key) is a subtractive color model.
اسلاید 91: CMY Color Model
اسلاید 92: Color Depth, Bit DepthThe number of discrete intensities that the video card is capable of generating for each color determines the maximum number of colors that can be displayed.The number of memory bits required to store color information (intensity values for all three primary color components) about a pixel is called color depth or bit depth.
اسلاید 93: Color Depth, Bit DepthA minimum of one memory bit (color depth=1) is required to store intensity value either 0 or 1 for every screen pixel.If there are n pixels in an image a total of n bits memory used for storing intensity values (in a pure black & white image)
اسلاید 94: Bit PlaneThe block of memory which stores (or is mapped with) intensity values for each pixel (B& W image) is called a bit plane or bitmap.
اسلاید 95: 3Bit color displayColor or gray levels can be achieved in the display using additional bit planes.
اسلاید 96: N Bit PlanesThe result for n bits per pixel (color depth=n) is a collection of n bit planes (2n colors or gray shades at every pixel)
اسلاید 97: True ColorFor true Color three bytes of information are used, one for each of the red, blue and green signals that make a pixel.A byte can hold 256 different values and so 256 intensities setting are possible for each electron gun which mean each primary color can have 256 intensities (256*256* 256 color possible)
اسلاید 98: High ColorFor high Color two bytes of information are used, to store the intensity values for all three color. This is done by dividing 16 bits into 5 bits for blue, 5 bits for red and 6 bits for green. This means 32(=25) intensities for blue, 32 (=25) for red, and 64 (=26) for green.Loss of visible image quality.
اسلاید 99: 256 color modeThe PC uses only 8 bits, 2 bits for blue and 3 each for green and red.Most of the colors of a given picture are not available.A palette or look-up table is used here.
اسلاید 100: Color PaletteA palette is a separate memory block (in addition to the 8 bit plane) created 256 different colors.Each color is defined using the standard 3 byte color definition that is used in true color.The intensity values for each of the three primary color component can be anything between 0 and 255 in each of the table entries.
اسلاید 101: Color PaletteThe intensity values for each of the three primary color component can be anything between 0 and 255 in each of the table entries.Total number of colors available is called color palette.
اسلاید 102: Raster Scan Systems
اسلاید 103: Raster Scan SystemsIn addition to the central processing unit (CPU), a special processor, called the video controller or display controller, is used to control the operation of the display device.
اسلاید 104: Video ControllerA fixed area of the system memory is reserved for the frame buffer, and the video controller is given direct access to the frame buffer memory.
اسلاید 105: Video ControllerFrame buffer location, and the corresponding screen positions, are referenced in Cartesian coordinates.xy
اسلاید 106: Video ControllerScan lines are then labeled from ymax at the top of the screen to 0 at the bottom. Along each scan line, screen pixel positions are labeled from 0 to xmax.Line Scany maxx maxxyLine Scany maxx max
اسلاید 107: Video ControllerTwo registers are used to store the coordinates of the screen pixels.Raster Scan Generatorx Registery RegisterMemory AddressFrame BufferIntensityThe Basic refresh operation of the video controller.
اسلاید 108: Video ControllerSome of operations can be performed by the Video Controller:Refreshing operationTransformation (Areas of the screen can be enlarged, reduces, or moved during the refresh cycles)
اسلاید 109: Raster Scan Display Processor
اسلاید 110: Raster Scan Display ProcessorA raster system containing a separate display processor (graphics controller, display coprocessor)The purpose of the DP is to free the CPU from the graphics chores.
اسلاید 111: DPA major task of the display processor is Scan Conversion.Scan Conversion: is digitizing a picture definition given in an application program into a set of pixel intensity values for storage in the frame buffer.( scan conversion straight line segment, Character )
اسلاید 112: DPGeneration various line styles (dashed, dotted, or solid)Displaying color areasPerforming certain transformation and manipulation on display objects.
اسلاید 113: Random Scan Systems
اسلاید 114: Random Scan SystemGraphic commands are translated by the graphics package into a display file stored in the system memory.This file is then accessed by the display processor unit (DPU)(graphic controller) to refresh the screen.
اسلاید 115: Raster Scan SystemRandom Scan System
اسلاید 116: Flat Panel Displays
اسلاید 117: Flat Panel DisplaysA class of video devices that have reduce volume and weight compared to a CRT. A significant feature of flat panel displays is that they are thinner than CRTs.
اسلاید 118: Flat Panel DisplaysCurrent uses for flat panel displays:Small TV monitorsCalculatorsPocket video gamesLaptop computersAdvertisement boars in elevators
اسلاید 119: Flat Panel DisplaysFlat panel displays:Emissive or Emitters DisplaysNon-emissive or Non-emitters Displays
اسلاید 120: Emissive (or Emitters) DisplaysEmissive displays convert electrical energy into light.Examples: Plasma panel, thin-film electroluminescent displays, Light-Emitting Diodes (LED) and flat CRT.
اسلاید 121: Non-Emissive (or Non-Emitters) DisplaysUse optical effects to convert sunlight or light from some other source into graphics pattern.Example: Liquid-Crystal Device (LCD)
اسلاید 122: Flat CRT
اسلاید 123: Flat CRTElectron beams are accelerated parallel to the screen, then deflected 90º to the screen.
اسلاید 124: Plasma Panel
اسلاید 125: Plasma PanelA layer of gas (usually neon) is sandwiched between two glass plates.
اسلاید 126: Plasma PanelBy applying high voltage to a pair of horizontal and vertical conductors, a small section of the gas (tiny neon bulb) at the intersection of the conductors break down into glowing plasma of electrons and ions.
اسلاید 127: Thin Film Electroluminescent
اسلاید 128: Thin Film ElectroluminescentThe region between the glass plates is filled with a phosphor, such as zinc sulfide doped with manganese.
اسلاید 129: Light Emitting Diode (LED)
اسلاید 130: Light Emitting Diode (LED)A matrix of diodes is arranged to form the pixel positions in the display, and picture definition is stored in a refresh buffer.Information is read from the refreshed buffer and converted to voltage levels that are applied to the diodes to produce the light patterns in the display.
اسلاید 131: Liquid Crystal Displays (LCD)
اسلاید 132: Liquid Crystal Displays (LCD)Used in small systems, such as calculators, laptop computers.Produce a picture by passing polarized light (from the surrounding or from an internal light source) through a liquid-crystal material that can be aligned to either block or transmit the light.
اسلاید 133: Liquid Crystal Displays (LCD)Liquid crystal: These compounds have a crystalline arrangement of molecules, yet they flow like a liquid.
اسلاید 134: Liquid Crystal Displays (LCD)Two glass plates, each containing a light polarizer at right angles to the other plate, sandwich the liquid crystal materials.Rows of horizontal transparent conductor & columns of vertical conductors (put into glass plates)
اسلاید 135: Liquid Crystal Displays (LCD)Polarized light passing through the material is twisted so that it will pass through the opposite polarizer.The light is then reflected back t the viewer.
اسلاید 136: Liquid Crystal Displays (LCD)
اسلاید 137: Liquid Crystal Displays (LCD)To turn off the pixel, we apply a voltage to the two intersecting conductor to align the molecules so that the light is not twisted.
اسلاید 138: Liquid Crystal Displays (LCD)On StateOff State
اسلاید 139: Exercises?
اسلاید 140: ExercisesDirect View Storage TubesStereoscopic and Virtual Reality System
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