This document provides an overview of video display devices and color graphics technologies. It discusses raster scan displays, which refresh the screen by sweeping the electron beam across rows of pixels stored in a frame buffer. Random scan displays direct the electron beam only where needed to draw lines, allowing higher resolution but not realistic images. Color CRT monitors use shadow mask or beam penetration methods, with the former allowing a wider range of colors by exciting red, green, and blue phosphor dots. Flat panel displays are thinner than CRTs and being used in more portable applications.
The document summarizes video display devices, specifically cathode ray tubes (CRTs). It describes the basic design of CRTs including the electron gun, phosphor coating, and refresh process. CRTs use an electron beam directed by deflection systems to illuminate spots on the screen in a raster pattern, maintained by refreshing the screen rapidly. Color CRTs employ different color phosphors and methods like beam penetration or shadow masks to combine colors. Random scan displays draw images as lines rather than pixels.
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The document summarizes key differences between vector scan and raster scan displays. Vector scan displays directly draw lines between points by moving the electron beam between endpoints, while raster scan displays sweep the beam across the entire screen in lines from top to bottom. Raster scan is more common as it does not flicker even with complex images and has lower cost and hardware requirements than vector scan. Both methods store images in a frame buffer but raster scan must convert graphics to pixels while vector scan does not.
The document discusses various types of raster images and display technologies. Raster images represent pictures as a grid of pixels stored as numerical values. Grayscale images vary pixel depth to generate different colors. Color images use three values per pixel. Display technologies discussed include CRTs, LCDs, plasma displays, and other emissive and non-emissive displays. CRTs use electron guns and phosphors to generate images while LCDs use liquid crystals and polarized light.
Raster scan displays work by sweeping an electron beam across the screen one row at a time, turning the beam on and off to illuminate spots and form an image. The intensity values for each screen point are stored in a refresh buffer and then retrieved to paint the image on the screen. Refresh rates are typically 60-80 frames per second. Random scan displays draw images using geometric primitives and store picture definitions as drawing commands in a refresh display file. Color CRT monitors use either beam penetration or a shadow mask method to display color images by emitting light from red, green, and blue phosphor dots.
This document provides information about different types of display devices used in computer graphics. It discusses cathode ray tubes (CRTs) which produce images using an electron beam striking a phosphorescent screen. CRTs are bulky and electromagnetic fields may pose health risks. Raster scan displays redraw images by sweeping an electron beam across the screen in lines. Color CRTs use phosphors and shadow masks to produce colors. Flat panel displays like liquid crystal displays are thinner alternatives to CRTs.
The document summarizes video display devices, specifically cathode ray tubes (CRTs). It describes the basic design of CRTs including the electron gun, phosphor coating, and refresh process. CRTs use an electron beam directed by deflection systems to illuminate spots on the screen in a raster pattern, maintained by refreshing the screen rapidly. Color CRTs employ different color phosphors and methods like beam penetration or shadow masks to combine colors. Random scan displays draw images as lines rather than pixels.
Do Not just learn computer graphics an close your computer tab and go away..
APPLY them in real business,
Visit Daroko blog for real IT skills applications,androind, Computer graphics,Networking,Programming,IT jobs Types, IT news and applications,blogging,Builing a website, IT companies and how you can form yours, Technology news and very many More IT related subject.
-simply google:Daroko blog(professionalbloggertricks.com)
• Daroko blog (www.professionalbloggertricks.com)
• Presentation by Daroko blog, to see More tutorials more than this one here, Daroko blog has all tutorials related with IT course, simply visit the site by simply Entering the phrase Daroko blog (www.professionalbloggertricks.com) to search engines such as Google or yahoo!, learn some Blogging, affiliate marketing ,and ways of making Money with the computer graphic Applications(it is useless to learn all these tutorials when you can apply them as a student you know),also learn where you can apply all IT skills in a real Business Environment after learning Graphics another computer realate courses.ly
• Be practically real, not just academic reader
The document summarizes key differences between vector scan and raster scan displays. Vector scan displays directly draw lines between points by moving the electron beam between endpoints, while raster scan displays sweep the beam across the entire screen in lines from top to bottom. Raster scan is more common as it does not flicker even with complex images and has lower cost and hardware requirements than vector scan. Both methods store images in a frame buffer but raster scan must convert graphics to pixels while vector scan does not.
The document discusses various types of raster images and display technologies. Raster images represent pictures as a grid of pixels stored as numerical values. Grayscale images vary pixel depth to generate different colors. Color images use three values per pixel. Display technologies discussed include CRTs, LCDs, plasma displays, and other emissive and non-emissive displays. CRTs use electron guns and phosphors to generate images while LCDs use liquid crystals and polarized light.
Raster scan displays work by sweeping an electron beam across the screen one row at a time, turning the beam on and off to illuminate spots and form an image. The intensity values for each screen point are stored in a refresh buffer and then retrieved to paint the image on the screen. Refresh rates are typically 60-80 frames per second. Random scan displays draw images using geometric primitives and store picture definitions as drawing commands in a refresh display file. Color CRT monitors use either beam penetration or a shadow mask method to display color images by emitting light from red, green, and blue phosphor dots.
This document provides information about different types of display devices used in computer graphics. It discusses cathode ray tubes (CRTs) which produce images using an electron beam striking a phosphorescent screen. CRTs are bulky and electromagnetic fields may pose health risks. Raster scan displays redraw images by sweeping an electron beam across the screen in lines. Color CRTs use phosphors and shadow masks to produce colors. Flat panel displays like liquid crystal displays are thinner alternatives to CRTs.
Raster scan systems work like a television, using an electron beam to sweep horizontally across phosphors on the screen. As the beam reaches the right side, it retraces to the left before moving down to the next line. It paints every other line interlaced to refresh the screen 30 times per second. Progressive scan paints every line 60 times per second to reduce flicker, as used in computer monitors. Random scan directly draws points and lines in any order controlled by a display processor reading coordinates, allowing for high resolution, animation, and minimal memory use, but requiring an intelligent beam and limited screen density.
Video monitors use cathode ray tubes to display output. In a cathode ray tube, an electron gun fires a beam of electrons that is focused and deflected to hit phosphor on the screen, causing it to glow. The beam rapidly redraws the image to keep the screen illuminated, in a process called refresh. Key components of the electron gun include a heated cathode that emits electrons, an accelerating anode that speeds up the electrons, and control and focusing systems that shape the beam. When electrons hit phosphor, their energy causes the phosphor to glow briefly.
The document discusses different types of graphics display systems including raster scan displays, random scan displays, and flat panel displays. It describes the key components of cathode ray tube (CRT) displays such as the electron gun and phosphor screen and how they generate images. It also covers color reproduction methods for CRTs like beam penetration and three color guns.
This document discusses computer graphics hardware concepts related to video display devices and input/output devices. It describes the components and operation of cathode ray tube (CRT) displays, including the electron gun, accelerating anode, focusing system, deflection system, and phosphor screen. It also covers raster scan displays, random scan displays, color CRT monitors, and flat panel displays such as plasma panels, thin-film electroluminescent displays, and liquid crystal displays (LCDs). Input devices discussed include keyboards, mice, trackballs, joysticks, digitizers, and image scanners. Output devices covered are printers, including dot matrix, laser, inkjet, and bubble jet printers.
Video display devices use various technologies to visually present electronic information. Common types include CRT, LCD, LED, and plasma displays. CRTs use an electron gun to excite phosphors on the screen and were widely used in monitors and TVs. They can operate in raster or random scan modes. Color CRTs use shadow mask or beam penetration methods. Flat panel displays like LCDs are thinner than CRTs and use light modulation rather than emission to display images.
COLOR CRT MONITORS IN COMPUTER GRAPHICSnehrurevathy
1. Color CRT displays use phosphors and one of two methods - beam penetration or shadow mask - to generate colors.
2. The beam penetration method uses red and green phosphors and electron beam speed to produce four colors, while the shadow mask method uses three color phosphors and electron beam deflection through a shadow mask to generate millions of colors.
3. Flat panel displays like LCDs and plasma panels provide alternatives to CRTs with reduced size and power use, though early types had limitations in features like color capability.
This document summarizes computer graphics and display devices. It discusses that computer graphics involves displaying and manipulating images and data using a computer. A typical graphics system includes a host computer, display devices like monitors, and input devices like keyboards and mice. Common applications of computer graphics include GUIs, charts, CAD/CAM, maps, multimedia, and more. Display technologies discussed include CRT monitors, LCD panels, and other devices. Key aspects of CRT monitors like refresh rate, resolution, and bandwidth are also summarized.
The document discusses different types of display devices including CRT and plasma display panels. CRT uses an electron gun to direct an electron beam at phosphorescent dots on a screen to display images. Color CRT monitors use three electron guns and a shadow mask to activate red, green, or blue phosphor dots to produce color. Plasma display panels contain two glass plates separated by a gas that is electrically excited into plasma to stimulate phosphors and emit light for each pixel.
Raster scanning is used in television and involves scanning an image by rows from left to right using a beam. Each point is called a pixel and pixels are stored in a frame buffer along with their color. A video controller scans each line from left to right and then moves to the next line, accessing the frame buffer to retrieve pixel coordinates and colors. Interlacing was used in older TVs and involved scanning alternating lines to reduce flicker at lower refresh rates. The quality of a raster image depends on its resolution and color depth. Raster scanning requires little memory and is less costly than alternatives but images can lose detail when scaled up due to fixed pixel sizes.
The document describes various types of computer display devices and their characteristics. It discusses raster and random scan displays, CRT monitors, color CRT technologies including beam penetration and shadow mask methods, and other display types such as direct view storage tubes. Input devices are also covered, including keyboards, mice, digitizers, and touch screens.
Raster scan systems use a video controller to refresh the screen by accessing pixels stored in a frame buffer in memory. The video controller uses two registers to iterate through each pixel location, retrieving the pixel value and using it to set the intensity of the CRT beam. It draws one scan line at a time from top to bottom until the entire screen is refreshed at a rate of 60 frames per second. Display processors can offload graphics processing tasks from the CPU by performing operations like scan conversion and generating lines and color areas to draw objects in the frame buffer.
This document provides information about different types of display devices used in computer graphics. It discusses cathode ray tube (CRT) displays, including how CRTs work using an electron gun and accelerating electrons to excite phosphors to emit light. It describes raster scan displays, which draw images as a grid of pixels by sweeping an electron beam across the screen, and random scan displays, which draw images line by line. The document also covers color CRT displays using beam penetration or a shadow mask to combine red, green, and blue phosphors at each pixel location.
presentation By Daroko blog-where IT learners Apply skills.
This topic an presentation will introduce you to Computer graphics hardware types.
---------------------------------
• Daroko blog (www.professionalbloggertricks.com)
• Presentation by Daroko blog, to see More tutorials more than this one here, Daroko blog has all tutorials related with IT course, simply visit the site by simply Entering the phrase Daroko blog (www.professionalbloggertricks.com) to search engines such as Google or yahoo!, learn some Blogging, affiliate marketing ,and ways of making Money with the computer graphic Applications(it is useless to learn all these tutorials when you can apply them as a student you know),also learn where you can apply all IT skills in a real Business Environment after learning Graphics another computer realate courses.ly
• Be practically real, not just academic reader
Do Not just learn computer graphics an close your computer tab and go away..
APPLY them in real business,
Visit Daroko blog for real IT skills applications,androind, Computer graphics,Networking,Programming,IT jobs Types, IT news and applications,blogging,Builing a website, IT companies and how you can form yours, Technology news and very many More IT related subject.
-simply google:Daroko blog(professionalbloggertricks.com)
Raster scan displays work by sweeping an electron beam across the screen one row at a time from top to bottom, turning the beam's intensity on and off to create illuminated spots. This allows the display to store an entire frame of picture data in a frame buffer memory. Raster scanning is well suited for realistic scenes like television and refreshes at 60-80 frames per second. Random scan displays direct the electron beam only where a picture element needs to be drawn, storing pictures as a set of line drawing commands rather than a frame buffer. It is better for applications like plotters that draw individual lines.
The document describes the components and operation of a raster scan graphics display system. A video controller accesses a frame buffer in system memory to refresh the screen. It performs operations like retrieving pixel intensities from different memory areas and using two frame buffers to allow refreshing one screen while filling the other for animation. A raster scan display processor can digitize graphics into pixel intensities for storage in the frame buffer to offload this processing from the CPU.
This document provides an overview of computer graphics hardware and software. It defines computer graphics as using a computer to define, store, manipulate, interrogate and present pictorial output. The key hardware components discussed are display devices like CRT, LCD, and plasma displays. Software components include rendering primitives, algorithms for transformation and rasterization, and application programming interfaces that provide access to graphics hardware. The graphics rendering pipeline is described as the process of converting a 3D scene model into a 2D image through steps like modeling transformations, viewing transformations, projection, clipping and rasterization.
This document summarizes different types of display devices, including cathode ray tubes (CRTs), raster scan displays, random scan displays, liquid crystal displays (LCDs), and light emitting diodes (LEDs). It describes the basic components and functioning of CRTs, including electron guns, phosphor coatings, and deflection coils. It compares raster and random scan displays, noting that raster displays are better for realistic images while random scans are suited for line drawings. LCDs use polarized light passing through liquid crystals to turn pixels on and off. LED displays use semiconductors to emit light when forward biased, and have advantages over traditional light sources like lower energy use and longer lifetimes.
Introduction to computer graphics part 1Ankit Garg
This document discusses computer graphics systems and their components. It describes video display devices like CRTs and how they work. Color is generated using techniques like beam penetration and shadow masks. Raster scan and random scan displays are covered. Input devices for graphics like mice, tablets, and gloves are also summarized. The document provides details on graphics hardware like frame buffers, refresh rates, and video controllers.
This document provides an overview of graphics display systems. It discusses the basic components and operation of cathode ray tube (CRT) displays, including the electron gun, focusing and deflection systems. It describes the refresh process of raster-scan CRTs and how random-scan CRTs work. Color CRT monitors are discussed, specifically the beam penetration and shadow mask methods. Key characteristics like resolution, persistence and aspect ratio are also summarized.
CG03 Random Raster Scan displays and Color CRTs.ppsxjyoti_lakhani
The document discusses different types of graphics displays. It describes raster-scan displays, which use an electron beam that sweeps across the screen from top to bottom to display an image. Picture definition is stored in a frame buffer. It also describes random-scan displays, which direct the electron beam only where lines need to be drawn. Color CRT monitors use phosphors and a shadow mask to display color. Flat panel displays like plasma panels, thin-film electroluminescent displays, and liquid crystal displays provide thinner alternatives to CRTs.
Raster scan systems work like a television, using an electron beam to sweep horizontally across phosphors on the screen. As the beam reaches the right side, it retraces to the left before moving down to the next line. It paints every other line interlaced to refresh the screen 30 times per second. Progressive scan paints every line 60 times per second to reduce flicker, as used in computer monitors. Random scan directly draws points and lines in any order controlled by a display processor reading coordinates, allowing for high resolution, animation, and minimal memory use, but requiring an intelligent beam and limited screen density.
Video monitors use cathode ray tubes to display output. In a cathode ray tube, an electron gun fires a beam of electrons that is focused and deflected to hit phosphor on the screen, causing it to glow. The beam rapidly redraws the image to keep the screen illuminated, in a process called refresh. Key components of the electron gun include a heated cathode that emits electrons, an accelerating anode that speeds up the electrons, and control and focusing systems that shape the beam. When electrons hit phosphor, their energy causes the phosphor to glow briefly.
The document discusses different types of graphics display systems including raster scan displays, random scan displays, and flat panel displays. It describes the key components of cathode ray tube (CRT) displays such as the electron gun and phosphor screen and how they generate images. It also covers color reproduction methods for CRTs like beam penetration and three color guns.
This document discusses computer graphics hardware concepts related to video display devices and input/output devices. It describes the components and operation of cathode ray tube (CRT) displays, including the electron gun, accelerating anode, focusing system, deflection system, and phosphor screen. It also covers raster scan displays, random scan displays, color CRT monitors, and flat panel displays such as plasma panels, thin-film electroluminescent displays, and liquid crystal displays (LCDs). Input devices discussed include keyboards, mice, trackballs, joysticks, digitizers, and image scanners. Output devices covered are printers, including dot matrix, laser, inkjet, and bubble jet printers.
Video display devices use various technologies to visually present electronic information. Common types include CRT, LCD, LED, and plasma displays. CRTs use an electron gun to excite phosphors on the screen and were widely used in monitors and TVs. They can operate in raster or random scan modes. Color CRTs use shadow mask or beam penetration methods. Flat panel displays like LCDs are thinner than CRTs and use light modulation rather than emission to display images.
COLOR CRT MONITORS IN COMPUTER GRAPHICSnehrurevathy
1. Color CRT displays use phosphors and one of two methods - beam penetration or shadow mask - to generate colors.
2. The beam penetration method uses red and green phosphors and electron beam speed to produce four colors, while the shadow mask method uses three color phosphors and electron beam deflection through a shadow mask to generate millions of colors.
3. Flat panel displays like LCDs and plasma panels provide alternatives to CRTs with reduced size and power use, though early types had limitations in features like color capability.
This document summarizes computer graphics and display devices. It discusses that computer graphics involves displaying and manipulating images and data using a computer. A typical graphics system includes a host computer, display devices like monitors, and input devices like keyboards and mice. Common applications of computer graphics include GUIs, charts, CAD/CAM, maps, multimedia, and more. Display technologies discussed include CRT monitors, LCD panels, and other devices. Key aspects of CRT monitors like refresh rate, resolution, and bandwidth are also summarized.
The document discusses different types of display devices including CRT and plasma display panels. CRT uses an electron gun to direct an electron beam at phosphorescent dots on a screen to display images. Color CRT monitors use three electron guns and a shadow mask to activate red, green, or blue phosphor dots to produce color. Plasma display panels contain two glass plates separated by a gas that is electrically excited into plasma to stimulate phosphors and emit light for each pixel.
Raster scanning is used in television and involves scanning an image by rows from left to right using a beam. Each point is called a pixel and pixels are stored in a frame buffer along with their color. A video controller scans each line from left to right and then moves to the next line, accessing the frame buffer to retrieve pixel coordinates and colors. Interlacing was used in older TVs and involved scanning alternating lines to reduce flicker at lower refresh rates. The quality of a raster image depends on its resolution and color depth. Raster scanning requires little memory and is less costly than alternatives but images can lose detail when scaled up due to fixed pixel sizes.
The document describes various types of computer display devices and their characteristics. It discusses raster and random scan displays, CRT monitors, color CRT technologies including beam penetration and shadow mask methods, and other display types such as direct view storage tubes. Input devices are also covered, including keyboards, mice, digitizers, and touch screens.
Raster scan systems use a video controller to refresh the screen by accessing pixels stored in a frame buffer in memory. The video controller uses two registers to iterate through each pixel location, retrieving the pixel value and using it to set the intensity of the CRT beam. It draws one scan line at a time from top to bottom until the entire screen is refreshed at a rate of 60 frames per second. Display processors can offload graphics processing tasks from the CPU by performing operations like scan conversion and generating lines and color areas to draw objects in the frame buffer.
This document provides information about different types of display devices used in computer graphics. It discusses cathode ray tube (CRT) displays, including how CRTs work using an electron gun and accelerating electrons to excite phosphors to emit light. It describes raster scan displays, which draw images as a grid of pixels by sweeping an electron beam across the screen, and random scan displays, which draw images line by line. The document also covers color CRT displays using beam penetration or a shadow mask to combine red, green, and blue phosphors at each pixel location.
presentation By Daroko blog-where IT learners Apply skills.
This topic an presentation will introduce you to Computer graphics hardware types.
---------------------------------
• Daroko blog (www.professionalbloggertricks.com)
• Presentation by Daroko blog, to see More tutorials more than this one here, Daroko blog has all tutorials related with IT course, simply visit the site by simply Entering the phrase Daroko blog (www.professionalbloggertricks.com) to search engines such as Google or yahoo!, learn some Blogging, affiliate marketing ,and ways of making Money with the computer graphic Applications(it is useless to learn all these tutorials when you can apply them as a student you know),also learn where you can apply all IT skills in a real Business Environment after learning Graphics another computer realate courses.ly
• Be practically real, not just academic reader
Do Not just learn computer graphics an close your computer tab and go away..
APPLY them in real business,
Visit Daroko blog for real IT skills applications,androind, Computer graphics,Networking,Programming,IT jobs Types, IT news and applications,blogging,Builing a website, IT companies and how you can form yours, Technology news and very many More IT related subject.
-simply google:Daroko blog(professionalbloggertricks.com)
Raster scan displays work by sweeping an electron beam across the screen one row at a time from top to bottom, turning the beam's intensity on and off to create illuminated spots. This allows the display to store an entire frame of picture data in a frame buffer memory. Raster scanning is well suited for realistic scenes like television and refreshes at 60-80 frames per second. Random scan displays direct the electron beam only where a picture element needs to be drawn, storing pictures as a set of line drawing commands rather than a frame buffer. It is better for applications like plotters that draw individual lines.
The document describes the components and operation of a raster scan graphics display system. A video controller accesses a frame buffer in system memory to refresh the screen. It performs operations like retrieving pixel intensities from different memory areas and using two frame buffers to allow refreshing one screen while filling the other for animation. A raster scan display processor can digitize graphics into pixel intensities for storage in the frame buffer to offload this processing from the CPU.
This document provides an overview of computer graphics hardware and software. It defines computer graphics as using a computer to define, store, manipulate, interrogate and present pictorial output. The key hardware components discussed are display devices like CRT, LCD, and plasma displays. Software components include rendering primitives, algorithms for transformation and rasterization, and application programming interfaces that provide access to graphics hardware. The graphics rendering pipeline is described as the process of converting a 3D scene model into a 2D image through steps like modeling transformations, viewing transformations, projection, clipping and rasterization.
This document summarizes different types of display devices, including cathode ray tubes (CRTs), raster scan displays, random scan displays, liquid crystal displays (LCDs), and light emitting diodes (LEDs). It describes the basic components and functioning of CRTs, including electron guns, phosphor coatings, and deflection coils. It compares raster and random scan displays, noting that raster displays are better for realistic images while random scans are suited for line drawings. LCDs use polarized light passing through liquid crystals to turn pixels on and off. LED displays use semiconductors to emit light when forward biased, and have advantages over traditional light sources like lower energy use and longer lifetimes.
Introduction to computer graphics part 1Ankit Garg
This document discusses computer graphics systems and their components. It describes video display devices like CRTs and how they work. Color is generated using techniques like beam penetration and shadow masks. Raster scan and random scan displays are covered. Input devices for graphics like mice, tablets, and gloves are also summarized. The document provides details on graphics hardware like frame buffers, refresh rates, and video controllers.
This document provides an overview of graphics display systems. It discusses the basic components and operation of cathode ray tube (CRT) displays, including the electron gun, focusing and deflection systems. It describes the refresh process of raster-scan CRTs and how random-scan CRTs work. Color CRT monitors are discussed, specifically the beam penetration and shadow mask methods. Key characteristics like resolution, persistence and aspect ratio are also summarized.
CG03 Random Raster Scan displays and Color CRTs.ppsxjyoti_lakhani
The document discusses different types of graphics displays. It describes raster-scan displays, which use an electron beam that sweeps across the screen from top to bottom to display an image. Picture definition is stored in a frame buffer. It also describes random-scan displays, which direct the electron beam only where lines need to be drawn. Color CRT monitors use phosphors and a shadow mask to display color. Flat panel displays like plasma panels, thin-film electroluminescent displays, and liquid crystal displays provide thinner alternatives to CRTs.
This PPT gives detailed information about Computer Graphics, Raster Scan System, Random Scan System, CRT Display, Color CRT Monitors, Input and Output Devices
The document provides an overview of computer graphics systems. It discusses different types of display devices including refresh cathode-ray tubes, raster-scan displays, random-scan displays, color CRT monitors, and flat panel displays. It also covers basics of raster graphics systems and random scan systems, including components like the video controller, display processor, and frame buffer. Input devices for graphics systems such as the keyboard, mouse, and digitizer are also mentioned.
This document discusses computer graphics systems and their components. It describes common display devices like CRT monitors and how they work. It explains color generation techniques in monitors using beam penetration or shadow mask methods. Input devices for graphics like mice, tablets, and joysticks are also covered. The document provides details on frame buffers, resolution, refresh rates and how raster scan displays redraw images.
This document provides information on different types of display devices and monitor technologies. It discusses cathode ray tube (CRT) displays, including their structure, working principle, and technologies such as raster scan and vector scan displays. Liquid crystal displays (LCD) and plasma displays are also mentioned. Key aspects of displays such as pixels, resolution, size, viewing angle, response time, and brightness are defined. CRTs are described as having advantages like high resolution and wide viewing angles, but also disadvantages like large thickness and weight.
Introduction to computer graphics part 2Ankit Garg
This document discusses cathode ray tubes (CRTs) and how they work as display devices for computer graphics. It explains that CRTs contain an electron gun that emits a stream of electrons which are focused into a beam and directed to specific points on the phosphor-coated front of the picture tube. When the electron beam hits a phosphor dot, it glows proportionally to the beam strength. Color CRTs use three electron guns and a shadow mask to separately excite red, green, and blue phosphor dots, allowing for color displays. The document also covers other properties of CRTs like resolution, persistence, and aspect ratio.
The document provides information on different types of display devices used in computer graphics, including CRT, color CRT monitors, direct view storage tubes, and flat panel displays. It describes the key components and working of CRTs, including the electron gun, phosphor coating, control grid, deflection plates, and techniques for color CRT monitors. Raster scan and random scan are introduced as techniques for producing images on CRT screens. Details are provided on components like shadow mask and refresh buffer used in raster scan systems.
This document discusses different types of displays including emissive displays like CRTs and LEDs, and non-emissive displays like LCDs. It focuses on describing the components and workings of CRT displays, including the electron gun, phosphor coating, and use of shadow masks for color displays. Key properties of CRTs discussed are phosphor persistence, refresh rate, resolution, and dot pitch. The document also compares vector and raster output scan technologies, and describes the components of a basic raster display system including the frame buffer, video controller, and color look-up table.
Computer graphics uses computers to draw and display pictures, graphics, and data in pictorial form. It expresses data visually instead of just text. Computer graphics is used in movies, games, medical imaging, design, education, simulators, art, presentations, image processing, and graphical user interfaces. Pixels are the smallest display elements on a screen, each with an intensity and color value. Interactive graphics allow user input to modify images, while passive graphics do not. Common display devices are CRT monitors which use electron beams to excite phosphors and LCD screens which use pixels to control light transmission. Algorithms like DDA and Bresenham's are used to draw lines on these displays.
Computer graphics involves rendering pictures, charts, and graphs on computers rather than just text. It has many applications including movies, games, medical imaging, CAD, education, and simulations. Computer graphics uses pixels - the smallest display elements - to represent images on screens. There are two main types: interactive graphics which allow user input, and passive graphics which do not. Raster scan displays refresh images by sweeping an electron beam across the screen in lines, while random scan displays draw images line by line. Algorithms like DDA and Bresenham's are used to efficiently render lines and circles of pixels.
The document discusses various display devices including CRT, flat panel displays, and their components and technologies. CRTs use an electron gun and phosphor-coated screen to create images and come in random scan and raster scan varieties. Components include the electron gun, control electrodes, focusing system, and deflection yoke. Flat panel displays are thinner than CRTs and include LCD and plasma displays.
The document discusses various display devices used for visual presentation of information. It describes cathode ray tubes (CRT), which use electron guns and phosphorescent coatings to produce images. Raster scan displays refresh images by sweeping an electron beam across the screen in rows, while random scan displays draw individual lines. Liquid crystal displays (LCD) use polarized light passing through liquid crystals. Light emitting diodes (LED) also emit light when electrically biased and are used in displays and lighting due to their low energy use and long lifetime. The document provides details on the components and functioning of CRTs and explains the differences between raster and random scan displays.
Cathode ray tubes (CRTs) were a common display technology that used electron beams to excite phosphors on the inside of an evacuated glass envelope. The electron beams were generated by electron guns and controlled by deflection plates and coils to scan across the phosphor-coated screen in a raster pattern, refreshing the image rapidly to prevent flickering. Different phosphors determined the persistence of the light emission and were used together with color masks and intensity control to generate color images on CRT displays. Random scan displays stored images as line drawings and refreshed all lines periodically rather than using a raster scan.
Raster scan displays work by sweeping an electron beam across the screen in horizontal lines from top to bottom. As the beam moves, its intensity is turned on and off to illuminate pixels and form an image. The pixel values are stored in and retrieved from a refresh buffer or frame buffer. Random scan displays draw images using geometric primitives like points and lines based on mathematical equations, directing the electron beam only where needed. Raster scans have higher resolution but jagged lines, while random scans produce smooth lines but cannot display complex images. Both use a video controller and frame buffer in memory to control the display process.
Random scan displays and raster scan displaysSomya Bagai
Raster scan displays work by sweeping an electron beam across the screen in horizontal lines from top to bottom. As the beam moves, its intensity is turned on and off to illuminate pixels and form an image. The pixel values are stored in and retrieved from a refresh buffer or frame buffer. Random scan displays draw images using geometric primitives like points and lines based on mathematical equations, directing the electron beam only where needed. Raster scans have higher resolution but jagged lines, while random scans produce smooth lines but cannot display complex images. Both use a video controller and frame buffer in memory to control the display process.
The document discusses different types of displays including emissive displays like CRTs and non-emissive displays like LCDs. It then provides details on how CRTs work including the electron gun, deflection coils, and phosphor screen. Key properties of CRTs are described such as resolution, refresh rate, and color reproduction using an electron gun and shadow mask arrangement. Raster scanning is introduced as the process of drawing the image line by line using a frame buffer and video controller. Color mapping with a lookup table is also summarized.
The document discusses different types of displays including emissive displays like CRTs and non-emissive displays like LCDs. It then provides details on how CRTs work including the electron gun, deflection coils, and phosphor screen. Key properties of CRTs are described such as resolution, refresh rate, and color reproduction using an electron gun and shadow mask arrangement. Raster scanning is introduced as the process of drawing the image line by line using a frame buffer and video controller. Color mapping with a lookup table is also summarized.
This document provides an overview of graphics systems including video display devices, input devices, and raster-scan systems. It describes cathode ray tube monitors as the primary output device and discusses raster-scan and random-scan display principles. Color CRT monitors use color phosphors and shadow masks or electron guns to produce color. Flat panel displays like plasma panels and LCDs are also covered. Common input devices include mice, keyboards, tablets, and touchscreens. Raster-scan systems use a frame buffer in video memory that is refreshed by a video controller to display an image on a monitor.
In a raster scan display, the screen is divided into a grid of pixels that are scanned line by line from top to bottom. Each pixel is either on or off, controlled by values stored in a frame buffer. The electron beam scans across each line from left to right, then returns to the left side to draw the next line, in a process called horizontal retrace. After completing the frame, the beam returns to the top left corner for the next frame during vertical retrace. Interlacing displays every other line to reduce flicker.
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 3)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
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1. CG
Chapter Two
Video Display Devices
Tips: Install MinGw on you Computer
Integrate freeglut with CodeBlocks(Optional)
Class on Tuesday 16, April @10:30AM-Venue VIII-1
5. OVERVIEW
The display systems are often referred to as Video Monitor or Video
display Unit(VDU).
The primary output device in a graphics system is a monitor.
5
6. CRT (CATHODE RAY TUBES)
1. Electron Guns
2. Electron Beams
3. Focusing Coils
4. Deflection Coils
5. Anode Connection
6. Shadow Mask
7. Phosphor layer
8. Close-up of the phosphor coated
inner side of the screen
6
9. …REFRESH CRT
Light 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.
Electron Gun: Heat is supplied to the cathode by the filament.
9
10. …ELECTRON GUN
The free electrons are then accelerated toward the phosphor coating by a high positive
voltage.
High Positive Voltage: a positively charged metal coating on the inside of the CRT
envelope near the phosphor screen.
1
0
11. … HIGH POSITIVE VOLTAGE
accelerating anode.
Intensity of the electron beam is controlled by setting voltage level on the
control grid.
smaller negative voltage on the control grid simply decrease the number of electrons
passing through. 1
1
12. …FOCUSING SYSTEM
The 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
With electrostatic focusing, the electron beam passes through a positively charged
metal cylinder that forms an electrostatic lens.
1
2
13. …FOCUSING SYSTEM
The 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.
The 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.
1
3
14. …DEFLECTION SYSTEMS
Deflection 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.
1
4
15. …DEFLECTION SYSTEMS
Two pairs of coils are used, with the coils in each pair mounted on opposite sides of
the neck of the CRT envelope.
One pair is mounted on the top and bottom of the neck, and the other pair is mounted
on opposite sides of the neck.
1
5
16. …DEFLECTION SYSTEMS
Horizontal 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.
Electrostatic deflection: Two pairs of parallel plates are mounted inside the CRT
envelope.
One pair of plates is mounted horizontally to control the vertical deflection, and the
other pair is mounted vertically to control horizontal deflection.
1
6
18. …RASTER SCAN DISPLAYS
Raster: A rectangular array of points or dots
Pixel: One dot or picture element of the raster
Scan Line: A row of pixels
In a raster scan system, the electron beam is swept across the screen, one row at a time
from top to bottom
1
8
20. …RASTER SCAN DISPLAYS
As the electron beam moves across each row, the beam intensity is turned on and off
to create a pattern of illuminated spots.
Picture definition is stored in a memory area called the refresh buffer or frame buffer.
2
0
21. …RASTER SCAN DISPLAYS
Refresh buffer or frame buffer: This memory area holds the set of intensity values for
all the screen points.
Stored intensity values then retrieved from refresh buffer and “painted” on the screen
one row (scan line) at a time.
2
1
22. …RASTER SCAN DISPLAYS
Intensity 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.
On 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
Sometimes, refresh rates are described in unit of cycles per second, or Hertz (HZ)
Refreshing on raster scan displays is carried out at the rate 60 to 80 frame per second
2
2
23. …RASTER SCAN DISPLAYS
Horizontal retrace: The return to the left of the screen, after refreshing each scan line
Vertical 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
23
24. …RASTER IMAGE
The quality of a raster image is determined by the total number pixels (resolution), and
the amount of information in each pixel (color depth).
Raster graphics cannot be scaled to a higher resolution without loss of apparent
quality.
24
25. Random scan Display
CRT has the electron beam directed only to the parts of the screen where a picture
is to be drawn.
are also referred to as vector displays (or stroke-writing or calligraphic displays)
because Random scan monitors draw a picture one line at a time
A pen plotter operates in a similar way and is an example of a random-scan, hard-copy
device.
Refresh rate depends on the number of lines to be displayed.
Picture definition is stored as a set of line drawing commands in an area of memory
referred to as the refresh display file/display list.
25
26. Random scan Display
The refresh display file is called the display list, display program, or simply the
refresh buffer.
To display a specified picture, the system cycles through the set of commands in the
display file, drawing each component line in turn.
Random-scan systems are designed for line drawing applications and cannot display
realistic shaded scenes.
vector displays generally have higher resolution than raster systems.
26
27. Random scan Display (Cont’d)
A random-scan system draws the component lines of an object in any order specified
27
28. Exercise(get a Reward)
1. Discuss the difference between Raster scan Random Scan?
2. What is the difference between Vertical and Horizontal retrace?
28
29. Raster Scan Vs Random scan Display
.
29
Base of Difference Raster Scan System Random Scan System
Electron Beam The electron beam is swept across the
screen, one row at a time, from top to
bottom.
The electron beam is directed only to the parts of
screen where a picture is to be drawn.
Resolution Its resolution is poor because raster system
in contrast produces zigzag lines that are
plotted as discrete point sets.
Its resolution is good because this system
produces smooth lines drawings because CRT
beam directly follows the line path.
Picture Definition Picture definition is stored as a set of
intensity values for all screen points, called
pixels in a refresh buffer area.
Picture definition is stored as a set of line
drawing instructions in a display file.
Realistic Display The capability of this system to store
intensity values for pixel makes it well
suited for the realistic display of scenes
contain shadow and color pattern.
These systems are designed for line drawing and
can’t display realistic shaded scenes.
Draw an Image Screen points/pixels are used to draw an
image
Mathematical functions are used to draw an
image
30. Color CRT Monitors
A CRT monitor displays color pictures by using a combination of phosphors that emit
different-colored light.
Two basic technique is applied to produce color display:
Beam-penetration method:
•used with random-scan monitors
•usually red and green, are coated onto the inside of the CRT screen, and the
displayed color depends on how far the electron beam penetrates into the
phosphor layers.
• A beam of slow electrons excites only the outer red layer.
30
31. Color CRT Monitors
Beam-penetration method:
•A beam of very fast electrons penetrates through the red layer and excites the
inner green layer.
•At intermediate beam speeds, combinations of red and green light are emitted to
show two additional colors, orange and yellow.
•The speed of the electrons, and hence the screen color at any point, is controlled
by the beam-acceleration voltage.
•Beam penetration has been an inexpensive way to produce color in random-scan
monitors, but only four colors are possible, and the quality of pictures is not as
good as with other methods.
31
33. Color CRT Monitors(Cont’d)
Shadow-Mask Method:
Commonly used in raster-scan systems (including color TV) because they produce
a much wider range of colors than the beam-penetration method.
has three phosphor color dots at each pixel position.
One phosphor dot emits a red light, another emits a green light, and the third emits
a blue light.
This type of CRT has three electron guns, one for each color dot, and a shadow-
mask grid just behind the phosphor-coated screen.
The three electron beams are deflected and focused as a group onto the shadow
mask, which contains a series of holes aligned with the phosphor-dot patterns.
33
34. Color CRT Monitors(Cont’d)
…Shadow-Mask Method:
When the three beams pass through a hole in the shadow mask, they activate a dot
triangle, which appears as a small color spot on the screen.
The phosphor dots in the triangles are arranged so that each electron beam can
activate only its corresponding color dot when it passes through the shadow mask.
Another configuration for the three electron guns is an in-line arrangement in
which the three electron guns, and the corresponding red-green-blue color dots
on the screen, are aligned along one scan line instead of in a triangular pattern.
This in-line arrangement of electron guns is easier to keep in alignment and is
commonly used in high-resolution color CRTs.
34
36. Color CRT Monitors(Cont’d)
.
Three electron guns, aligned with the triangular color-dot patterns on the screen, are directed to each
dot triangle by a shadow mask.
36
38. Color CRT Monitors(Cont’d)
Shadow-Mask Method:
We obtain color variations in a shadow-mask CRT by varying the intensity levels of
the three electron beams.
By turning off the red and green guns, we get only the color coming from the blue
phosphor.
Other combinations of beam intensities produce a small light spot for each pixel
position, since our eyes tend to merge the three colors into one composite.
The color we see depends on the amount of excitation of the red, green, and blue
phosphors.
A white (or gray) area is the result of activating all three dots with equal intensity.
38
39. Color CRT Monitors(Cont’d)
Shadow-Mask Method:
Yellow is produced with the green and red dots only, magenta is produced with the
blue and red dots, and cyan shows up when blue and green are activated equally
Color CRTs in graphics systems are designed as RGB monitors.
These monitors use shadow-mask methods and take the intensity level for each
electron gun (red, green, and blue) directly from the computer system without any
intermediate processing.
High-quality raster-graphics systems have 24 bits per pixel in the frame buffer,
allowing 256 voltage settings for each electron gun and nearly 17 million color choices
for each pixel.
39
40. Color CRT Monitors(Cont’d)
An RGB color system with 24 bits of storage per pixel is generally referred to as a
full-color system or a true-color system.
Direct-View Storage Tubes :
An alternative method for maintaining a screen image is to store the picture
information inside the CRT instead of refreshing the screen.
A direct-view storage tube (DVST) stores the picture information as a charge
distribution just behind the phosphor-coated screen.
Two electron guns are used in a DVST.
the primary gun, is used to store the picture pattern;
the flood gun, maintains the picture display. 40
41. Color CRT Monitors(Cont’d)
advantages compared to the refresh CRT: Because no refreshing is needed, very
complex pictures can be displayed at very high resolutions without flicker.
Disadvantages: they ordinarily do not display color and that selected parts of a picture
cannot he erased. To eliminate a picture section, the entire screen must be erased and the
modified picture is redrawn.
The erasing and redrawing process can take several seconds for a complex picture.
For these reasons, storage displays have been largely replaced by raster systems
41
42. Color Models
R, G, and B represent the colors produced by red, green and blue phosphors, respectively.
42
45. Color Depth, Bit Depth
The 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.
A minimum of one memory bit (color depth=1) is required to store intensity value either
0 or1 for every screen pixel.
If there are n pixels in an image a total of n bits memory is used for storing intensity
values (in a pure black & white image)
45
46. Bit Plane
The block of memory which stores (or is mapped with) intensity values for each pixel (B& W image) is
called a bit plane or bitmap.
46
47. 3Bit color display
Color or gray levels can be achieved in the display using additional bit planes.
47
48. True Color
For 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) .
48
49. Flat-Panel Displays
The term flat-panel display refers to a class of video devices that have reduced
volume, weight, and power requirements compared to a CRT.
A significant feature of flat-panel displays is that they are thinner than CRTs, and we
can hang them on walls or wear them on our wrists.
Since we can even write on some flat-panel displays, they will soon be available as
pocket notepads.
Current uses for flat-panel displays include small TV monitors, calculators, pocket
video games, laptop computers, armrest viewing of movies on airlines, as advertisement
boards in elevators, and as graphics displays in applications requiring rugged, portable
monitors.
49
50. Flat-Panel Displays
Two categories of flat-panel:
emissive displays : displays (or emitters) are devices that convert electrical
energy into light. Plasma panels, thin-film electroluminescent displays, and Light-
emitting diodes are examples of emissive displays.
Non-emissive displays: use optical effects to convert sunlight or light from some
other source into graphics patterns.
The most important example of a non-emissive flat-panel display is a liquid-
crystal device.
50
51. Three-Dimensional Viewing Devices
Graphics monitors for the display of three-dimensional scenes have been devised using a technique that
reflects a CRT image from a vibrating, flexible mirror.
51
52. Three-Dimensional Viewing Devices
From figure above, as the varifocal mirror vibrates, it changes focal length.
These vibrations are synchronized with the display of an object on a CRT so that each
point on the object is reflected from the mirror into a spatial position corresponding to
the distance of that point from a specified viewing position.
This allows us to walk around an object or scene and view it from different sides..
52
53. Pixel Resolution and Aspect Ratio
Resolution is technically the number of pixels per unit of area, rather than the total number of
pixels.
Pixel resolution refers to the total number of count of pixels in an digital image. For example, if
an image has M rows and N columns, then its resolution can be defined as M X N.
Pixel resolution can be defined with set of two numbers:- the first number the width of the
picture, or the pixels across columns, and the second number is height of the picture, or the pixels
across its width.
We can say that the higher is the pixel resolution, the higher is the quality of the image
Resolution can affected by: the type of phosphor, the intensity to be displayed, the focusing and
deflection systems.
53
54. Pixel Resolution and Aspect Ratio(Cont’d)
Aspect ratio is the ratio between width of an image and the height of an image.
It is commonly explained as two numbers separated by a colon (8:9).
This ratio differs in different images, and in different screens.
Example: If you are given an image with aspect ratio of 6:2 of an image of pixel resolution of
480000 pixels given the image is a gray scale image. Then calculate two things.
Resolve pixel resolution to calculate the dimensions of image
Calculate the size of the image
Aspect ratio: c:r = 6:2
Pixel resolution: c * r = 480000
Bits per pixel: grayscale image = 8
54
55. Pixel Resolution and Aspect Ratio(Cont’d)
Number of columns = ?
𝑐 𝑥 𝑟 = 480000
𝑐
𝑟
=
6
2
⇒ 𝑐2 = 480,000𝑥 3 ⇒ 𝑐 = 1200
Number of cols = ? 1200 * 𝑟 = 480,000 ⇒ 𝑟 = 400
Size = rows * cols * bpp
Size of image in bits = 400 * 1200 * 8 = 3840000 bits
Size of image in bytes = 480000 bytes
Size of image in kilo bytes = 48 kb (approximate).
What if the image is colored image?
55
56. Pixel Resolution and Aspect Ratio(Cont’d)
Consider two raster systems with the resolutions of 640x480, 1280x1024, and 2560x2048.
a) What size frame buffer (in bytes) is needed for each of these systems to store 12 bits/pixel? How much
storage is required for each system if true color image is to be stored?
56
57. Pixel Resolution and Aspect Ratio(Cont’d)
P's, and I's about screen resolutions
You may have seen the screen resolution described as something like 720p or 1080i.
What does that mean?
The letters tell you how the picture is "painted" on the monitor
A "p" stands for progressive, and an "i" stands for interlaced.
The interlaced scan is a holdover from television and early CRT monitors.
The monitor or TV screen has lines of pixels arranged horizontally across it.
The lines were relatively easy to see if you got up close to an older monitor or TV.
57
58. Pixel Resolution and Aspect Ratio(Cont’d)
P's, and I's about screen resolutions(Cont’d)
but nowadays the pixels on the screen are so small that they are hard to see even with
magnification.
The monitor's electronics "paint" each screen line by line, too quickly for the eye to
see.
An interlaced display paints all the odd lines first, then all the even lines.
58
59. RASTER-SCAN SYSTEMS
Interactive raster graphics systems typically employ several processing units.
In addition to the central processing unit, or CPU, a special-purpose processor, called
the video controller or display controller, is used to control the operation of the display
device.
The frame buffer can be anywhere in the system memory, and the video controller
accesses the frame buffer to refresh the screen.
In addition to the video controller, more sophisticated raster systems employ other
processors as co-processors and accelerators to implement various graphics operations.
59
61. …RASTER-SCAN SYSTEMS
Video Controller:
A 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.
Frame-buffer locations, and the corresponding screen positions, are referenced in
Cartesian coordinates.
For many graphics monitors, the coordinate origin is defined at the lower left screen
comer (see fig on next page).
The screen surface is then represented as the first quadrant of a two-dimensional
system, with positive x values increasing to the right and positive y values increasing
from bottom to top.
61
62. On some personal computers, the coordinate origin is referenced at the upper left
comer of the screen, so the y values are inverted.) Scan lines are then labeled
from 𝒚 𝒎𝒂𝒙 , at the top of the screen to 0 at the bottom. Along each scan line, screen
pixel positions are labeled from 0 to 𝑿 𝒎𝒂𝒙 .
[The origin of the coordinate system for identifying screen
positions is usually specified in the lower-left corner]
…RASTER-SCAN SYSTEMS
62
63. The basic refresh operations of the video controller are diagrammed on the next slide.
Two registers are used to store the coordinates of the screen pixels.
Initially, the x register is set to 0 and the y register is set to 𝒚 𝒎𝒂𝒙 .
The value stored in the frame buffer for this pixel position is then retrieved and used to set the intensity of
the CRT beam.
Then the x register is incremented by 1, and the process repeated for the next pixel on the top scan line.
This procedure is repeated for each pixel along the scan line.
After the last pixel on the top scan line has been processed, the x register is reset to 0 and the y register
is decremented by 1.
Pixels along this scan line are then processed in turn, and the procedure is repeated for each successive
scan line.
After cycling through all pixels along the bottom scan line (y = 0), the video controller resets the registers
to the first pixel position on the top scan line and the refresh process starts over.
…RASTER-SCAN SYSTEMS
63
64. Since the screen must be refreshed at the rate of 60 frames per second, the simple
procedure depicted in the figure on the next page cannot be accommodated by typical
RAM chips.
The cycle time is too slow.
To speed up pixel processing, video controllers can retrieve multiple pixel values from
the refresh buffer on each pass.
The multiple pixel intensities are then stored in a separate register and used to control
the CRT beam intensity for a group of adjacent pixels.
When that group of pixels has been processed, the next block of pixel values is
retrieved from the frame buffer.
…RASTER-SCAN SYSTEMS
64
67. Raster-Scan Display Processor(Cont’d):
The purpose of the display processor is to free the CPU from the graphics chores. In addition to the
system memory, a separate display processor memory area can also be provided.
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.
Graphics commands specifying straight lines and other geometric objects are scan converted into a set
of discrete intensity points.
Scan converting a straight-line segment, for example, means that we have to locate the pixel positions
closest to the line path and store the intensity for each position in the frame buffer.
Similar methods are used for scan converting curved lines and polygon outline.
…RASTER-SCAN SYSTEMS
67
68. Raster-Scan Display Processor(Cont’d):
[A character defined as a [A character defined as a curve outline]
rectangular grid of pixel
positions]
Additional functions of Display processor include generating various line styles (dashed, dotted, or
solid), displaying color areas, and performing certain transformations and manipulations on displayed
objects.
Also, display processors are typically designed to interface with interactive input devices, such as a
mouse.
…RASTER-SCAN SYSTEMS
68
69. An application program is input and stored in the system memory along with a graphics package
Graphics commands in the application program are translated by the graphics package into a display
file stored in the system memory.
RANDOM-SCAN SYSTEMS
69
70. A graphics package is an application that can be used to create and manipulate images
on a computer.
There are two main types of graphics package:
painting packages
A painting package produces images by changing the color of pixels on the screen.
These are coded as a pattern of bits to create a bitmapped graphics file.
Bitmapped graphics are used for images such as scanned photographs or pictures taken with a
digital camera.
drawing packages
Graphics Packages
70
71. This display file is then accessed by the display processor to refresh the screen.
The display processor cycles through each command in the display file program once during every
refresh cycle.
Sometimes the display processor in a random-scan system is referred to as a display processing
unit or a graphics controller.
Graphics patterns are drawn on a random-scan system by directing the electron beam along the
component lines of the picture.
Lines are defined by the values for their coordinate endpoints, and these input coordinate values are
converted to x and y deflection voltages.
A scene is then drawn one line at a time by positioning the beam to fill in the line between specified
endpoints.
…Random-scan Systems
71
73. Introduction
Points and Lines
Line Drawing Algorithms
DDA algorithm
Bresenham Line Drawing Algorithm
Parallel Line Algorithms
Loading The Frame Buffer
Circle Generating Algorithms
Ellipse Generating Algorithms
Chapter Outlines
73
74. In a raster display, a picture is completely specified by the set of intensities for the
pixel positions in the display.
Graphics programming packages provide functions to describe a scene in terms of these basic
geometric structures, referred to as output primitives, and to group sets of output primitives into more
complex structures.
Each output primitive is specified with input coordinate data and other information about the way that
object is to be displayed.
Points and straight line segments are the simplest geometric components of pictures.
Additional output primitives that can be used to construct a picture include circles and other conic
sections, quadric surfaces, spline curves and surfaces, polygon color areas, and character strings.
Introduction
74
75. Point plotting is accomplished by converting a single coordinate position furnished by an application
program into appropriate operations for the output de-vice in use.
With a CRT monitor, for example, the electron beam is turned on to illuminate the screen phosphor at
the selected location.
How the electron beam is positioned depends on the display technology.
A random-scan (vector) system stores point-plotting instructions in the display list, and coordinate
values in these instructions are converted to deflection voltages that position the electron beam at the
screen locations to be plotted during each refresh cycle.
For a black and white raster system, on the other hand, a point is plotted by setting the bit value
corresponding to a specified screen position within the frame buffer to 1. Then, as the electron beam
sweeps across each horizontal scan line, it emits a burst of electrons (plots a point) whenever a value
of 1(one) is encountered in the frame buffer.
With an RGB system, the frame buffer is loaded with the color codes for the intensities that are to be
displayed at the screen pixel positions.
Points and Lines
75
76. Line drawing is accomplished by calculating intermediate positions along the line path between two
specified endpoint positions.
An output device is then directed to fill in these positions between the endpoints.
For analog devices, such as a vector pen plotter or a random-scan display, a straight line can be
drawn smoothly from one endpoint to the other.
Linearly varying horizontal and vertical deflection voltages are generated that are proportional to
the required changes in the x and y directions to produce the smooth line.
Digital devices display a straight line segment by plotting discrete points between the two endpoints.
Discrete coordinate positions along the line path are calculated from the equation of the line.
For a raster video display, the line color (intensity) is then loaded into the frame buffer at the
corresponding pixel coordinates.
Reading from the frame buffer, the video controller then "plots" the screen pixels.
…Points and Lines(Cont’d)
76
77. Screen locations are referenced with integer values, so plotted positions may only approximate actual
Line positions between two specified endpoints.
A computed line position of (10.48,20.51), for example, would be converted to pixel position (10,21).
Thus rounding of coordinate values to integers causes lines to be displayed with a stair step appearance
("the jaggies"), as represented in the figure on the next page.
The characteristic stair step shape of raster lines is particularly noticeable on systems with low
resolution, and we can improve their appearance somewhat by displaying them on high-resolution
systems.
More effective techniques for smoothing raster lines are based on adjusting pixel intensities along
the line paths.
For the raster-graphics device-level algorithm, object positions are specified directly in integer device
coordinates.
Pixel positions are referenced according to scan-line number and column number (pixel position
across a scan line).
…Points and Lines(Cont’d)
77
78. Scan lines are numbered consecutively from 0, starting at the bottom of the screen; and pixel columns are
numbered from 0, left to right across each scan line.
fig 2.1 a fig 2.1 b
[Pie1 positions referenced by scan-
line number and column number.]
…Points and Lines(Cont’d)
78
79. The Cartesian slope-intercept equation for a straight line is:
𝑦 = 𝑚𝑥 + 𝑏 (2.1)
with mrepresenting the slope of the line and b as they intercept. Given that the two endpoints of a he
segment are specified at positions (x,, y,) and (x, y), as shown the following figure, we can determine
values for the slope mand y intercept b with the following calculations.
𝑚 =
𝑦2 − 𝑦1
𝑥2 − 𝑥1
(2.2)
𝑏 = 𝑦1 − 𝑚𝑥 (2.3)
[fig 2.2 Line path between endpoint positions (𝑥1, 𝑦1) and (𝑥2,𝑦2]
Line-Drawing Algorithms
79
80. For any given x interval 𝜟𝒙along a line, we can compute the corresponding y interval 𝜟𝒚from
equation 2.2 and 2.3 above.
Δ𝑦 = 𝑚Δ𝑥 (2.4)
Δ𝑥 =
Δ𝑦
𝑚
(2.5)
These equations form the basis for determining deflection voltages in analog devices.
For lines with slope magnitudes |m|< 1, Δ𝑥can be set proportional to a small horizontal deflection voltage and the
corresponding vertical deflection is then set proportional to Δ𝑦 as calculated from Eq. 2-4.
For lines whose slopes have magnitudes |m|< 1, 𝛥𝑦can be set proportional to a small vertical deflection voltage with the
corresponding horizontal deflection voltage set proportional to Δ𝑥, calculated from Eq. 2-5.
For lines with m = 1, 𝜟𝒙= 𝜟𝒚and the horizontal and vertical deflections voltages are equal.
In each case, a smooth line with slope m is generated between the specified endpoints.
…Line-Drawing Algorithms(Cont’d)
80
81. On raster systems, lines are plotted with pixels, and step sizes in the horizontal and vertical directions
are constrained by pixel separations.
That is, we must "sample" a line at discrete positions and determine the nearest pixel to the line at each
sampled position. This scan conversion process for straight lines is illustrated below.
[Straight line segment with five sampling positions along
the x axis between 𝑥1 and 𝑥2]
Fig 2.3
…Line-Drawing Algorithms(Cont’d)
81
82. DDA Algorithm: The digital differential analyzer (DDA) is a scan-conversion line algorithm based on
calculating either 𝜟y or 𝜟𝒙, using Eq. 2-4 or Eq. 2-5.
We sample the line at unit intervals in one coordinate and determine corresponding integer values
nearest to the line path for the other coordinate.
Consider first a line with positive slope, as shown below. If the slope is less than or equal to 1, we sample
at unit x intervals (𝜟𝒙 = 1) and compute each successive y value as:
𝑦 𝑘+1 = 𝑦 𝑘 + 𝑚 2.6
fig 2.4
Subscript k takes integer values starting from 1, for the first point, and increases by 1 until the final endpoint is
reached. Since mcan be any real number between 0 and 1, the calculated y values must be rounded to the nearest
integer.
…Line-Drawing Algorithms(Cont’d)
82
83. …DDA Algorithm:
For lines with a positive slope greater than 1, we reverse the roles of x and y. That is, we sample at unit y
intervals (𝜟y = 1) and calculate each succeeding x value as:
𝑥 𝑘+1 = 𝑥 𝑘 +
1
𝑚
2.7
Equations 2.6 and 2.7 are based on the assumption that lines are to be processed from the left endpoint to
the right endpoint. If this processing is reversed, so that the starting endpoint is at the right, then either we
have 𝜟𝒙= -1 and
𝑦 𝑘+1 = 𝑦 𝑘 − 𝑚 2.8
or (when the slope is greater than I) we have 𝜟y = -1 with
𝑋 𝑘+1 = 𝑥 𝑘 −
1
𝑚
2.9
…Line-Drawing Algorithms(Cont’d)
83
84. …DDA Algorithm:
Equations 2.6 through 2.9 can also be used to calculate pixel positions along a line with negative slope. If
the absolute value of the slope is less than 1 and the start endpoint is at the left, we set 𝜟𝒙 = 1 and
calculate y values with Eq. 2.6.
When the start endpoint is at the right (for the same slope), we set 𝜟𝒙= -1 and obtain y positions from Eq.
2.8.
Similarly, when the absolute value of a negative slope is greater than 1, we use 𝜟y = -1and Eq. 2.9 or we
use 𝜟𝒚 = 1 and Eq. 2.7.
Advantages of DDA Algorithm over the equation: 𝑦 = 𝑚𝑥 + 𝑏 :
faster method for calculating pixel positions than the direct use of 𝑦 = 𝑚𝑥 + 𝑏.
Eliminates the multiplicationby making use of raster characteristics, so that appropriate increments are
applied in the x or y direction to step to pixel positions along the line path.
…Line-Drawing Algorithms(Cont’d)
84
85. …Disadvantages of DDA Algorithm :
The accumulation of roundoff error in successive additions of the floating-point increment, however, can
cause the calculated pixel positions to drift away from the true line path for long line segments.
Furthermore, the rounding operations and floating-point arithmetic in procedure lineDDA are still time-
consuming.
We can improve the performance of the DDA algorithm by separating the increments m and l/m into
integer and fractional parts so that all calculation are reduced to integer operations.
…Line-Drawing Algorithms(Cont’d)
85
86. Bresenham's Line Algorithm:
An accurate and efficient raster line-generating algorithm, developed by Bresenham, scan converts lines
using only incrementa1 integer calculations that can be adapted to display circles and other curves.
Fig 2.5 a fig 2.5 b
[Section of a display screen where a straight line segment [Section of a display screen where a negative slope line
1s to be plotted, starting from the pixel at column 10 on scan segment 1s to be plotted starting from the pixel at
Line 11 ] column 50 on scan line 50]
…Line-Drawing Algorithms(Cont’d)
86
87. Bresenham's Line Algorithm:
…Figures 2.5(a) and 2.5(b) above illustrate sections of a display screen where straight line segments are
to be drawn.
The vertical axes show scan-line positions, and the horizontal axes identify pixel columns.
Sampling at unit x intervals in these examples, we need to decide which of two possible pixel positions is
closer to the line path at each sample step.
Starting from the left endpoint shown in Fig. 2.5(a), we need to determine at the next sample position
whether to plot the pixel at position (11, 11) or the one at (11, 12).
Similarly, Fig. 2.5(b) shows-a negative slope-line path starting from the left endpoint at pixel position
(50, 50). In this one, do we select the next pixel position as (51,50) or as (51,49)?
These questions are answered with Bresenham's line algorithm by testing the sign of an integer parameter,
whose value is proportional to the difference between the separations of the two pixel positions from the
actual line path.
…Line-Drawing Algorithms(Cont’d)
87
88. Bresenham's Line Algorithm:
…To illustrate Bresenham's approach, we first consider the scan-conversion process for lines with positive
slope less than 1.
Pixel positions along a line path are then determined by sampling at unit x intervals.
Starting from the left endpoint (𝑥0, 𝑦0) of a given line, we step to each successive column (x position) and plot
the pixel whose scan-line y value is closest to the line path.
[Fig 2.6Section of the screen grid showing a pixel in column 𝒙 𝒌on scan line 𝒙 𝒌 that is to be plotted along the path of a
line segment with slope O<m<l. ]
…Line-Drawing Algorithms(Cont’d)
88
89. Bresenham's Line Algorithm:
…Figure 2.6 above demonstrates the 𝒌𝐭𝐡 step in this process. Assuming we have determined that the
pixel at (𝒙 𝒌, 𝒚 𝒌) is to be displayed, we next need to decide which pixel to plot in column𝒙 𝒌+𝟏.
Our choices are the pixels at positions (𝒙 𝒌+𝟏, 𝒚 𝒌) and ((𝒙 𝒌+𝟏, 𝒚 𝒌+𝟏).
At sampling position 𝒙 𝒌+𝟏, we label vertical pixel separations from the mathematical line path as 𝒅 𝟏and
𝒅 𝟐. See the following figure.
fig 2.7
[Distances between pixel positions and the line y
coordinate at sampling position xk+1]
…Line-Drawing Algorithms(Cont’d)
89
90. Bresenham's Line Algorithm:
…They coordinate on the mathematical line at pixel column position 𝒙 𝒌+𝟏 is calculated as:
𝒚 = 𝒎 𝒙 𝒌 + 𝟏 + 𝒃2.10
Then
𝑑1 = 𝑦 − 𝑦 𝑘
= 𝑚 𝑥 𝑘 + 1 + 𝑏 − 𝑦 𝑘
And
𝑑2 = 𝑦 𝑘 + 1 − 𝑦
= 𝑦 𝑘 + 1 − 𝑚 𝑥 𝑘 + 1 − 𝑏
The difference between these two separations is
𝑑1 − 𝑑2 = 2𝑚 𝑥 𝑘 + 1 − 2𝑦 𝑘 + 2𝑏 − 1 2.11
…Line-Drawing Algorithms(Cont’d)
90
91. Bresenham's Line Algorithm:
…A decision parameter 𝒑 𝒌 for the kth step in the line algorithm can be obtained by rearranging Eq. 2.11
so that it involves only integer calculations. We accomplish this by substituting m =
𝜟𝒚
𝜟𝒙
, where 𝜟𝒚 and
𝜟𝒙are the vertical and horizontal separations of the endpoint positions, and defining:
𝑝 𝑘 = Δ𝑥 𝑑1 − 𝑑2
= 2Δ𝑦. 𝑥 𝑘 − 2Δ𝑥. 𝑦 𝑘 +𝑐 2.12
The sign of 𝒑 𝒌 , is the same as the sign of 𝒅 𝟏 − 𝒅 𝟐since 𝚫𝒙> 0 for our example.
Parameter c is constant and has the value 2Δ𝑦 + 𝚫𝒙(2b - l), which is independent of pixel position and will be
eliminated in the recursive calculations for 𝒑 𝒌.
If the pixel at 𝒚 𝒌 is closer to the line path than the pixel at 𝑦 𝑘+ l (that is, 𝒅 𝟏<𝒅 𝟐), then decision parameter
𝒑 𝒌 is negative.
In that case, we plot the lower pixel; otherwise, we plot the upper pixel.
…Line-Drawing Algorithms(Cont’d)
91
92. Bresenham's Line Algorithm:
…Coordinate changes along the line occur in unit steps in either the x or y directions.
Therefore, we can obtain the values of successive decision parameters using incremental integer
calculations.
At step k + 1, the decision parameter is evaluated from Eq. 2.12 as
𝑝 𝑘+1 = 2Δ𝑦. 𝑥 𝑘+1 −2Δ𝑥. 𝑦 𝑘+1 +𝑐
Subtracting Eq. 2.12 from the preceding equation, we have
𝑝 𝑘+1− 𝑝 𝑘 = 2Δ𝑦(𝑥 𝑘+1 − 𝑥 𝑘) −2Δ𝑥(𝑦 𝑘+1 − 𝑦 𝑘) but 𝑥 𝑘+1 = 𝑥 𝑘 +1, therefore,
𝑝 𝑘+1 = 𝑝 𝑘 + 2Δ𝑦 − 2Δ𝑥 (𝑦 𝑘+1 − 𝑦 𝑘) 2.13
where the term 𝒚 𝒌+𝟏 − 𝒚 𝒌 is either 0 or 1, depending on the sign of parameter 𝑝 𝑘. This recursive
calculation of decision parameters is performed at each integer x position, starting at the left coordinate
endpoint of the line.
The first parameter, 𝑝0 is evaluated from Eq. 2.12 at the starting pixel position (𝒙 𝟎, 𝒚 𝟎) and with m
evaluated as Δ𝑦/Δ𝑥: 𝑝0 = 2Δ𝑦 − Δ𝑥 2.14
…Line-Drawing Algorithms(Cont’d)
92
93. Bresenham's Line Algorithm:
…We can summarize Bresenham line drawing for a line with a positive slope less than 1 in the following listed
steps. The constants 𝟐𝚫𝒚and 𝟐𝜟𝒚 - 𝟐𝜟𝒙 are calculated once for each line to be scan converted, so the arithmetic
involves only integer addition and subtraction of these two constants.
Algorithm: 1. Input the two line endpoints and store the left endpoint in (𝒙 𝟎, 𝒚 𝟎)
2. Load (𝒙 𝟎, 𝒚 𝟎) into the frame buffer; that is, plot the first point
3. Calculate constants 𝜟𝒙, 𝜟𝒚, 𝟐𝜟𝒚, and 𝟐𝜟𝒚 − 𝟐𝜟𝒙, and obtain the starting value for the decision
parameter as: 𝑝0 = 2Δ𝑦 − Δ𝑥
4. At each 𝒙 𝒌 along the line, starting at k = 0, perform the following test:
If 𝑝 𝑘< 0, the next point to plot is (𝒙 𝒌 +1, 𝒚 𝒌) and
𝑝 𝑘+1 = 𝑝 𝑘 + 2Δ𝑦
Otherwise, the next point to plot is (𝒙 𝒌 +1, 𝒚 𝒌+ 1) and
𝑝 𝑘+1 = 𝑝 𝑘 + 2Δ𝑦 − 𝟐𝜟𝒙
5. repeat step 4 𝜟𝒙 times
…Line-Drawing Algorithms(Cont’d)
93
94. Bresenham's Line Algorithm:
Example: To illustrate the algorithm, we digitize the line with endpoints (20, 10) and (30, 18). This line has a slope
of 0.8, with 𝚫𝒙= 10, 𝚫𝐲 = 𝟖, The initial decision parameter has the value 𝑝0 = 2Δ𝑦 − Δ𝑥 = 6 and the increments for
calculating successive decision parameters are 𝟐𝚫𝒚 = 16, 𝟐𝚫𝒚 − 𝟐𝜟𝒙 = −𝟒.
We plot the initial point (𝒙 𝟎, 𝒚 𝟎) = (20, l0), and determine successive pixel positions along the line path from the
decision parameter as
…Line-Drawing Algorithms(Cont’d)
94
k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1) k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1)
0 6 (21,11) 5 6 (26,15)
1 2 (22,12) 6 2 (27,16)
2 -2 (23,12) 7 -2 (28,16)
3 14 (24,13) 8 14 (29,17)
4 10 (25,14) 9 10 (30,18)
95. Since the circle is a frequently used component in pictures and graphs, a procedure for generating either
full circles or circular arcs is included in most graphics packages.
A circle is defined as the set of points that are all at a given distance r from a center position (𝒙 𝟎, 𝒚 𝟎). This distance
relationship is expressed by the Pythagorean theorem in Cartesian coordinates as:
𝑥 − 𝑥c
2 + 𝑦 − 𝑦c
2 = 𝑟2 2.24
Fig 3.8
[circle with center coordinate (𝑥c,𝑦c) and radius r.
…Circle-Generating Algorithms
95
96. We could use this equation to calculate the position of points on a circle circumference by stepping along the x
axis in unit steps from xc - r to xc+ r and calculating the corresponding y values at each position as
𝑦 = 𝑦𝑐 ± 𝑟2 − 𝑥 𝑐 − 𝑥 2 2.25
but this not the best method for generating a circle.
it involves considerable computation at each step.
spacing between plotted pixel positions is not uniform
Fig 3.9
[Positive half of a circle plotted with Eq. 2.25 and with (𝑥 𝑐, 𝑦𝑐 = (0.0)]
…Circle-Generating Algorithms (Cont’d)
96
97. To eliminate the unequal spacing shown in Fig. 3.9 above is to calculate points along the circular boundary using
polar coordinates r and 𝜃(Fig. 3.8). Expressing the circle equation in parametric polar form yields the pair of
equations.
𝑥 = 𝑥 𝑐 + 𝑟 cos 𝜃
𝑦 = 𝑦𝑐 + 𝑟 sin 𝜃 3.26
… Circle-Generating Algorithms (Cont’d)
97
98. Bresenham's Line Algorithm:
Example: To illustrate the algorithm, we digitize the line with endpoints (20, 10) and (30, 18). This line has a slope
of 0.8, with 𝚫𝒙= 10, 𝚫𝐲 = 𝟖, The initial decision parameter has the value 𝑝0 = 2Δ𝑦 − Δ𝑥 = 6 and the increments for
calculating successive decision parameters are 𝟐𝚫𝒚 = 16, 𝟐𝚫𝒚 − 𝟐𝜟𝒙 = −𝟒.
We plot the initial point (𝒙 𝟎, 𝒚 𝟎) = (20, l0), and determine successive pixel positions along the line path from the
decision parameter as
…Line-Drawing Algorithms(Cont’d)
98
k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1) k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1)
0 6 (21,11) 5 6 (26,15)
1 2 (22,12) 6 2 (27,16)
2 -2 (23,12) 7 -2 (28,16)
3 14 (24,13) 8 14 (29,17)
4 10 (25,14) 9 10 (30,18)
99. Bresenham's Line Algorithm:
Example: To illustrate the algorithm, we digitize the line with endpoints (20, 10) and (30, 18). This line has a slope
of 0.8, with 𝚫𝒙= 10, 𝚫𝐲 = 𝟖, The initial decision parameter has the value 𝑝0 = 2Δ𝑦 − Δ𝑥 = 6 and the increments for
calculating successive decision parameters are 𝟐𝚫𝒚 = 16, 𝟐𝚫𝒚 − 𝟐𝜟𝒙 = −𝟒.
We plot the initial point (𝒙 𝟎, 𝒚 𝟎) = (20, l0), and determine successive pixel positions along the line path from the
decision parameter as
…Line-Drawing Algorithms(Cont’d)
99
k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1) k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1)
0 6 (21,11) 5 6 (26,15)
1 2 (22,12) 6 2 (27,16)
2 -2 (23,12) 7 -2 (28,16)
3 14 (24,13) 8 14 (29,17)
4 10 (25,14) 9 10 (30,18)
100. Bresenham's Line Algorithm:
Example: To illustrate the algorithm, we digitize the line with endpoints (20, 10) and (30, 18). This line has a slope
of 0.8, with 𝚫𝒙= 10, 𝚫𝐲 = 𝟖, The initial decision parameter has the value 𝑝0 = 2Δ𝑦 − Δ𝑥 = 6 and the increments for
calculating successive decision parameters are 𝟐𝚫𝒚 = 16, 𝟐𝚫𝒚 − 𝟐𝜟𝒙 = −𝟒.
We plot the initial point (𝒙 𝟎, 𝒚 𝟎) = (20, l0), and determine successive pixel positions along the line path from the
decision parameter as
…Line-Drawing Algorithms(Cont’d)
100
k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1) k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1)
0 6 (21,11) 5 6 (26,15)
1 2 (22,12) 6 2 (27,16)
2 -2 (23,12) 7 -2 (28,16)
3 14 (24,13) 8 14 (29,17)
4 10 (25,14) 9 10 (30,18)
101. Bresenham's Line Algorithm:
Example: To illustrate the algorithm, we digitize the line with endpoints (20, 10) and (30, 18). This line has a slope
of 0.8, with 𝚫𝒙= 10, 𝚫𝐲 = 𝟖, The initial decision parameter has the value 𝑝0 = 2Δ𝑦 − Δ𝑥 = 6 and the increments for
calculating successive decision parameters are 𝟐𝚫𝒚 = 16, 𝟐𝚫𝒚 − 𝟐𝜟𝒙 = −𝟒.
We plot the initial point (𝒙 𝟎, 𝒚 𝟎) = (20, l0), and determine successive pixel positions along the line path from the
decision parameter as
…Line-Drawing Algorithms(Cont’d)
101
k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1) k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1)
0 6 (21,11) 5 6 (26,15)
1 2 (22,12) 6 2 (27,16)
2 -2 (23,12) 7 -2 (28,16)
3 14 (24,13) 8 14 (29,17)
4 10 (25,14) 9 10 (30,18)
102. Bresenham's Line Algorithm:
Example: To illustrate the algorithm, we digitize the line with endpoints (20, 10) and (30, 18). This line has a slope
of 0.8, with 𝚫𝒙= 10, 𝚫𝐲 = 𝟖, The initial decision parameter has the value 𝑝0 = 2Δ𝑦 − Δ𝑥 = 6 and the increments for
calculating successive decision parameters are 𝟐𝚫𝒚 = 16, 𝟐𝚫𝒚 − 𝟐𝜟𝒙 = −𝟒.
We plot the initial point (𝒙 𝟎, 𝒚 𝟎) = (20, l0), and determine successive pixel positions along the line path from the
decision parameter as
…Line-Drawing Algorithms(Cont’d)
102
k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1) k 𝑝 𝑘 (𝒙 𝒌 +1, 𝒚 𝒌+ 1)
0 6 (21,11) 5 6 (26,15)
1 2 (22,12) 6 2 (27,16)
2 -2 (23,12) 7 -2 (28,16)
3 14 (24,13) 8 14 (29,17)
4 10 (25,14) 9 10 (30,18)