Lecture5 graphics


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  • SCA3103 - Introduction to Multimedia Semester 2 02/03 Lecture 2
  • Lecture5 graphics

    1. 1. LECTURE 5THE USES OF IMAGES IN MULTIMEDIA Prepared By Razia Nisar Noorani 1
    2. 2. Objective What is an image? The types of image  Bitmap  Vector  3D models Hardware used to acquire / edit images Converting from one format to another 2
    3. 3. What is an image? An image is the graphical and visual representation of some information that can be displayed on a computer screen or printed out Images come in a variety of forms:  Photographs  Drawings  Paintings  Television and motion pictures  Semantics  Maps etc. 3
    4. 4. What is an image? Images show us the prominent features of the objects that they represent. These images are composed quite differently, each is an effective representation of its subject 4
    5. 5. What is an image? Images play an important part in multimedia  Navigation  User interface components  Help systems  Clip art 5
    6. 6. Image media types Images can be generally divided into two formats:  Bitmapped or raster images  Vector graphics or Metafile images Bitmapped images are stored as an array of pixels Vector graphics are stored as the set of graphic primitives required to represent the image 6
    7. 7. Bitmaps Image A pixel is the smallest element of resolution on a computer screen (Screen Resolution) A pixel is the basic unit of a digital images. Digital image is a picture that may be stored in, displayed on, processed by a computer. As mentioned, bitmap is composed of a matrix elements called pixels Each pixel can be in a specific colour and each pixel consists of two or more colors. 7
    8. 8. Bitmaps Image The range of these colours is known as the colour depth. The color depth determined “How much data in bits used to determined the number of colors”. Colour depth is measured in bits per pixel  Remember: a bit (binary digit) is either 1 or 0 and that there are eight bits in a byte 8
    9. 9. Colour depth1 bit per pixel = 2 colours (monochrome)2 bits per pixel = 4 colours4 bits per pixel = 16 colours8 bits per pixel = 256 colours Generally good enough for colour images16 bits per pixel = 65536 colours Better quality for photograph-like images, also known as high colour24 bits per pixel = >16 million possible colours Used to recreate photo realistic images, also known as true colour 9
    10. 10. Bitmaps Image The more colours that are allowed per pixel, the greater the size of the image The number of pixels is related to the size of file that required to store an image. Remember, two factors effect the size file bitmap are:  Resolution  Color Depth 10
    11. 11. Bitmapped imagesOriginal image Shown magnified 11
    12. 12. Calculating the size of a raster image width × height × colour depth size in bytes = 8 Where:  Width of the images measured in pixels  Height of the images measured in pixels  Colour depth is the number of bits used for color measured in bits per pixel Remember:  1024 bytes = 1 kilobyte (KB)  1024 kilobytes = 1 megabyte (MB) 12
    13. 13. Example A 640 x 480 pixel image in 24-bit colour would require how much disk space? 640 × 480 × 24 7372800 size in bytes = = 8 8 = 921600 bytes = 900KB 13
    14. 14. Popular bitmap formats Microsoft bitmap (.bmp)  Used in microsoft windows TIFF - Tagged Image File Format (.tif)  Used for faxing images (amongst other things) JPEG - Joint Photographic Expert Group (.jpg)  Useful for storing photographic images 14
    15. 15. Popular bitmap formats GIF - Graphics Interchange Format (.gif)  Used a lot on web sites PNG - Portable Network Graphics (.png)  A new format for web graphics PCD – Kodak photo CD  A new format for store image in a compressed form on a CD 15
    16. 16. Advantages and Disadvantages of using bitmap images Advantages  Convey detail of information quickly  Real life Disadvantages  Depend on a Resolution  Effect to the image quality  Size file is big 16
    17. 17. Software to create bitmap images Popular PC packages include:  Microsoft Paint  Included with microsoft windows  Microsoft PhotoDraw 2000  http://www.microsoft.com/office/photodraw/  Adobe Photoshop  http://www.adobe.com/products/photoshop/main.html  Paint Shop Pro  http://www.jasc.com/psp6.html  Macromedia Fireworks  http://www.macromedia.com/software/fireworks/productinfo/ 17
    18. 18. Vector images Vector images are stored as the set of graphic primitives required to represent the image A graphic primitive is a simple graphic based on drawing elements or objects such as shape  e.g. square, line, ellipse, arc, etc. The image consists of a set of commands (mathematical equations) that are drawn the object when needed. 18
    19. 19. Vector images Storing and representing images by mathematical equations is called vector graphics or Object Oriented graphics. Each primitive object has various attributes that go to make up the entire image  e.g. x-y location, fill colour, line colour, line style, etc. Example:  RECTANGLE : rectangle top, left, width, height, color is ( 0, 0, 200, 200, red) 19
    20. 20. Vector images  CIRCLE : circle top, left, radius, color  LINE : Line x1, y1, x2, y2, color Vector image or vector graphics can be resized without losing the integrity of the original image. Scaling a vector is a mathematical operation - only the attributes change, the image is unaffected Q: Could you defined what the different between a digital image and Computer Graphics or graphics? 20
    21. 21. Primitive geometric drawing objects Basic  Shapes  Line  Circle  Polyline  Ellipse  Arc  Rectangle  Bezier curve  Square  Pie segment  Triangle Text  Pentagon,  Font, weight hexagon, heptagon, octagon, etc Text Text 21
    22. 22. Scaling vector graphics ShownOriginal image magnified V e c to r g r a p h ic s V e c to r g r a p h ic s 22
    23. 23. Advantages and Disadvantages of using vector image Advantages  Relatively small amount of data required to represent the image.  Therefore, it does not required a lot of memory to store  Easier to manipulate Disadvantages  Limited level of detail than can be presented in an image 23
    24. 24. Software to create vector images Graphics programs are tools that allow an artist to create and edit designs used in multimedia applications. Generally, graphics programs can be categorized as: • Drawing programs – Creating draw type graphics – Provide freehand. Example geometric shape – Example : Adobe Illustrator, Corel Draw, Macromedia Freehand http://www.adobe.com/products/illustrator/main.html 24
    25. 25. Software to create vector images Paint programs - Those creating bitmaps - useful in creating original art - Example: Paint Shop Pro http://www.jasc.com/psp6.html Image editing programs - Making changes to existing images, such as manipulating the brightness or contrast, applying textures, patterns. - Examples : Adobe Photoshop, Adobe Page Maker, 25
    26. 26. Vector formats Windows metafile (.wmf)  Used by Microsoft Windows SVG - Scalable Vector Graphics (.svg)  A new format devised for the web CGM - Computer Graphics Metafile (.cgm)  Older format commonly used for clip art Adobe PostScript (.ps)  A page description language used to control printers 26
    27. 27. Vector formats Adobe Portable Document Format (.pdf)  A page description language common on the web Drawing Exchange Format (.dfx)  Store 3D image created by design program AutoCAD Encapsulated PostScript (.epf)  Professional printing: Illustration program, Adobe Systems, Desktop Publishing programs 27
    28. 28. 3-Dimensional Graphic models A 3D model is a variation on the vector format The location of a 3-dimensional object is specified using x, y and z co-ordinates X Further primitives can be found 3D model in 3D models  Cube, sphere, pyramid, etc.  Camera, spotlight, texture, shading Y etc. Z 28
    29. 29. 3-Dimensional Graphic models 3D graphics offer the photorealistics effects that have you seen in TV, Computer Games Examples, Motion Picture films such as:  Jurassic Park, Terminator 2, Lost World and Toy Story Examples 3D programs:  Carigali Truespace  3D Studio Max  Infini-D 29
    30. 30. 3-Dimensional Graphic models 30
    31. 31. 3-Dimensional Graphic models 31
    32. 32. Hardware used to acquire images Flatbed scanner Scanners and digital imaging products Many forms of scanner  Drum  Flat-bed  Negative / slide  Hand-held Important to check the optical resolution of the scanner  measured in dots per inch (DPI) Slide scanner 32
    33. 33. Hardware used to acquire images Digital camera Digital camera  Uses digital memory instead of film  Images are transferred to computer via a cable  Can be very high resolution Stills from a camcorder or PC “web-cam” type camera  Home products tend to be low resolution Web cam 33
    34. 34. Hardware used to create / edit images Tablet and pen Graphics tablet and pen  Preferred by digital artists  Pressure sensitivity Digitiser tablet  Preferred by technical artists  Mouse has accurate crosshair to help digitise drawings Digitiser 34
    35. 35. Converting image formats Bitmapped font Bitmapped image Bitmapped image TrueType / PostScript Vector image Vector image Type 1 fontTextText Render as bitmap Contour trace Optical Character Recognition (OCR) 35
    36. 36. Working With Graphics Considerations and guidelines when we are working with graphics:  Choose the graphic depend on your work  Choose the correct software  Use minimum color depth  Delivery Systems 36
    37. 37. How graphics/images can be used effectively Different types of graphics are used in different ways: Line drawing are graphical representations of physical objects. There are 3 kinds of line drawings:  Isometric - represent 3-D objects without realistic perspective  Orthographic - are 2-D representations of objects  Perspective - represent objects in their most realistic form 37
    38. 38. How graphics/images can be used effectively Graphs and Tables In just a glance, graphs can provide specific data, show general trends in data or depict the relationships between data and data trends Diagrams Help users conceptualize a process, flow or interrelationship. Examples of diagrams include: Flow charts, Schematic Drawings and Block Diagrams. 38
    39. 39. Advantages and Disadvantages of using images Advantages  Convey a lot of information quickly  Add visual simulation and colour  Can communicate across language borders  Enhance other media 39
    40. 40. Advantages and Disadvantages of using texts Disadvantages  Do not provide in-depth explanations  Graphics rarely suffice to convey a whole message in business, technical or safety settings  Can be misinterpreted  Graphics should be used carefully to make sure the message is not ambiguous or cryptic. 40
    41. 41. Summary Today we have met the various types of image that are useful when creating multimedia applications Pros and cons of bitmapped and vector images What hardware is used to create each of these 41
    42. 42. Next lecture...We will look at digital Audio formats 42