Graphics, Number Systems

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Lecture 6

• Graphics, Number Systems

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Bit-map Graphics

• Similar to real painting on the canvas, there is
  no way to change something but paint over it.
• Bit-mapped graphics become ragged when you shrink
  or enlarge them.

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Painting Bit-Mapped Graphics

• Paint pixels on the screen with a pointing device
• Select painting tools from a tools palette
• Create bit-mapped graphics
• Realism of the images isdetermined by the amount
  ofmemory allocation per pixel
• Resolution is determinedby the density of pixels

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Painting Bit-Mapped Graphics

• The outlinedareas can befilled with acolor or
  witha pattern

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Digital Image ProcessingPhotographic Editing by
Computer

• You can edit high-resolution bit-mapped images
• Select editing toolsfrom a palette
• Alter digitizedphotographs andgraphics from
  paintprograms

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Image Formats

• BMP
• The bit-mapped file format used by Microsoft
  Windows.
• TIFF (Tagged Image File  Format)
• A standard file format for storing images as bit
  maps. It is used especially for scanned images
  because it can support any size, resolution, and
  color depth

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Image Formats (cont)

• GIF (Graphics Interchange Format)
• A standard for digitized images compressed with
  the LZW algorithm (not image-specific, can be
  used for any data, in Unix a command compress).
  Allows for features such a transparent
  background, animation. Used in the Internet for
  small icon-like images.

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Image Formats (cont)

• JPEG (Joint Photographic Experts Group)
• JPEG is designed for compressing either
  full-color or gray-scale digital images of
  "natural", real-world scenes. It does not work so
  well on non-realistic images, such as cartoons or
  line drawings. JPEG does not handle compression
  of black-and-white (1 bit-per-pixel) images or
  moving pictures. Used in the Internet for photos.

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Vector Graphics

• A vector image consist of objects such as lines,
  rectangles, circles, etc. that can be easily
  moved around and resized.
• An object is usually chosen by a mouse click, and
  could be resized by dragging its borders.
• Objects stay separate from each other all the
  time.

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Vector Graphics

• Such properties of an object as line thickness,
  color, fill pattern can be easily changed after
  the object was created.
• Several objects may be grouped in on composed
  object.
• A composed object can be broken down to the
  original objects it was made from.
• Objects can be arranged in several layers, so
  that they overlap in a defined manner.

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Drawing Object-Oriented Graphics

• Draw the shapesof objects with apointing device
• The paletteof drawingsoftware differsfrom that
  ofpainting software

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Drawing Object-Oriented Graphics

• Shapes
• Are stored as formulas (text) describing how to
  draw that shape the allows infinite resolution
  and requires less memory
• The shape formulas allow for infinite resolution
  of the image
• The shape formulas alsomean fewer memory demands

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Image Formats

• Formats of drawing programs (e.g. xfig)
• PostScript, PDF
• Graphics file format developed by Adobe Systems.
  Postscript is widely used on Unix for
  distributing and printing documents. Portable
  Document Format (PDF) is de-facto standard for
  documents in the Internet

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Painting Pixels vs.Drawing Object Shapes

• Painting pixels
• More control over textures,shading and fine
  detail
• Used to create screendisplays (for videogames,
  multimediapresentations, andWeb pages)

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Painting Pixels vs.Drawing Object Shapes

• Painting pixels
• Used for simulatingnatural paint media
• Used to embellishphotographic images

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Painting Pixels vs.Drawing Object Shapes

• Drawing object shapes
• Better choice for creating printed graphs,
  charts, and illustrations with clean lines and
  smooth shapes

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CAD/CAM From Picturesto Products

• Engineers,architect, and designersuse
  (computer-aided design) CADsoftware to designor
  manufactureproducts
• AutoCAD

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Screen shot

• In Linux it is possible to save an image of whole
  display, a fragment of the display or a window
  using Grab-feature in the xv-program.
• In Windows it is possible to take save an image
  of the currently active window by pressing
  ltAltgt-ltPrintScreengt, or of the whole display by
  pressing just ltPrintScreengt. The image is then
  place into clipboard, and can be pasted for
  example into a WordPerfect document or into Paint
  program.

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Number and Character Representation in Computers
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A Bit About Bits

• A bit (binary digit)
• is the smallest unit of information
• can have two values - 1 and 0.
• Binary digits, or bits, can represent numbers,
  codes, or instructions.

On
Off
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Bits as Numbers

• Binary number system - a system that denotes all
  numbers and combinations of two digits.
• The binary system uses two digits to represent
  the numbers 0 and 1.

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Bits, Bytes, and Buzzwords

• Common terms might describe file size or memory
  size
• Bit smallest unit of information
• Byte a grouping of eight bits of information
• K (kilobyte) about 1,000 bytes of information -
  technically 1024 bytes equals 1K of storage.

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Bits, Bytes, and Buzzwords

• MB (megabyte) about 1 million bytes of
  information
• GB (gigabyte) about 1 billion bytes of
  information
• TB (terabyte) about 1 million megabytes of
  information

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Decimal System

• Humans have 10 fingers count in DECIMAL  
• Numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
  13, 14, 15, ...
• Use 10 digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9  
• We know that 5304 5103310201014100
• Base 10

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Binary System

• BINARY numbers
• 0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001,
  1010, 1011, ....
• Written with only 2 digits "0" and "1"
• In the same way as for decimal, 1011 (binary)
  123022121120 11 (decimal)
• Base 2
• Converting from binary to decimal is simple, just
  as for 1011 above.

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Binary System (contd.)

• How to know if 1011 is in binary or in decimal?
  Subscripts are used to show the base 10112
  (binary number), 101110 (decimal number)
• Converting from decimal to binary a little bit
  more tricky, we skip this, check some book if you
  are interested.
• Large binary numbers are cumbersome to write

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Hexadecimal System

• Heavily used in modern computers to represent
  binary data
• Numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C,
  D, E, F, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
  1A, 1B, ...
• Base 16
• Again the same idea
• 1A16 116110160 2610

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Hex (cont.)

• Groups of 4 bits
• 4 bits 24 16 combinations... ... use digits
  0-9 and A, B, C, D, E, F
• Converting between binary and hex is
  straightforward
• 10111101112 gt 10  1111  0111 gt 10(2) 
  1111(F)  0111(7) gt 2F716

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Octal System

• Octal was used in computers with byte length of 6
  bits
• Numbers 0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13,
  14, 15, 16, 17, 20, ...
• Base 8
• Groups of 3 bits
• 3 bits 23 8 combinations... use digits 0-7

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Octal (cont.)

• Converting between binary and octal is
  straightforward 10111101112 gt 1 011 110 111 gt
  
• 1(1) 011(3) 110(6) 111(7) gt13678
• In UNIX chmod command takes absolute mode for
  file access rights in octal

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Example

• Decimal            Binary     
  Octal           Hex   (base 10)          (base
  2)    (base 8)       (base 16)      
  0                0000        0              0
        1                0001       
  1              1       2               
  0010        2              2      
  3                0011        3              3
        4                0100       
  4              4       5               
  0101        5              5      
  6                0110        6              6
        7                0111       
  7              7       8               
  1000       10              8      
  9                1001       11              9
        10               1010      
  12              A       11              
  1011       13              B      
  12               1100       14              C
        13               1101      
  15              D       14              
  1110       16              E      
  15               1111       17              F
• 35            10 0011      
  43              23     100          110
  0100      144              64      255       
  1111 1111      377              FF

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Bits as Codes

• ASCII - American Standard Code for Information
  Interchange - most widely used code, represents
  each character as a unique 7-bit code.

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Character Tables

• ISO Latin1
• 8-bit code
• Extension to ASCII (ASCII is compatible)
• Has characters for European languages
• Cyrillic
• A dozen of different encodings
• Mostly used
• KOI8 for UNIX
• Windows-1251
• Unicode (16 bits) includes ALL characters from
  ALL languages (!)
• Character Sets in browsers