Communicating Quantitative Information

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Communicating Quantitative Information

• Go over midterm
• Is a picture worth 1000 words?
• Digital images. Number bases
• Standards, Compression
• Will your images last?
• Homework (Post project proposal). Work on
  Project.NEXT CLASS in computer classroom

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Midterm

• Will use results for lesson in frequency
  distributions and graphs (Excel)
• Final will be similar
• preparation guide
• you can prepare a set of notes
• cumulative

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Digital images

• Basic encoding
• Is a picture worth 1000 words?
• Standards
• bmp, gif, jpg
• Preservation issue
• will the files last on storage medium
• will there be appropriate software to display and
  manipulate the image

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Basic encoding

• Divide image into picture elements (pixels)
• For each pixel (cell in the grid), record color
• Different color spaces
• palette-based
• RGB (redness, greenness, blueness)
• YUV (Ybrightness, U and V together are hue and
  saturation)
• other

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Digital cameras marketing

• More pixels (increased resolution) means that
  pictures can be 'blown up' more without showing
  pixelations
• If you are NOT planning to make poster size
  pictures, you don't need more than 3megalpel? 5
  megalpel?
• cameras now competing on features like modes

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Palette based

• Think of painter's palette
• Can only use those colors
• If no match
• painter mixes up something (creates a new color
  on palette)
• computer software dithers
• produces spots of different colors that,
  hopefully, our eyes mix together to see desired
  color.

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The software constructs palettewhen saving this
image using a format with limited palette
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Image file

• Simple bit mapped, palette
• (may include the palette, with general
  representation of the colors)
• string of numbers, one for each pixel, indicating
  how that pixel is to be painted

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Contrast

• Painter (in smock) starts with palette
• Computer software (PhotoShop, Paint Shop Pro,
  etc. doing conversions) can construct the best
  palette for a given photo

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Encoding

• Image file is all numbers!!
• Actually, all bits (sequences of 1s and 0s)
• Suppose, palette is black and white
• 0 could stand for white
• 1 could stand for black
• Suppose, palette holds 4 colors
• 00, 01, 10, 11 represent 4 distinct colors
• Suppose, palette holds 256 colors
• 00000000, 00000001, . 11111111 There are 256
  distinct patterns of 8 1s and 0s.

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Quick exercise

• How many different patterns can be made using 0s
  and 1s, 3 bits long? Make a list
• 000

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General formula

• Space N bits can hold 2N distinct patterns
• 1 bit can hold 2 distinct patterns (represent 2
  colors) 21
• 2 bits can hold 4 distinct patterns (represent 4
  colors) 22
• 3 bits can hold 8 distinct patterns 23
• 8 bits can hold 28

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Image file size

• Say image is 300 by 400 pixels (300 wide, 400
  high)
• Each pixel is 8 bits (so the picture can have 256
  colorsnot especially big)
• Say there is no compression (will get to this
  later)
• Size is 300 400 8 bits
• 960000 bits

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1000 words

• (Plain text file, not Word document)
• How big is a word? Assume it averages out to 6
  letters.
• How many bits does a letter require?
• In the standard encoding, 8 bits.
• 1000 words occupies 1000 6 8 48000 bits

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Is a picture worth 1000 words?

• Answer it better because it costs/takes
  considerably more space.
• compression reduces image sizes, but only so much

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For purple hat
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Digital camera

• Uses a (large) palette
• Records a number for what will be each pixel
• There may be settings for color depth (amount of
  bits numbers of colors) and resolution (size of
  pixel)

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Standards (briefly)

• gif uses common strings, so repeated patterns do
  get compressed
• compression is lossless. Can restore full
  detail.
• restricted to 256 colors
• Good for line art
• jpg uses common areas, but in a different color
  space and a different way (approximates changes
  in 8 by 8 blocks). For example, detects common
  levels of brightness.
• compression is lossy. Cannot restore full detail.
• can hold millions of colors 8 bits for each of
  YUV.
• Good for photographs

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Number bases

• Refresher we use the decimal system base 10
• 10 distinct symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
• Base system
• first column on the left is the ones/unit place
  (100)
• second column starting from the left is the 10s
  place (101)
• third column is the 100th place (102)
• and so on

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Base 2

• Binary number system
• have 2 symbols 0 and 1. These are called bits!
• Base system
• first column on the left is the ones/unit place
  (20)
• second column is the 2-place (21)
• third column is the 4-place (22)
• and so on
• Fewer symbols (simpler circuitry), longer strings
  of symbols needed

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Warning

• bit is either a 0 or a 1. Abbreviation b
• byte is 8 bits. Abbreviation B
• k may mean 1000 or 1024 (a power of 2)
• Mega-bit, Mega-byte, Mega-pel
• 1000000 bits, bytes or pixels
• Gigabyte 1000000000

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Base 16

• Hexadecimal
• 16 symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B,
  C, D, E, F.
• first column is the 1s place
• second column is the 16th place
• third column is the 256th place
• and so on.

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Exercise

• Write your age in
• decimal
• binary
• hexadecimal
• How many 16s are there (probably just 1)?
• What is left over?

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Use of Hexadecimal

• RGB colors
• Each of red, green, blue is allocated 8 bits
  takes up 2 hexadecimal digits (bad term)
• Deep red is FF0000
• Deep blue is 0000FF
• white is FFFFFF
• black is 000000

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Will digital images last

• Depends on
• storage medium. Hard disks can fail. CDs and DVDs
  can get damaged. Memory sticks fairly robust,
  but ends can get damaged (and they can get lost)
• software Need software that 'knows' the standard
  used for the picture
• Software for display, manipulation, printing

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Linear Perspective

• Perspectivea technique for representing
  three-dimensional space on a flat surface.

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Linear perspective

• is based on the way the human eye sees the
  worldobjects which are closer appear larger, and
  more distant objects appear smaller.
• Objects are drawn using orthogonal lines which
  lead to the vanishing point(s).

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Linear perspective

• In one-point perspective, the forms are seen face
  on and are drawn to a single vanishing point.
• Objects seen at an angle would be drawn with
  two-point perspective using two vanishing points.
  

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One-point perspective
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Turn your paper horizontal ("landscape"
orientation)
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Draw a horizontal line
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Draw your vanishing point.
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Now draw a square or a rectangle
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Draw orthogonals
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Draw a horizontal line
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Draw a vertical line
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Erase the remaining orthogonals.
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Add details and experiment!
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Add details and experiment!
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Add details and experiment!
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Add details and experiment!
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(No Transcript)
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Other perspectives

• Cameras can supply other perspectives, depending
  on point of focus
• Suitable topic for Project 2
• See next several charts for 2-point perspective
• (I will skip to next topic).

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Two-points Perspective
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Draw your horizon line.
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Draw your vanishing points
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Draw the "front edge" of your form.
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Draw your orthogonals
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Draw two vertical lines between the orthogonals
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Complete the top of the form
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Erase the extra orthogonals.
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Now add details and experiment!
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Now add details and experiment!
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Now add details and experiment!
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Now add details and experiment!
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Compare!
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Compare!
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Compare
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Hobemma
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Vincent van Gogh
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Giotto. Annunciation to S. Anna. XIV s.
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Three-point perspective
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Four-point perspective
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Five-point perspective
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Six-point perspective
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N-points perspective
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Reverse Perspective
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Reverse Perspective
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Reverse Perspective
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Reverse Perspective
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Reverse Perspective
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Reverse Perspective
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Reverse Perspective
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Sound

• Sound files also use different standards.
• Wav (different parameters)
• mpeg
• Same issue regarding archiving
• Storage needs to remain
• Software to manipulate and play needs to be
  available

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Homework

• Project I
• Postings
• Posting topic problems in archiving digital
  images
• Old issue major patent dispute concerning gif
• REMEMBER next class in computer classroom for
  Excel work