Session 16

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Session 16

• Scaling

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What can I do when things arent the size I want?

• Scaling Down My camera takes photos at 2304 x
  1708 pixels. That is WAY too big for posting to
  my website (where 300 x 200 would still be a good
  sized picture).

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Scaling Down a Picture

• passionFlower.jpg is 640pixels wide and 480
  pixels high
• If we copy every other pixel we will have a new
  picture with width (640 / 2 320) and height
  (480 / 2 240)

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Scaling Down Algorithm (different from that in
book)

• Create an instance of the source picture
• Invoke the method on the source picture
• Create the new target picture at half size
• Loop with x starting at 0 and as long as
  x
  through the loop.
• Loop with y starting at 0 and as long as y target height, increment y by 1 each time through
  the loop
• For each x,y value in the target picture, copy
  the pixel from x2,y2 from the source picture

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• public Picture scaleDown()
• Picture other new Picture(this.getWidth()/2
  , this.getHeight()/2)
• Pixel source null
• Pixel target null
• for (int x0 x
• for (int y0 y
• source getPixel(x2,y2)
• target other.getPixel(x,y)
• target.setColor(source.getColor())
• return other

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Trying the scaleDown() method

• Create an instance of the original photo
• Picture p new Picture(FileChooser.getMediaPath(
  minol.jpg))
• Invoke the scaleDown() method, capturing the
  result
• Picture p1 p.scaleDown()
• Show the result
• p1.show()

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Do you see any potential problems with this
algorithm?

• public Picture scaleDown()
• Picture other new Picture(this.getWidth()/2
  , this.getHeight()/2)
• Pixel source null
• Pixel target null
• for (int x0 x
• for (int y0 y
• source getPixel(x2,y2)
• target other.getPixel(x,y)
• target.setColor(source.getColor())
• return other

What happens if width or height is an odd number?
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A simple fix

• public Picture scaleDown()
• Picture other new
• Picture((this.getWid
  th()1)/2,(this.getHeight()1)/2)
• Pixel source null
• Pixel target null
• for (int x0 x
• for (int y0 y
• source getPixel(x2,y2)
• target other.getPixel(x,y)
• target.setColor(source.getColor())
• return other

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What can I do when things arent the size I want?

• Scaling Up Yesterday, Ashley had a photo of
  Paris Hilton she wanted to make bigger so she
  could put a pigs head on her body.

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Thinking Through Scaling Up
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• Copy each pixel in the source multiple times to
  the target
• Source (0,0) Target (0,0)
• Source (0,0) Target(1,0)
• Source (1,0) Target(2,0)
• Source (1,0) Target(3,0)
• Source (2,0) Target(4,0)
• Source (2,0) Target(5,0)
• Source (0,0) Target(0,1)
• Source (0,0) Target(1,1)

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Scaling Up Algorithm (again, different)

• Create the source picture
• Invoke the method on the source picture
• Create the target picture at twice the size
• Loop with source x starting at 0 and target x
  starting at 0 as long as
• Increment the source x by 0.5 each time through
  the loop, increment the target x by 1
• Loop with source y starting at 0 and target y
  starting at 0 as long as
• Increment the source y by 0.5 each time through
  the loop, increment the target y by 1
• Copy the color from the source to target pixel

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• public Picture scaleUpBlocks()
• Picture other new Picture(this.getWidth()2,
  this.getHeight()2)
• Pixel source null, target null
• for (int x0 x
• for (int y0 y
• source getPixel(x,y)
• target other.getPixel(x2,y2)
• target.setColor(source.getColor())
• target other.getPixel(x21,y2) //to
  the right
• target.setColor(source.getColor())
• target other.getPixel(x2,y21)
  //below
• target.setColor(source.getColor())
• target other.getPixel(x21,y21)
  //diagonal right and below
• target.setColor(source.getColor())

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Trying the scaleUpBlocks() method

• Create an instance of the original photo
• Picture p new Picture(FileChooser.getMediaPath(
  butterfly.jpg))
• Invoke the scaleDown() method, capturing the
  result
• Picture p1 p.scaleUpBlocks()
• Show the result
• p1.show()

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Can you think of a less blocky way to do this?

• Average two adjoining Pixels to come up with a
  brand new Pixel between them
• Has strengths and weaknesses as an overall
  solution

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• public Picture scaleUpAverage()
• Picture other new Picture(this.getWidth()2-
  1,this.getHeight()2-1)
• Pixel one null
• Pixel two null
• Pixel target null
• for (int x0 x
• for (int y0 y
• one getPixel(x,y)
• target other.getPixel(x2,y2)
• target.setColor(one.getColor())
• two getPixel(x1,y)
• target other.getPixel(x21,y2)
• target.setColor(new Color (
  (one.getRed()two.getRed())/2,
• (one.getGreen()two.
  getGreen())/2,
• (one.getBlue()two.g
  etBlue())/2 ))

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• two getPixel(x1,y1)
• target other.getPixel(x21,y21)
• c.setColor(new Color (
  (one.getRed()two.getRed())/2,
• (one.getGreen()two.
  getGreen())/2,
• (one.getBlue()two.g
  etBlue())/2 ))
• two getPixel(x,y1)
• target other.getPixel(x2,y21)
• c.setColor(new Color (
  (one.getRed()two.getRed())/2,
• (one.getGreen()two.
  getGreen())/2,
• (one.getBlue()two.g
  etBlue())/2 ))
• return other