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Enlarging an Image

Applying the Seven-step Proces

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Double Size of Image

• Problem: double image size

• Twice width + height

• 7 Steps

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Step 1: Small Instance by Han

• 2x2 ! 4x4 

inImage outImage

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Step 2: Write Down Steps

inImage

I started with the image I wanted (inImage)1

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Step 2: Write Down Steps

inImage outImage

I made a blank image (outImage) twice as wideand twice as tall as inImage

2

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Step 2: Write Down Steps

inImage outImage

I made outImage’s 1st pixel red3

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Step 2: Write Down Steps

inImage outImage

I made outImage’s 2nd pixel red4

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Step 2: Write Down Steps

inImage outImage

I made outImage’s 3rd pixel blue5

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Step 2: Write Down Steps

inImage outImage

I made outImage’s 16th pixel purple18

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Step 2: Write Down Steps

I started with the image I wanted (inImage)1

I made a blank image (outImage)twice as wide and twice as tall as inImage

2

I made outImage’s 1st pixel red3

I made outImage’s 2nd pixel red4

I made outImage’s 3rd pixel blue5

I made outImage’s 4th pixel blue6

I made outImage’s 5th pixel red7

I made outImage’s 6th pixel red8

I made outImage’s 7th pixel blue9

I made outImage’s 8th pixel blue10

… 9th pixel green11

…10th pixel green12

…11th pixel purple13

…12th pixel purple14

…13th pixel green15

…14th pixel green16

…15th pixel purple17

…16th pixel purple18

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Step 3: Find Patterns

I made outImage’s 1st pixel red3

I made outImage’s 2nd pixel red4

I made outImage’s 3rd pixel blue5

I made outImage’s 4th pixel blue6

I made outImage’s 5th pixel red7

I made outImage’s 6th pixel red8

I made outImage’s 7th pixel blue9

I made outImage’s 8th pixel blue10

… 9th pixel green11

…10th pixel green12

…11th pixel purple13

…12th pixel purple14

…13th pixel green15

…14th pixel green16

…15th pixel purple17

…16th pixel purple18

Look for repetitions and patterns

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Step 3: Find Patterns

I made outImage’s 1st pixel red3

I made outImage’s 2nd pixel red4

I made outImage’s 3rd pixel blue5

I made outImage’s 4th pixel blue6

I made outImage’s 5th pixel red7

I made outImage’s 6th pixel red8

I made outImage’s 7th pixel blue9

I made outImage’s 8th pixel blue10

… 9th pixel green11

…10th pixel green12

…11th pixel purple13

…12th pixel purple14

…13th pixel green15

…14th pixel green16

…15th pixel purple17

…16th pixel purple18

Look for repetitions and patterns

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Step 3: Find Patterns

I made outImage’s 1st pixel red3

I made outImage’s 2nd pixel red4

I made outImage’s 3rd pixel blue5

I made outImage’s 4th pixel blue6

I made outImage’s 5th pixel red7

I made outImage’s 6th pixel red8

I made outImage’s 7th pixel blue9

I made outImage’s 8th pixel blue10

… 9th pixel green11

…10th pixel green12

…11th pixel purple13

…12th pixel purple14

…13th pixel green15

…14th pixel green16

…15th pixel purple17

…16th pixel purple18

Look for repetitions and patterns

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Step 3: Find Patterns

I made outImage’s 1st pixel red3

I made outImage’s 2nd pixel red4

I made outImage’s 3rd pixel blue5

I made outImage’s 4th pixel blue6

I made outImage’s 5th pixel red7

I made outImage’s 6th pixel red8

I made outImage’s 7th pixel blue9

I made outImage’s 8th pixel blue10

… 9th pixel green11

…10th pixel green12

…11th pixel purple13

…12th pixel purple14

…13th pixel green15

…14th pixel green16

…15th pixel purple17

…16th pixel purple18

Look for repetitions and patterns

d

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Step 3: Find Patterns

• Find pattern in

pixel used

0 1 2 3

0

1

2

3

0 1

0

1

To color pixel

with x = …

Look at pixel

with x = …0

1

2

3

0

0

1

1

S i d

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Step 3: Find Patterns

• Divide by 2 is close

• But only want integer part

• Similar pattern for y’s

To color pixel with x

Look at pixelwith x = …

0 0

1 0

2 1

3 1

 x/2

0

0.5

1

1.5

0

0

1

1

 floor(x/2)

S 3 Fi d P

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Step 3: Find Patterns

I made a blank image (outImage) twice as wideand twice as tall as inImage

2

I started with the image I wanted (inIMage)1

For each pixel in outImage:3

Computed x=floor(pixel’s x/2)a

Computed y=floor(pixel’s y/2)b

Set pixel to the same color asthe pixel at (x,y) in inImage

c

S 4 T Al i h

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Step 4: Test Algorithm

I started with the image I wanted (inImage)1

I made a blank image (outImage)twice as wide and twice as tall as inImage

2

For each pixel in outImage:3

Computed x=floor(pixel’s x/2)a

Computed y=floor(pixel’s y/2)b

Set to the same color as thepixel at (x,y) in inImage

c

Now it’s your turn.

Think about if your

answer is right

 Yes. Answer is right!Now let’s write code