Assignment 30 — image manipulation

Due Friday, April 17

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Downloads

• Module gray.py

• Module palette.py

• Module cw.py

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Clockwise rotation — module gray.py

• Your task is to implement two functions color() to support producing a grayscaling of an image.

• Function color( opixel )

• Returns a new pixel whose RGB values are (m, m, m) where m is is the integer cast of .299r + .587g + .114b, where r, g, and b are the RGB values of opixel.

• The module has built-in testing using a mandrill image.

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Clockwise rotation — module cw.py

• Your task is to implement two functions size() and where() to support producing a clockwise rotation of an image.

• Function size( original )

• Returns the dimensions of an image that would be a clockwise rotation of original.

• Function where( nspot, original )

• Return the correspondent of spot nspot in the original image when doing a clockwise transformation

• The module has built-in testing using a mandrill image.

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Palette reduction — module palette.py

• Your task is to implement functions distance() and color(). Before defining their purposes, first some context.

• Sometimes to save computer memory, software developers perform a palette reduction of colors used in image representation.

• Our reduction scheme will use an eight-color palette

• Black, White, Red, Green, Blue, Yellow, Magenta, and Cyan; that is, (0,0,0), (255,255,255), (255,0,0), (0,255,0), (0,0,255), (255,255,0), (255,0,255), and (0,255,255)

• In a palette reduction, a pixel (r,g,b) is replaced by the pixel in in the palette it is closest to. The distance between pixels (r1,g1,b1) and (r2,g2,b2) equals

abs(r1 - r2) + abs(g1 - g2) + abs(b1 - b2)

• Note there is built-in function abs() for calculating absolute values.

• Function distance( p1, p2 )

• Returns the distance between pixels p1 and p2; that is the sum of the red differences, green differences, and blue differences, where difference is an absolute value.

• Function color( opixel )

• Make use of the color palette PALETTE8

PALETTE8 = [ ( 0, 0, 0), (255,255,255), ( 0,255, 0), ( 0, 0,255),

  (255, 0, 0), (255,255, 0), (255, 0,255), ( 0,255,255) ]

• Returns the pixel in PALETTE8 that opixel is closest to

• The module has built-in testing using a mandrill image.

 

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© 2020 Jim Cohoon

Resources from previous semesters are available.