Assignment 29 — image manipulation

Due Tuesday, April 27

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Module cw.py

• Implement functions rotate() and find() to support producing a clockwise rotation of an image.

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Function rotate( original )

• Return the size of the new image when performing a clockwise transformation of original.

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Function find( nspot, nw, nh )

• Returns the counter-clockwise correspondent location of nspot in the original, where nw and nh are the dimensions of the new image

Clockwise rotation

• Observations

• The leftmost x-coordinate of an image is 0.

• The bottommost y-coordinate of an image of height h is h-1.

• Knowing the x-coordinate of a pixel in the new image tells you the y-coordinate of the source pixel in the original image.

• The distance of a pixel from the bottom of the new image is how far the source pixel is from the left in the new image.

• So, knowing the y-coordinate of a pixel in the new image tells you how to calculate the x-coordinate of the source pixel in the original image.

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Testing

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

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Background

 

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🦆 © 2022 Jim Cohoon

Resources from previous semesters are available.