Assignment 28 — image manipulation

Due Monday, November 28

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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

• Observations

• ( nw, nh ) equals ( oh, ow )

• The leftmost x-coordinate of the new image is 0.

• The rightmost x-coordinate of the new image is nw-1.

• The topmost y-coordinate of an image is 0.

• The bottommost y-coordinate of the new image is nh-1.

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

• The distance of a pixel from the righthand side of the new image is how far the source pixel is from the top in the new image. So, knowing the x-coordinate of a pixel in the new image tells you how to calculate the y-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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