ITEC 109 2014spring ibarland

home—info—labs—exams—hws
—D2L—MediaSamples/—breeze (snow day)—tutor/PIs

lab28
looping over entire pictures

Last time, we saw how we can have a function which uses a for-loop, along with range, to modify a 30x100 swatch of a picture. Today, we'll follow up on that in a natural way:

• TODO: Write a function stripeAtX : pict, int → None which takes in a picture and a column-number (x-coordinate), and enpurples¹ the picture's entire column.

  To think on, before starting: what range of y-coordinates do you want to use — starting from                  and going up to the picture object's                 . Explore the menu JES Functions > Pictures to see if there is a function that can help give you the end of the range.

  hint: I suggest temporarily adding repaint at the end of this function, but then removing it once you have the function working. If somebody calls stripeAtX 300 times, they can call repaint when they're done; there is no reason to repaint the picture-object 300 times.

• TODO: Write a function rect : pict → None which takes in a picture, and enpurples the entire picture, and then repaints it.

  To think on, before starting: what range of y-coordinates do you want to use — starting from                  and going up to the picture object's                 . Explore the menu JES Functions > Pictures to see if there is a function that can help give you the end of the range.

  Here is a solution.

• Self-challenge: Write a function enpurpleRegion : picture, int, int, int, int → None which takes in a picture, the coordinates of a northwest corner, and a width&height, and enpurples that entire square.

  As a followup: once you have enpurpleRegion working, go back and change your previous two functions so that they still do xactly the same thing, but they are each one line long — a single call to the very-general enpurpleRegion.

• Self-challenge: Play with randrange : int → int (you must first import random). (For example, call randrange(3) a half-dozen times, in the interaction window, and also google its documentation.)

  Then: Write a function that enpurples a 10x10 square at a randomly-chosen location, in a picture-object. Write another function that does this 20 times.

px = getPixel( somePictureObject, someXCoord, someYCoord )
setRed(px, 255)
setBlue(px, 255)

home—info—labs—exams—hws
—D2L—MediaSamples/—breeze (snow day)—tutor/PIs

©2014, Ian Barland, Radford University Last modified 2014.Apr.29 (Tue)

Please mail any suggestions (incl. typos, broken links) to ibarlandradford.edu