Assignment 29 — coloring within the lines

Due Friday, December 2

---

Module crayon.py

• Complete the implementation of functions flood() and sweep()

• For this assignment we are interested in auto-coloring a user-specified coloring book page.

       

• Everyone of the elements comprising a page will be assigned its own random color. All unpainted spots in a particular element, will be painted using that color. The function managing the painting of an element is flood(). If the starting point for a new flooding is already colored, then function flood() simply returns.

• Function sweep() has responsibility for making sure all of the elements of a page are colored. Going from left-to-right, top-to-bottom, it will examine the current spot. If the spot is unpainted, it will generate a random color and flood that spot's element with the just generated color. If the current spot Is already painted, sweep() goes on to its next spot.

• The two functions should make use of module do.py to assist with the coloring. It provides the following functions

• def random_color() :

• Returns a random RGB three-tuple, where each element of the tuple is a random integer value from the interval 0 ... 255.

• def get_width( page ) :

• Returns the width of the Image represented by page.

• def get_height( page ) :

• Returns the height of the Image represented by page.

• def left( spot ) :

• Returns the coordinate immediately left of spot; that is, its x-coordinate is one less than that of spot and its y-coordinate is the same as that of spot.

• def right( spot ) :

• Returns the coordinate immediately right of spot; that is, its x-coordinate is one greater than that of spot and its y-coordinate is the same as that of spot.

• def above( spot ) :

• Returns the coordinate immediately above spot; that is, its y-coordinate is one less than that of spot and its x-coordinate is the same as that of spot.

• def below( spot ) :

• Returns the coordinate immediately below spot; that is, its y-coordinate is one greater than that of spot and its x-coordinate is the same as that of spot.

• def is_inbounds( page, spot ) :

• Returns True or False depending whether coordinate spot is inbounds on the image represented by page.

• def get_color( page, spot ) :

• If coordinate spot is inbounds on the image represented by page, the function returns the color at spot in the page; otherwise, the function returns None.

• def is_colorable( page, spot, bg ) :

• Returns True or False depending whether coordinate spot is a colorable pixel in image page. To be colorable spot must be inbounds and equal to the background color bg.

• def paint( page, spot, c, bg) :

• If spot is a colorable pixel on image page, then that pixel is set to c; otherwise, no action is taken.

---

Flooding visualization

• Slides

• Slides exported as PDF

• Slides exported as MP4

---

Function flood( page, spot, c, bg )

• If spot is not a colorable pixel on page, then no action is taken.

• If instead spot is a colorable pixel on page, then all pixel locactions reachable from spot traversing only colorable pixels are set to color c.

• The function does not return a value

• Visualization of how flood() should work is available above.

• (Highly) recommended algorithm

 If the spot on the page is not colorable

  return

 Color the spot using c

 Create a to-do list with spot as its element

 While the to-do list is not empty

  Pop an element from the to-do list and assign it to v

  If v’s left is empty, paint it and add to to-do list

  If v’s right is empty, paint it and add to to-do list

  If v’s above is empty, paint it and add to to-do list

  If v’s below is empty, paint it and add to to-do list

---

Function sweep( spot, bg )

• For every bg colorable spot pixel, a flood() is performed. For each flooding a new random color is used.

• The function does not return a value.

• My implementation considers the rows of pixels making up a picture from top to bottom. Within a row, the pixels were considered left to right. If you do a different order, your picture could look different. Also, my implementation generates a random color only if the pixel under consideration is colorable.

page_width = do.get_width( page )

page_height = do.get_height( page )

for px in range( 0, page_width ) :

  for py in range( 0, page_height ) :

  spot = (px, py) # spot is the current drawing coordinate of

  # interest.

  # if the pixel at spot is colorable, generate a random color

  # and start a flood from there

  pass

---

Coloring examples

       

       

       

       

       

       

 

---