Homework 26 – image manipulation

Due Friday, April 20

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Module do.py

• Complete the implementation of the eleven functions. They provide underlying support for coloring a picture from a digital coloring book. The module functions will be used by crayon.py in the next assignment to do the actual coloring.

• The term coordinate is often used below. A coordinate is a two-tuple for representing a pixel location. The first element of the tuple is the x part of the coordinate and the second element of the tuple is the y part of the coordinate. Suppose spot is a coordinate. We can get set sx to be its x part and sy to be its y part with the following statement.

sx, sy = spot

• The term color is also often used below. For our purposes, a color is a three-tuple representing an RGB value; that is, and amount of red, green, and blue. Suppose drawing is an Image, and spot is a coordinate. We can set sr, sg, and sb to be the red, green, and blue levels of the RGB color (pixel) at coordinate spot on drawing with the following statement.

sr, sg, sb = drawing.getpixel( spot )

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Function random_color()

• Returns a random RGB three-tuple, where each element of the tuple is a random integer value from the inclusive interval 0 ... 255 (i.e., there are base 256 integers). For example, code segment ^†

random.seed( 'cs' )

c1 = do.random_color()

random.seed( '1112' )

c2 = do.random_color()

print( c1, c2 )

should print

(104, 190, 51) (190, 230, 218)

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Function get_width( drawing )

• Returns the width of the Image represented by drawing. For example, code segment

ml_url = 'http://www.cs1112.org/images/ml.png'

tj_url = 'http://www.cs1112.org/images/tj.png'

ml = url.get_image( ml_url )

tj = url.get_image( tj_url )

w1 = do.get_width( ml )

w2 = do.get_width( tj )

print( w1, w2 )

should print

512 580

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Function get_height( drawing )

• Returns the height of the Image represented by drawing. For example, code segment

ml_url = 'http://www.cs1112.org/images/ml.png'

tj_url = 'http://www.cs1112.org/images/tj.png'

ml = url.get_image( ml_url )

tj = url.get_image( tj_url )

h1 = do.get_height( ml )

h2 = do.get_height( tj )

print( h1, h2 )

should print

765 664

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Function 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. For example, code segment

xy1 = ( 2, 4 );

xy2 = ( 3, 9 )

l1 = do.left( xy1 )

l2 = do.left( xy2 )

print( l1, l2 )

should print

(1, 4) (2, 9)

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Function 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. For example, code segment

xy1 = ( 2, 4 );

xy2 = ( 3, 9 )

r1 = do.right( xy1 );

r2 = do.right( xy2 );

print( r1, r2 )

should print

(3, 4) (4, 9)

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Function above( spot )

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

xy1 = ( 2, 4 );

xy2 = ( 3, 9 );

a1 = do.above( xy1 );

a2 = do.above( xy2 );

print( a1, a2 )

should print

(2, 3) (3, 8)

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Function below( spot )

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

xy1 = ( 2, 4 );

xy2 = ( 3, 9 );

b1 = do.below( xy1 );

b2 = do.below( xy2 );

print( b1, b2 )

should print

(2, 5) (3, 10 )

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Function is_inbounds( drawing, spot )

• Returns True or False whether coordinate spot is inbounds on the Image represented by drawing. Obervations.

• If the x- or y-coordinate of spot is negative, then spot is out of bounds.

• If the x- coordinate of spot is greater than or equal to the width of drawing, then spot is out of bounds.

• If the y- coordinate of spot is greater than or equal to the height of drawing, then spot is out of bounds.

• Otherwise, spot is inbounds.

For example, code segment

ml_url = 'http://www.cs1112.org/images/ml.png'

ml = url.get_image( ml_url )

w = do.get_width( ml )

h = do.get_height( ml )

xy1 = ( w // 2, h // 2 )

xy2 = ( w, h )

xy3 = ( -1, -1 )

i1 = do.is_inbounds( ml, xy1 )

i2 = do.is_inbounds( ml, xy2 )

i3 = do.is_inbounds( ml, xy3 )

print( i1, i2, i3 )

should print

True False False

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Function get_color( drawing, spot )

• If coordinate spot is inbounds on the Image represented by drawing, the function returns the color at spot in the drawing; otherwise, the function returns None. For example, code segment

ml_url = 'http://www.cs1112.org/images/ml.png'

ml = url.get_image( ml_url )

w = do.get_width( ml )

h = do.get_height( ml )

xy1 = ( w // 4, h // 5 )

xy2 = ( w, h )

xy3 = ( -1, -1 )

c1 = do.get_color( ml, xy1 )

c2 = do.get_color( ml, xy2 )

c3 = do.get_color( ml, xy3 )

print( c1, c2, c3 )

should print

(137, 128, 97) None None

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Function is_colorable( drawing, spot, bg=(255,255,255) )

• Returns True or False whether coordinate spot is a colorable pixel in drawing. To be colorable spot must be inbounds and equal to the background color bg. For example, code segment

ml_url = 'http://www.cs1112.org/images/ml.png'

ml = url.get_image( ml_url )

w = do.get_width( ml )

h = do.get_height( ml )

xy1 = ( w // 5, h // 4 )

xy2 = ( w, h )

xy3 = ( -1, -1 )

xy4 = ( w // 4, h // 5 )

b1 = do.is_colorable( ml, xy1 )

b2 = do.is_colorable( ml, xy2, (255, 0, 255 ) )

b3 = do.is_colorable( ml, xy3 )

c = ml.getpixel( xy4 )

b4 = do.is_colorable( ml, xy4, c )

print( b1, b2, b3, b4 )

should print

False False False True

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Function paint( drawing, spot, c, bg=(255,255,255) )

• If spot is a colorable pixel on drawing, then that pixel is set to c; otherwise, no action is taken. For example, code segment

ml_url = 'http://www.cs1112.org/images/ml.png'

ml = get.web_image( ml_url )

for y in range( 175, 220 ) :

  for x in range( 228, 235 ) :

  xy = ( x, y )

  bg = ml.getpixel( xy )

  do.paint( ml, xy, ( 255, 215, 0 ), bg )

get.popup( ml )

should produce

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†. The above code segments are bundled into snippets.py.

 

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