Class 38 — Friday November

Image mash ups

It’s simply smashing — For visitors on the Lawn — If they watch their steps

---

Look both ways

• Back or ahead

---

Gallery

• Spring 2020 art exposition

---

Downloads

• Module mash.py

• Module smashing.py

---

Rounding

• Enough ducks

---

---

Basic photo-manipulation problem-solving Python function one more time

def manip( original, size, color, where ) :

  ''' Provide a pattern for image manipulation

  function size(): determines size of new image based on the original

  function color(): determines color of new image pixel based on an

  original pixel

  function where(): determines where on original to determine

  correspondent pixel for new image

  '''

  # set dimensions of the new image

  nw, nh = size( original )

  # get a new appropriately sized image

  new_image = Image.new( 'RGB', ( nw, nh ) )

  # fill in every pixel of the new image

  for nx in range( 0, nw ) : # consider every x value for the new image

  for ny in range( 0, nh ) : # in tandem with every y value for the image

  # set the spot to be filled in the new image

  nspot = ( nx, ny )

  # determine the corresponding spot of interest in the original

  ospot = where( nspot, original )

  # get the pixel at the ospot

  opixel = original.getpixel( ospot )

  # determine the pixel for the new image

  npixel = color( opixel )

  # set the nspot in the new image

  new_image.putpixel( nspot, npixel )

  # return the filled in new image

  return new_image

---

Module mash.py

• Supports the creation of a new image that is a mash up of two existing images — bg and fg. The new image has bg as its background. The pixels in fg that are dissimilar to the back screen color are copied on top of the background.

---

Primary function (already written)

• combine( bg, fg, sx, sy, back_screen )

• Returns mash up of background image bg and foreground image fg, where the pixels in fg that are dissimilar to back_screen are copied on top of the background.

• The mash up uses location (sx, sy) as the spot in the background to start the overlay of fg.

def combine( bg, fg, sx, sy, back_screen ) :

  bw, bh = bg.size # size of background image

  fw, fh = fg.size # size of foreground image

  copy = bg.copy() # get a copy of background image

  new_image = copy.convert( 'RGB' ) # to be the basis of new image

  for fx in range( 0, fw ) : # consider every (fx, fy)

  for fy in range( 0, fh ): # possibility of the new image

  fspot = ( fx, fy ) # name spot (fx, fy )

  fpixel = fg.getpixel( fspot ) # get fspot pixel on fg image

  nx = sx + fx # determine the shifted nspot on new image

  ny = sy + fy # to paint fpixel

  nspot = ( nx, ny )

  # check whether fpixel should be painted on new image at nspot

  if ( colorable( nspot, new_image, fpixel, back_screen ) ) :

  new_image.putpixel( nspot, fpixel )

  return new_image # return the mash up

---

Helpful constant (already defined)

• SIMILARITY_THRESHOLD = 85

• Usage: values v1 and v2 are considered similar if the difference between v1 and v2 is less than SIMILARITY_THRESHOLD.

• Note: the difference between values v1 and v2 is the absolute value of v1 - v2.

---

Functions to be written

• distance( p1, p2 )

• Returns the the sum of RGB differences between colors p1 and p2. That is, the sum of the p1 and p2 red-level difference, green-level difference, and blue-level difference.

---

• similar( p1, p2 )

• Returns True if the distance between pixels p1 and p2 is less than similarity threshold; otherwise, returns False.

---

• is_background( p, back_screen )

• Returns True if p is similar to the back_screen color; otherwise, returns False.

---

• inbounds( spot, img )

• Returns True if spot lies on img; otherwise, returns False. That is, it returns whether the x-value and y-value for spot are nonnegative, the spot x-value is less than img width, and the spot y-value is less than img height.

---

• colorable( spot, img, p, back_screen )

• Returns True if both spot is a location on img (i.e., inbounds) and color p is not similar to color back_screen; otherwise, returns False.

---

 

---

---

---

---

---

---

---

 

---

© 2020 Jim Cohoon

Resources from previous semesters are available.