Scaling Part of a Picture

Question

I want to scale up a part of a picture, in this example, a nose.

I have a function to select the part of the picture I want to enlarge.

def copyAndPa         


        

Answer 1

This is just for the record and for fun, not an answer...

But as mentioned abarnert ("Are you sure they just want you to leave 3 white pixels for every copied pixel, rather than copying the same pixel 4 times?"), which is quite ridiculous as a scaling algorithm...

A lot more interesting yet basic approach to scale an image is the Nearest Neighbor Algorithm.

def EnlargeNearestNeighbor(picture, multiplier):

  w1 = getWidth(picture)
  h1 = getHeight(picture)
  w2 = getWidth(picture) * multiplier
  h2 = getHeight(picture) * multiplier

  x_ratio = w1/float(w2)
  y_ratio = h1/float(h2)

  newPicture = makeEmptyPicture(w2, h2)

  for x in range(0, w2):
    for y in range(0, h2):
      newPx = getPixel(newPicture, x, y)

      px = floor(x*x_ratio);
      py = floor(y*y_ratio);

      oldPx = getPixel(picture, int(px), int(py))
      setColor(newPx, getColor(oldPx))

  return newPicture

file = pickAFile()
picture = makePicture(file)
pic = EnlargeEagle(picture)

pic2 = EnlargeNearestNeighbor(picture, 3)

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Other interesting algorithms here.

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Here is a basic implementation of the Eagle Algorithm (works fine with images with a low number of different colors):

def EnlargeEagle(picture):

  w = getWidth(picture)
  h = getHeight(picture)
  w2 = getWidth(picture)*2
  h2 = getHeight(picture)*2

  newPicture = makeEmptyPicture(w2, h2)

  x2 = 0
  for x in range(1, w-1):
    y2 = 0
    for y in range(1, h-1):

      oldPxS = getPixel(picture, x-1, y-1)
      oldPxT = getPixel(picture, x, y-1)
      oldPxU = getPixel(picture, x+1, y-1)

      oldPxV = getPixel(picture, x-1, y)
      oldPxC = getPixel(picture, x, y)
      oldPxW = getPixel(picture, x+1, y)

      oldPxX = getPixel(picture, x-1, y+1)
      oldPxY = getPixel(picture, x, y+1)
      oldPxZ = getPixel(picture, x+1, y+1)

      newPx1 = getPixel(newPicture, x2, y2)
      newPx2 = getPixel(newPicture, x2+1, y2)
      newPx3 = getPixel(newPicture, x2, y2+1)
      newPx4 = getPixel(newPicture, x2+1, y2+1)

      # Step 1
      c = getColor(oldPxC)
      setColor(newPx1, c)
      setColor(newPx2, c)
      setColor(newPx3, c)
      setColor(newPx4, c)

      # Step 2      
      if (getColor(oldPxV) == getColor(oldPxS)) and (getColor(oldPxS) == getColor(oldPxT)):
         setColor(newPx1, getColor(oldPxS))

      if (getColor(oldPxT) == getColor(oldPxU)) and (getColor(oldPxU) == getColor(oldPxW)):
         setColor(newPx2, getColor(oldPxU))

      if (getColor(oldPxV) == getColor(oldPxX)) and (getColor(oldPxX) == getColor(oldPxY)):
         setColor(newPx3, getColor(oldPxX))

      if (getColor(oldPxW) == getColor(oldPxZ)) and (getColor(oldPxZ) == getColor(oldPxY)):
         setColor(newPx4, getColor(oldPxZ))



  y2 += 2
x2 += 2

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Original:

Nearest Neighbor:

Eagle:

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Enjoy!