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'''
use bilinear interpolation to resize an image
https://www.brezeale.com/?p=812
'''
import numpy as np
from PIL import Image
def resizeImage(name):
img1 = Image.open(name)
old = np.asarray(img1) # convert to Numpy array
rows, cols, layers = old.shape
new = np.zeros((2 * rows - 1, 2 * cols - 1, layers))
print("original dimensions:", old.shape)
for layer in range(3):
new[:, :, layer] = resizeLayer(old[:, :, layer])
# convert the values to unsigned, 8-bit integers
new = new.astype(np.uint8)
print(" new dimensions:", new.shape)
img2 = Image.fromarray(new) # convert back to Image
newName = "big-" + name
img2.save(newName)
def resizeLayer(old):
rows, cols = old.shape
rNew = 2 * rows - 1
cNew = 2 * cols - 1
new = np.zeros((rNew, cNew))
# move old points
new[0:rNew:2, 0:cNew:2] = old[0:rows, 0:cols]
''' alternative approach
# something like this would be necessary in languages
# that don't support slicing
new = np.zeros( (2*rows - 1, 2*cols - 1) )
for r in range(rows) :
for c in range(cols) :
new[2*r, 2*c] = old[r,c]
rows, cols = new.shape
'''
# produce vertical values
new[1:rNew:2, :] = (new[0:rNew - 1:2, :] + new[2:rNew:2, :]) / 2
''' alternative approach
for r in range(1, rows, 2) :
for c in range(0, cols, 2) :
# top + bottom
new[r,c] = ( new[r-1,c] + new[r+1,c] ) // 2
'''
# produce horizontal values
new[:, 1:cNew:2] = (new[:, 0:cNew - 1:2] + new[:, 2:cNew:2]) / 2
''' alternative approach
for r in range(0, rows, 2) :
for c in range(1, cols, 2) :
# left + right
new[r,c] = ( new[r,c-1] + new[r,c+1] ) // 2
'''
# produce center values
new[1:rNew:2, 1:cNew:2] = (new[0:rNew - 2:2, 0:cNew - 2:2] +
new[0:rNew - 2:2, 2:cNew:2] +
new[2:rNew:2, 0:cNew - 2:2] +
new[2:rNew:2, 2:cNew:2]) / 4
''' alternative approach
for r in range(1, rows, 2) :
for c in range(1, cols, 2) :
# top + bottom + left + right
new[r,c] = ( new[r-1,c] + new[r+1,c] + new[r,c-1] + new[r,c+1] ) // 4
'''
return new
#################### main ####################
test = np.array([[10, 40], [30, 20]])
print(test)
test = resizeLayer(test)
print()
print(test)
# filename = 'book_fausett_small.jpg'
# resizeImage(filename)
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