Rectification of wavy image by edges

Question

I have an image like this:

and i want to transform the image so that the white space is rectified.

The desired output should look something like this:

Can you help me archive this?

user_2836621 · Answer

You can do it like this...

Open input image, make greyscale and threshold into Numpy array
Make output image same size as input, but fully black
Iterate over the columns of the image, finding the first and last white pixel in each column. Copy that column of pixels to output image centred on the horizontal centreline
Save result

#!/usr/bin/env python3

from PIL import Image
import numpy as np

# Open wavy image and make greyscale
i = Image.open('wavy.jpg').convert('L')

# Make Numpy version of input image and threshold at 128
i = np.array(i)
i = np.where(i>128, np.uint8(255), np.uint8(0)) 

# Make Numpy version of output image - all black initially
o = np.zeros_like(i)

h, w = i.shape

# Process each column, copying white pixels from input image
# ... to output image centred on horizontal centreline
centre = h//2
for col in range(w):
    # Find top and bottom white pixel in this column
    whites = np.nonzero(i[:,col])
    top = whites[0][0]    # top white pixel
    bot = whites[0][-1]   # bottom white pixel
    thk = bot - top       # thickness of sandwich filling
    # Copy those pixels to output image
    startrow = centre - thk//2
    o[startrow:startrow+thk,col] = i[top:bot,col]

Image.fromarray(o).save('result.png')

Rectification of wavy image by edges

1 Answers