Simplest algorithm for zooming an image in Python by K factor

Question

I'm a total newbie to Python.

What's the simplest algorithm by which I can zoom an image by a factor of 3? I don't want to use the already made zoom functions available.

Answer 1

The task is moderately cumbersome, so I have shown a simple way to implement row zooming. You can similarly modify the indexes to implement column indexing for new_image as well.

# loading the image
from PIL import Image
import numpy as np
image = np.asarray( Image.open("img.jpg") )
import matplotlib.pyplot as plt

# create new image of correct size
m = len(image[0])
n = len(image)
factor = 3
new_image = np.zeros((factor*(n-1) + 1,factor*(m-1) + 1,3), dtype=int)

# implement row zooming
for i in range(n):
    row = image[i]
    for k in range(len(row)-1):
        new_image[i][k*factor], new_image[i][(k+1)*factor] = row[k], row[k+1]
        for mode in range(3):
            # need mode as three colour channels in RGB

            lo = int(min(row[k][mode], row[k+1][mode]))
            hi = int(max(row[k][mode], row[k+1][mode]))
            diff = int((hi-lo)//factor)
            for x in range(factor-1):
                new_image[i][k*factor+1+x][mode] = lo + (x*diff)