chapter6.py

import cv2
import numpy as np


def stack_images(scale, img_array):
    rows = len(img_array)
    cols = len(img_array[0])
    rowsAvailable = isinstance(img_array[0], list)
    width = img_array[0][0].shape[1]
    height = img_array[0][0].shape[0]
    if rowsAvailable:
        for x in range(0, rows):
            for y in range(0, cols):
                if img_array[x][y].shape[:2] == img_array[0][0].shape [:2]:
                    img_array[x][y] = cv2.resize(img_array[x][y], (0, 0), None, scale, scale)
                else:
                    img_array[x][y] = cv2.resize(
                        img_array[x][y],
                        (img_array[0][0].shape[1], img_array[0][0].shape[0]),
                        None, scale, scale
                    )
                if len(img_array[x][y].shape) == 2: img_array[x][y]= cv2.cvtColor(img_array[x][y], cv2.COLOR_GRAY2BGR)
        imageBlank = np.zeros((height, width, 3), np.uint8)
        hor = [imageBlank]*rows
        hor_con = [imageBlank]*rows
        for x in range(0, rows):
            hor[x] = np.hstack(img_array[x])
        ver = np.vstack(hor)
    else:
        for x in range(0, rows):
            if img_array[x].shape[:2] == img_array[0].shape[:2]:
                img_array[x] = cv2.resize(img_array[x], (0, 0), None, scale, scale)
            else:
                img_array[x] = cv2.resize(
                    img_array[x],
                    (img_array[0].shape[1], img_array[0].shape[0]),
                    None, scale, scale
                )
            if len(img_array[x].shape) == 2: img_array[x] = cv2.cvtColor(img_array[x], cv2.COLOR_GRAY2BGR)
        hor = np.hstack(img_array)
        ver = hor
    return ver


img = cv2.imread("Resources/lena.png")
imgGray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
imgStack = stack_images(0.5, (
    [img, imgGray, img],
    [img, img, img]
))
cv2.imshow("ImageStack", imgStack)


# The downside of this method is that, it requires the number of channels in all the images to be equal,
# otherwise this method won't work. Also, we can't resize an image using this method, so the images might go out of
# the frame.
# imgHor = np.hstack((img, img))
# imgVer = np.vstack((img, img))
# cv2.imshow("Horizontal", imgHor)
# cv2.imshow("Vertical", imgVer)

cv2.waitKey(0)