Increase width/height of image(not resize) - python-3.x

Question

]From https://www.pyimagesearch.com/2018/07/19/opencv-tutorial-a-guide-to-learn-opencv/
I'm able to extract the contours and write as files.
For example I've a photo with some scribbled text : "in there".
I've been able to extract the letters as separate files but what I want is that these letter files should have same width and height. For example in case of "i" and "r" width will differ. In that case I want to append(any b/w pixels) to the right of "i" photo so it's width becomes same as that of "r"
How to do it in Python? Just increase the size of photo(not resize)
My code looks something like this:
# find contours (i.e., outlines) of the foreground objects in the
# thresholded image
cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
cv2.CHAIN_APPROX_SIMPLE)
cnts = imutils.grab_contours(cnts)
output = image.copy()
ROI_number = 0
for c in cnts:
x,y,w,h = cv2.boundingRect(c)
ROI = image[y:y+h, x:x+w]
file = 'ROI_{}.png'.format(ROI_number)
cv2.imwrite(file.format(ROI_number), ROI)
[][1

Answer 1

Here are a couple of other ways to do that using Python/OpenCV using cv2.copyMakeBorder() to extend the border to the right by 50 pixels. The first way simply extends the border by replication. The second extends it with the mean (average) blue background color using a mask to get only the blue pixels.
Input:
import cv2
import numpy as np
# read image
img = cv2.imread('i.png')
# get mask of background pixels (for result2b only)
lowcolor = (232,221,163)
highcolor = (252,241,183)
mask = cv2.inRange(img, lowcolor, highcolor)
# get average color of background using mask on img (for result2b only)
mean = cv2.mean(img, mask)[0:3]
color = (mean[0],mean[1],mean[2])
# extend image to the right by 50 pixels
result = img.copy()
result2a = cv2.copyMakeBorder(result, 0,0,0,50, cv2.BORDER_REPLICATE)
result2b = cv2.copyMakeBorder(result, 0,0,0,50, cv2.BORDER_CONSTANT, value=color)
# view result
cv2.imshow("img", img)
cv2.imshow("mask", mask)
cv2.imshow("result2a", result2a)
cv2.imshow("result2b", result2b)
cv2.waitKey(0)
cv2.destroyAllWindows()
# save result
cv2.imwrite("i_extended2a.jpg", result2a)
cv2.imwrite("i_extended2b.jpg", result2b)
Replicated Result:
Average Background Color Result:

Answer 2

In Python/OpenCV/Numpy you create a new image of the size and background color you want. Then you use numpy slicing to insert the old image into the new one. For example:
Input:
import cv2
import numpy as np
# read image
img = cv2.imread('i.png')
ht, wd, cc= img.shape
# create new image of desired size (extended by 50 pixels in width) and desired color
ww = wd+50
hh = ht
color = (242,231,173)
result = np.full((hh,ww,cc), color, dtype=np.uint8)
# copy img image into image at offsets yy=0,xx=0
yy=0
xx=0
result[yy:yy+ht, xx:xx+wd] = img
# view result
cv2.imshow("result", result)
cv2.waitKey(0)
cv2.destroyAllWindows()
# save result
cv2.imwrite("i_extended.jpg", result)