Center Crop and Image Scaling functions in OpenCV using Python

center_crop_scale.py

# Center Crop and Image Scaling functions in OpenCV
# Date: 11/10/2020
# Written by Nandan M

import cv2

def center_crop(img, dim):
	"""Returns center cropped image

	Args:
	img: image to be center cropped
	dim: dimensions (width, height) to be cropped
	"""
	width, height = img.shape[1], img.shape[0]

	# process crop width and height for max available dimension
	crop_width = dim[0] if dim[0]<img.shape[1] else img.shape[1]
	crop_height = dim[1] if dim[1]<img.shape[0] else img.shape[0] 
	mid_x, mid_y = int(width/2), int(height/2)
	cw2, ch2 = int(crop_width/2), int(crop_height/2) 
	crop_img = img[mid_y-ch2:mid_y+ch2, mid_x-cw2:mid_x+cw2]
	return crop_img

def scale_image(img, factor=1):
	"""Returns resize image by scale factor.
	This helps to retain resolution ratio while resizing.

	Args:
	img: image to be scaled
	factor: scale factor to resize
	"""
	return cv2.resize(img,(int(img.shape[1]*factor), int(img.shape[0]*factor)))


if __name__ == "__main__":
	image = cv2.imread('Kuvempu.jpg')

	ccrop_img = center_crop(image, (500,400))
	scale_img = scale_image(image, factor=1.5)

	cv2.imwrite("Kuvempu_center_crop.jpg", ccrop_img)
	cv2.imwrite("Kuvempu_scaled.jpg", scale_img)

how i can modify it for multiple pictures in a folder ?

use the following code inside the above script.

import os

# source images path to be cropped
PATH = "path/to/images"
img_list = os.listdir(PATH)

# create output folder to save new cropped images 
os.mkdir("output")

for img_f in img_list:
    if img_f.endswith("jpg"):
      img = cv2.imread(os.path.join(path,img_f))
      cropped_img = center_crop(img, (500,400))
      cv2.imwrite("output/image_center_crop.jpg", cropped_img)