OpenCV Resize Image With Aspect Ratio The OpenCV resize() method, as the name suggests, resizes the image. import cv2 def resize (i , window_height = 500 ): aspect_ratio = float (i.shape[ 1 ]) / float (i.shape[ 0 ]) window_width = window_height/aspect_ratio i = cv2.resize(i , ( int (window_height) , int (window_width))) return i img = cv2.imread( 'image.jpg' ) img_resized = resize(img , window_height = 640 ) cv2.imshow( "ResizedImage" , img_resized) cv2.waitKey( 0 ) cv2.destroyAllWindows()