# Create a ZOOM-PAN effect using OpenCV and Python. Am image is read and the
# effect can be created either about the centre of the image or about any 
# specified point. This code is equivalent to FFmpeg commands for zoom-in and
# zoom-out effect described below. This effect is also called Ken Burns effect.

#Start with original dimension and zoom-in 0.0015 every iteration
#ffmpeg -loop 1 -i image.png -vf "zoompan=z='min(zoom+0.0015,1.5)':d=125" -c:v libx264 -t 5 -s "800x450" -y zoomedIn.mp4

#Start zoomed in at 1.5 and zoom out 0.0015 every iteration
#ffmpeg -loop 1 -i image.png -vf "zoompan= z='if(lte(zoom,1.0),1.5, max(1.001, zoom-0.0015))':d=125" -c:v libx264 -t 5 -s "800x450" -y zoomedout.mp4

import cv2

imgName = 'image.png'
vidName = "zoomedIn.mp4"
nfs = 20        #Number of Frames per Second, video duration = nframe/nfs
nframe = 100    #Total number of frames in the output vidoe
max_zoom = 2.0  #Maximum Zoom level (should be > 1.0)
max_rot = 30    #Maximum rotation in degrees, set '0' for no rotation

#Define the function for zooming effect
def zoomPan(img, zoom=1, angle=0, coord=None):
	cy, cx = [i/2 for i in img.shape[:-1]] if coord is None else coord[::-1]
	rot = cv2.getRotationMatrix2D((cx, cy), angle, zoom)
	res = cv2.warpAffine(img, rot, img.shape[1::-1], flags=cv2.INTER_LINEAR)
	return res

img = cv2.imread(imgName)
w = img.shape[1]
h = img.shape[0]
codec = cv2.VideoWriter_fourcc(*'mp4v')  #other formats can be DIVX or DIVD
video = cv2.VideoWriter(vidName, codec, nfs, (w, h))

#Make the loop for Zooming-in
i = 1
while i < nframe:
	zLvl = 1.0 + i / (1/(max_zoom-1)) / nframe
	angle = i * max_rot / nframe
	zoomedImg = zoomPan(img, zLvl, angle, coord=None)
	video.write(zoomedImg)
	i = i + 1

#Make the loop for Zooming-out to starting position
i = nframe
while i > 0:
	zLvl = 1.0 + i / (1/(max_zoom-1)) / nframe
	angle = i * max_rot / nframe
	zoomedImg = zoomPan(img, zLvl, angle, coord=None)
	video.write(zoomedImg)
	i = i - 1
	
video.release()