videopan.py

import subprocess as sp
import numpy as np
import signal
from PIL import Image

### TUKEY WINDOW
# https://leohart.wordpress.com/2006/01/29/hello-world/

def tukey_window(window_length, alpha=0.5):
    # Special cases
    if alpha <= 0:
        return np.ones(window_length) #rectangular window
    elif alpha >= 1:
        return np.hanning(window_length)

    # Normal case
    x = np.linspace(0, 1, window_length)
    w = np.ones(x.shape)

    # first condition 0 <= x < alpha/2
    first_condition = x<alpha/2
    w[first_condition] = 0.5 * (1 + np.cos(2*np.pi/alpha * (x[first_condition] - alpha/2) ))

    # second condition already taken care of

    # third condition 1 - alpha / 2 <= x <= 1
    third_condition = x>=(1 - alpha/2)
    w[third_condition] = 0.5 * (1 + np.cos(2*np.pi/alpha * (x[third_condition] - 1 + alpha/2))) 

    return w

### END TUKEY WINDOW

# using ffmpeg, slick
# from http://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/

FFMPEG_BIN = "ffmpeg"

command = [ FFMPEG_BIN,
            '-i', 'test.mov',
            '-f', 'image2pipe',
            '-pix_fmt', 'rgb24',
            '-vcodec', 'rawvideo', '-']

cmd = 'ffmpeg -i test.mov -f image2pipe -pix_fmt rgb24 -vcodec rawvideo -'
pipe = sp.Popen(cmd, shell=True, stdout=sp.PIPE, bufsize=10**8)

x_res = 1080
y_res = 1920

fps = 24
duration = 5
num_frames = 100

print "num frames?", num_frames
frames = []

while True:
  # x_res*y_res*3 bytes (= 1 frame)
  raw_image = pipe.stdout.read(x_res*y_res*3)
  if len(raw_image) < x_res*y_res*3:
    print "No data!"
    break
  # transform the byte read into a numpy array
  image = np.fromstring(raw_image, dtype='uint8')
  image = image.reshape((y_res,x_res,3)) # those dims always backwards, dunno why!
  # throw away the data in the pipe's buffer.
  frames.append(image)
  pipe.stdout.flush()

pipe.send_signal(signal.SIGINT)

print "got frames:", len(frames)

OVERLAP_FACTOR = 0.75
window_factor = 0.75
window_width = 128 # this is really what i'm going to be tuning, based on fps etc.
window_stride = int(window_width * (1-OVERLAP_FACTOR))

print "window width:", window_width
print "window stride:", window_stride

pano_width = len(frames)*window_stride
pano_img = Image.new("RGBA", (pano_width, y_res))

mask_array = np.ndarray(shape=(y_res, window_width), dtype="uint8")
tukey_template = tukey_window(window_width, window_factor) * 255

"""
import matplotlib.pyplot as plot
plot.plot(tukey_template)
axes = plot.gca()
margin = 10
axes.set_xlim([-margin,slice_x+margin])
axes.set_ylim([-margin,255+margin])
plot.show()
"""

for i in xrange(y_res):
  mask_array[i, :] = tukey_template

mask = Image.fromarray(mask_array, "L")

for i in xrange(len(frames)):
  begin_window_x = i*window_stride
  end_window_x = begin_window_x+window_width
  if end_window_x > pano_width:
    break
  frame_slice = Image.fromarray(frames[i][:,x_res/2-window_width/2:x_res/2+window_width/2,:])
  pano_img.paste(frame_slice, (i*window_stride, 0), mask=mask)

pano_img.save("test-pano.jpg")