#!/usr/bin/python
# -*- coding: utf8 -*-
#
# Copyright (C) 2018 Niccolo Rigacci <niccolo@rigacci.org>
#
# Convert a portrait-oriented video to landscape mode. Crop a
# region from the original video and overlay it over a fake
# background. The background is created by blurring the cropped
# region and stretching it to the 16:9 aspect ratio.
#
# This program will generate a shell script, requiring the
# ffmpeg program and the convert tool from the ImageMagick.
# Tested with ffmpeg 3.4.2, ImageMagick 6.9.7.4 and Debian
# GNU/Linux 9 Stretch.

import os.path, random, sys

if len(sys.argv) < 2:
    print "Usage: %s video_file [crop_aspect] [offset_y]" % os.path.basename(sys.argv[0])
    sys.exit(1)

#--------------------------------------------------------------------------
# Input (source) video size. Width and height intended without rotation.
# Use the mediainfo tool to inspect the video file.
#--------------------------------------------------------------------------
video_in  = sys.argv[1]
input_w   = 1280
input_h   = 720
# Rotate 90 deg clockwise (1) or counterclockwise (2)
transpose = 1

# Region to crop from the input video:
#   0.000 = a square
#   0.885 = a rectangle occupying 1/3 of the final width
#   1.000 = the full (rotated) rectangle
if len(sys.argv) > 2:
    crop_aspect = float(sys.argv[2])
else:
    crop_aspect = 0.3

# Y offset of the cropped region (after the rotation):
#   0.0 = top
#   0.5 = center
#   1.0 = bottom
if len(sys.argv) > 3:
    offset_y = float(sys.argv[3])
else:
    offset_y = 0.5

# Overlay fuzzy border: percent of width (0% = no fuzzy):
fuzzy_border = 0.05

#--------------------------------------------------------------------------
# Output (destination) video size and filename.
#--------------------------------------------------------------------------
output_w = 1366
output_ratio_w = 16
output_ratio_h = 9
video_out = video_in[0:-4] + '.fixed.mp4'

#--------------------------------------------------------------------------
# End of customizable parameters, no changes required beyond this point.
#--------------------------------------------------------------------------

#--------------------------------------------------------------------------
# Temporary files: original video without rotation and overlay mask.
#--------------------------------------------------------------------------
rnd = random.randint(0, 9999)
tmp_norotate = 'tmp_norotate_%04d.mp4' % (rnd,)
tmp_mask = 'tmp_mask_%04d.png' % (rnd,)

#--------------------------------------------------------------------------
# Calculate the nearest even integer.
#--------------------------------------------------------------------------
def even_int(f):
    return int(round(f / 2.0)) * 2

#--------------------------------------------------------------------------
# Output (destination) video size.
#--------------------------------------------------------------------------
output_h = even_int(float(output_w) / float(output_ratio_w) * float(output_ratio_h))

#--------------------------------------------------------------------------
# Region to crop from the input video.
#--------------------------------------------------------------------------
crop_w = input_h
crop_h = even_int(input_h + float(input_w - input_h) * crop_aspect)

# Scale the cropped region to match the final video size.
scale_crop_w = even_int(float(crop_w) * float(output_h) / float(crop_h))
scale_crop_h = output_h

# Offset of the cropped region.
offset_crop_x = int(float(input_h - crop_w) / 2.0)
offset_crop_y = int(float(input_w - crop_h) * offset_y)

# X offset to overlay cropped region over the background.
offset_overlay_x = int(float(output_w - scale_crop_w) / 2.0)
offset_overlay_y = int(float(output_h - scale_crop_h) / 2.0)

# Calculate the cropping region and overlay offset.
crop     = 'crop=%d:%d:%d:%d' % (crop_w, crop_h, offset_crop_x, offset_crop_y)
overlay  = 'overlay=%d:%d' % (offset_overlay_x, offset_overlay_y)

# How much to blur the background.
avgblur  = int(float(output_w) / 25.0)

filter_crop = 'transpose=%d,%s,scale=%d:%d,setdar=%d/%d' % (transpose, crop, scale_crop_w, scale_crop_h, scale_crop_w, scale_crop_h)
filter_back = 'transpose=%d,%s,scale=%d:%d,setdar=%d/%d,avgblur=%d' % (transpose, crop, output_w, output_h, output_ratio_w, output_ratio_h, avgblur)

print "#!/bin/sh"
print '# Interpolate video "%s" to fix the aspect ratio.' % (video_in,)
print "# Input video size:  %dx%d (non rotated)" % (input_w, input_h)
print "# Cropping region:   %dx%d+%d+%d (rotated)" % (crop_w, crop_h, offset_crop_x, offset_crop_y)
print "# Output video size: %dx%d" % (output_w, output_h)

# Cannot remove the rotate metatag while applying transpose video filter.
# https://trac.ffmpeg.org/ticket/6370
ffmpeg = 'ffmpeg -i "%s" -c copy -metadata:s:v:0 rotate=0 %s' % (video_in, tmp_norotate)
print
print "# Make a copy of the input file removing rotate metadata."
print ffmpeg

# Create the mask (PNG image) to overlay with fuzzy borders.
fb = int(float(scale_crop_w) * fuzzy_border)
convert  = 'convert -size %dx%d' % (scale_crop_h, scale_crop_w)
convert += ' -define "gradient:bounding-box=%dx%d+0+0"' % (scale_crop_h, fb)
convert += ' -define "gradient:vector=0,%d,0,0" gradient:none-black' % (fb - 1)
convert += ' -define "gradient:bounding-box=%dx%d+0+%d"' % (scale_crop_h, scale_crop_w, scale_crop_w - fb)
convert += ' -define "gradient:vector=0,%d,0,%d" gradient:none-black' % (scale_crop_w - fb, scale_crop_w - 1)
convert += ' -composite -channel a -negate -rotate 90 %s' % (tmp_mask,)
print
print "# Make the overlay mask."
print convert

cfilter  = '[0:v]split [a][b];'
cfilter += '[a]%s [crop];' % (filter_crop,)
cfilter += '[b]%s [back];' % (filter_back,)
cfilter += '[1:v]alphaextract [mask];'
cfilter += '[crop][mask]alphamerge [masked];'
cfilter += '[back][masked]%s' % (overlay,)
ffmpeg = 'ffmpeg -i %s -loop 1 -i %s -filter_complex "%s" "%s"' % (tmp_norotate, tmp_mask, cfilter, video_out)
print
print "# Overlay the cropped region over the background to make the final video."
print ffmpeg

print
print "# Remove temporaty files."
print "rm %s %s" % (tmp_norotate, tmp_mask)