drifting_center_image_split.py

# small scrip to split pages when the desired midpoint drifts over the course of set of images
# requires imagemagick, specifically "convert" command

import os
import sys


def split_images(files, start_percentage, end_percentage, start_page, end_page):

	# determine percentage bump
	steps = len(files) - 1
	percentage_bump = float(end_percentage - start_percentage) / float(steps)
	print "incrementing each crop by %s" % percentage_bump

	# loop through files and fire
	for i,filename in enumerate(files):

		# DEBUG: range of pages to operate on
		if i >= start_page and i < end_page:
			print "splitting %s" % filename
			
			# determine offset
			if i == 0:
				percentage_offset = 0
			else:
				percentage_offset = float(i * percentage_bump)
			print "firing crop with percentage_offset %s" % percentage_offset

			# crop
			lcmd = 'convert %s' % filename + ' -gravity west -crop %s' % (start_percentage + percentage_offset) + 'x100%' + ' %s_0.jpg' % filename.split('.')[0]
			print lcmd
			os.system(lcmd)
			rcmd = 'convert %s' % filename + ' -gravity east -crop %s' % (100 - (start_percentage + percentage_offset)) + 'x100%' + ' %s_1.jpg' % filename.split('.')[0]
			print rcmd
			os.system(rcmd)


if __name__ == '__main__':
	images = [i for i in os.listdir('.') if i.endswith('.jpg')]
	'''
	expects arguments:
		- starting percentage
		- ending percentage
		- start page (counting from zero)
		- end page
	'''
	split_images(images, float(sys.argv[1]), float(sys.argv[2]), int(sys.argv[3]), int(sys.argv[4]))