This is a bit of Python code that uses PIL to slice very long images into segment sizes of your choice. For example take a 10,000px tall image, and slice it into 10 10,00px tall images.

slice_long_images.py

import Image
from __future__ import division
import math
import os

"""
This is a bit of Python code that uses PIL to slice very long images into segment sizes of your choice.
For example take a 10,000px tall image, and slice it into 10 10,00px tall images.

thanks to the great docs at http://www.packtpub.com/article/python-image-manipulation
"""


def enum(iterable, start = 1):
    """enumerate but with a starting position"""
    n = start
    for i in iterable:
        yield n, i
        n += 1

def long_slice(image_path, out_name, outdir, slice_size):
    """slice an image into parts slice_size tall"""
    img = Image.open(image_path)
    width, height = img.size

    upper = 0

    slices = int(math.ceil(height/slice_size))

    for i,slice in enum(range( slices )):
        left = 0
        upper = upper
        if i == slices:
            lower = height
        else:
            lower = int(i * slice_size)        
        bbox = (left, upper, width, lower)
        working_slice = img.crop(bbox)
        upper += slice_size
        working_slice.save(os.path.join(outdir, "slice_" + out_name + "_" + str(i)+".png"))

#use it like this
long_slice("variantCaller.png","tallcat", "/tmp", 1000)

whoops this is mine, I was anon by mistake