Takes a directory of screenshots taken by Luma 3DS (v9.0+) and stitches them together.

mergeluma.py

"""Luma3DS (v9.0+) screenshots are dumped into two seperate files (_top and _bot) and stored
in .bmp format.  This script lets you merge those files into one (as a .png) fairly quickly.
A caveat:
- This script is not clever and will not protect you from yourself.  It pretty much expects
  these files to be exactly 400x240 and 320x240 BMPs in RGB format.  Anything else will
  probably crash it.
Some good news though, this process takes a little over a minute for 140 odd screenshots, so
you won't be waiting long for your output.  Also my one test run took my storage from 70 megs
to a little over 20, so that's a nice benefit.
"""

from PIL import Image
from glob import glob

def merge_files(top, bot):
    """Merges the provided *_top.bmp and *_bot.bmp files created by
    NTR's screenshot function into a single .png file.  As the top screen
    of the 3DS is slightly wider than the bottom, the bottom screen will
    be centered and have transparent gutters to the left and right.
    
    top = 400x240
    bot = 320x240"""

    # create a new output image
    output = Image.new(mode='RGBA', size=(400,480), color=(0, 0, 0, 0))

    # open the specified image files
    t = Image.open(top)
    b = Image.open(bot)

    # paste the input into the output
    output.paste(t, box=(0,0))
    output.paste(b, box=(40,240))

    # save her to disk
    fn = top.replace('_top.bmp','.png')
    output.save(fn, 'png')
    
    # close our files
    t.close()
    b.close()
    output.close()


if __name__ == '__main__':
    files = glob('*_top.bmp')
    for x in files:
        y = x.replace('top.bmp', 'bot.bmp')
        print('merging %s and %s' % (x, y))
        merge_files(x, y)