Replacing the shutdown screen

The UL warning image displayed during shutdown can be modified by replacing the file

/usr/share/boot-anim/ul_warning.565

with an appropriate alternative, in 1200x900 "565" format.

For example, you might wish to try: modified-shutdown.565.

Note that 565-format images seem very large, but we use a compressing filesystem which slims them down nicely.

On a linux system, you can convert 1200x900 PNG images to 565-format images as follows:

$ pngtopnm myfile.png | ./ppmto565.py > myfile.565

using the following python script named 'ppmto565.py':

#!/usr/bin/python2.5
"""Convert PPM-format images to 565-format."""
from __future__ import division, with_statement
import sys

def eat_comment(inf): # just read #, read until next EOL
    while True:
        c = inf.read(1)
        if c == '\n' or c == '\r': break # read to EOL
    return c

def read_token(inf):
    # eat up leading whitespace
    while True:
        c = inf.read(1)
        if c == '#': eat_comment(inf)
        elif not c.isspace(): break
    # now read in non-whitespace.
    s = c
    while True:
        c = inf.read(1)
        if c == '#': c = eat_comment(inf)
        if c.isspace(): break
        s += c
    # done!
    return s

def main(inf, outf):
    import struct
    # read ppm from input
    magic = inf.read(2)
    assert magic == 'P6'
    width = int(read_token(inf))
    height = int(read_token(inf))
    maxval = int(read_token(inf))
    unpackstr = '!3B' if maxval < 256 else '!3H'
    unpacklen = struct.calcsize(unpackstr)
    # write header
    outf.write(struct.pack('@IIP', width, height, 0))
    # read pixel data, convert, and write it to output
    def scale(x, y): return int((y*x/maxval)+0.5)
    for y in xrange(0, height):
        for x in xrange(0, width):
            red, green, blue = struct.unpack(unpackstr, inf.read(unpacklen))
            encoded = (scale(red, 0x1f) << 11) + \
                      (scale(green, 0x3f) << 5) + \
                      (scale(blue, 0x1f))
            outf.write(struct.pack('@H', encoded))

if __name__ == '__main__':
    import sys
    main(sys.stdin, sys.stdout)