Author:

• Name: Yusuke Endoh
  Location: JP - Japan

To build:

    make

To use:

    ./prog < textfile > output.gif

Try:

To see the input files and feed them to the program, redirecting to GIF files:

    ./try.sh

Judges’ remarks:

To get the best experience, use a GIF viewer that can handle animated GIFs. With macOS you can use Safari using open -a Safari smily.gif.

Some things to consider are that this 2.5KiB gem encodes a 96 character 8x8 font (naively this could already take 6144 bytes) and a GIF encoder. But how does it know which characters are closed?

You should only give this program printable ASCII characters.

Unfortunately this won’t run on your PDP8, if you had one, as it needs at least 2MiB of memory to run in.

Author’s remarks:

This program generates an animated GIF from a plain text. Run:

    cc -o prog prog.c
    ./prog < invisible.txt > invisible.gif

Open invisible.gif with a GIF viewer that can show animated GIFs and then wait a minute. You will see a hidden message. Can you tell the difference between letters that leave the mark and ones that do not?

Other examples:

    ./prog < golem.txt > golem.gif
    ./prog < smily.txt > smily.gif

The program itself has a hidden message.

    ./prog < prog.c > prog.gif

Primary files

• prog.c - entry source code
• Makefile - entry Makefile
• prog.orig.c - original source code
• golem.txt - input data
• invisible.txt - input data
• smily.txt - input data
• try.sh - script to try entry

Secondary files

• 2018_endoh1.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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