Landon Curt Noll
4ee4c731f7
While not strictly necessary, replacing the two ASCII tab characters in the markdown copyright comment makes it easier to detect problematic TAB indentation within markdown files. After this commit, only 90 markdown files have leading ASCII TAB characters. And again, while not strictly necessary, we can consider running expand on those 90 markdown files to see what effect that might have on the HTML files they produce. Replace leading ASCII TAB characters with multiples of 8 ASCII SPACE characters (the default action of the `expand(1)` tool) might have an negative effect on some HTML formatting where **hack-a-round** formatting was attempted to fix broken indentation caused by problematic ASCII TAB characters. Think of this as a baseline for evaluating leading TAB characters within markdown files. TODO: Consider either using `expand(1)` to replace leading ASCII TAB characters with multiples of 8 ASCII SPACE characters AND/OR modifying the appropriate `bin` tool to convert leading ASCII TAB characters into multiples of 8 ASCII SPACE characters.
143 lines
4.2 KiB
Markdown
143 lines
4.2 KiB
Markdown
## To build:
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``` <!---sh-->
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make
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```
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## To use:
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``` <!---sh-->
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./akari [ input_file | - ] [ output_file | - ] [even]
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```
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## Try:
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``` <!---sh-->
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./try.sh
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```
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## Judges' remarks:
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`Akari` is an image downsampling utility that accepts 3 input formats:
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* [PGM](https://netpbm.sourceforge.net/doc/pgm.html)
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([netpbm](https://netpbm.sourceforge.net/doc/) [greyscale
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image](https://en.wikipedia.org/wiki/Grayscale). `Akari` only accepts `PGM`
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files with the header: `P5 <width> <height> 255`. Images with extra comments
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_such as the ones produced by [GIMP](https://www.gimp.org) will **not be parsed
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properly**_.
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* [PPM](https://netpbm.sourceforge.net/doc/ppm.html) (netpbm RGB image). Only
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`PPM` files with the header `P6 <width> <height> 255` are accepted.
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* [ASCII art](https://en.wikipedia.org/wiki/ASCII_art) (with [end of
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lines](https://en.wikipedia.org/wiki/Newline) in LF bytes only, _**not** CR-LF_!)
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Anything that is not parsable as `PGM` or `PPM` will be downsampled as ASCII art.
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## Author's remarks:
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`Akari` is an image downsampling utility. She accepts up to 3 arguments:
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The first argument is the input image. If it's `-` or unspecified, `Akari`
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will read from `stdin`.
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The second argument is the output image. If it's `-` or unspecified,
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`Akari` will write to `stdout`.
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The third argument, if specified, causes `Akari` to keep even pixels on even
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[scanlines](https://en.wikipedia.org/wiki/Scan_line). By default `Akari` will
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keep odd pixels on odd [scanlines](https://en.wikipedia.org/wiki/Scan_line).
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### Examples:
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``` <!---sh-->
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gcc akari.c -o akari
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./akari < example.ppm > odd_output.ppm
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./akari - - even < example.ppm > even_output.ppm
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./akari example.ppm odd_output.ppm
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```
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`Akari` accepts 3 input formats:
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* [PGM](https://netpbm.sourceforge.net/doc/pgm.html)
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([netpbm](https://netpbm.sourceforge.net/doc/) [greyscale
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image](https://en.wikipedia.org/wiki/Grayscale). `Akari` only accepts `PGM`
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files with the header: `P5 <width> <height> 255`. Images with extra comments
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such as the ones produced by [GIMP](https://www.gimp.org) will not be parsed
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properly.
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[PPM](https://netpbm.sourceforge.net/doc/ppm.html) (netpbm RGB image). Only
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`PPM` files with the header `P6 <width> <height> 255` are accepted.
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* ASCII art (with end of lines in LF bytes only, not CR-LF)
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This is useful for decoding some curiously interlaced images, such as
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the included [example.ppm](example.ppm).
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Anything that is not parsable as `PGM` or `PPM` will be downsampled as
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ASCII art. Since the source code is formatted as ASCII art, it's only
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natural to try:
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``` <!---sh-->
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./akari akari.c akari2.c
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```
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`akari2.c` is also a valid C program, and accepts up to 1 argument.
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By default, this second program reads text from `stdin` and writes
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expanded output to `stdout`. If the extra argument is specified, the
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output text will also pass through a rot13 filter.
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``` <!---sh-->
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gcc akari2.c -o akari2
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./akari2 < input.txt > expanded_output.txt
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./akari2 rot13 < input.txt > expanded_and_rot13_output.txt
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```
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You can combine the two programs together to have just a regular rot13
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filter:
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``` <!---sh-->
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./akari2 rot13 < input.txt | ./akari > rot13.txt
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```
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Of course, we wouldn't stop with just 2 programs, you can downsample
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the source *again* and get yet another C program:
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``` <!---sh-->
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./akari < akari.c | ./akari > akari3.c
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```
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We must go deeper:
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``` <!---sh-->
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./akari < akari.c | ./akari | ./akari > akari4.c
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```
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`akari3.c` and `akari4.c` are still (mostly valid) C programs.
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`gcc -Wall` will output a few warnings, but still produce output
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executables. The output executables each print a message to `stdout`.
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It takes quite a bit of skill and obfuscation to interleave a
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C program 4 levels deep, it's much easier to interleave something like
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a `brainf#$%` program in a C program, for example. For comparison, a
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`brainf#$%` program is embedded inside [akari.c](%%REPO_URL%%/2011/akari/akari.c).
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<!--
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Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
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You are free to share and adapt this file under the terms of this license:
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Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
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For more information, see:
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https://creativecommons.org/licenses/by-sa/4.0/
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-->
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