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@Neurogami

Neurogami/glitch.rb

Created Aug 12, 2013
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What would you like to do?
Simple script to rin perfectly good image files.
#!/usr/bin/env ruby
=begin
Simple script to smack your glitch up.
Call this program with the name of an image file, and two numbers
The first number is used to determine when to mess with a byte in the
image file. If you pass in, say 2000, then even 2000th byte gets tweaked.
The second number is a bit-mask value. Keep it under 255. It's used to set some
bits in any tweaked byte.
The output file name is derived from the input file name and the two integers you give.
It makes it easier to see to what parameters gave what results.
=end
if ARGV.size < 3
puts "Usage: #{__FILE__} source-image byte-mod-int bitmask-int"
exit
end
infile = ARGV.shift
byte_mod = ARGV.shift.to_i
bitmask = ARGV.shift.to_i
ext = File.extname infile
base = infile.sub /#{ext}$/, ''
outfile = "#{base}.#{byte_mod}-#{bitmask}#{ext}"
warn "Glitch #{infile} and write to #{outfile}"
b_counter = 0
File.open(infile, 'rb') do |f|
File.open(outfile, "w+b") do |ff|
f.each_byte do |b|
b_counter += 1
b_counter %= byte_mod
if b_counter == 0
b = b && bitmask
end
# The trick here is that 'print'
# works with strings and will bork your
# data in the wrong way, hence `chr`
ff.print b.chr
end
end
end
=begin
Copyright (c) 2013 James Britt / Neurogami
Released under the The MIT License - http://opensource.org/licenses/MIT
Feed your head
Hack your world
Live curious
=end
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