Created
July 21, 2010 16:26
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| #!/usr/bin/env ruby | |
| # Test script for yet another JPEG glitch technique. | |
| # Rewrite YCbCr sampling factors in JPEG header. | |
| # It's a version of http://gist.github.com/167060 | |
| require 'erb' | |
| data = File.open(ARGV.first) {|f| f.read } | |
| data.force_encoding Encoding::BINARY | |
| sof0 = data.index "\xFF\xC0" | |
| ns = data[sof0 + 9].unpack('C').first | |
| files = (4 ** ns).times.collect do |i| | |
| sign = "%0#{2*ns}b" % i | |
| ns.times do |j| | |
| flag1 = (sign[j * 2] == "1") ? 0x20 : 0x10 | |
| flag2 = (sign[j * 2 + 1] == "1") ? 0x02 : 0x01 | |
| data[sof0 + 11 + j * 3] = [flag1 | flag2].pack('C') | |
| end | |
| file = sign + '.jpg' | |
| File.open(file, 'w') do |f| | |
| f.print data | |
| end | |
| file | |
| end | |
| file = 'index.html' | |
| File.open(file, 'w') do |f| | |
| f.print ERB.new(DATA.read).result(binding) | |
| end | |
| #`open index.html` | |
| __END__ | |
| <html> | |
| <head><title>Rewrite SOF0 Glitch</title></head> | |
| <body> | |
| <% files.each do |i| %> | |
| <img alt="<%= i %>" src="<%= i %>"> | |
| <% end %> | |
| </body> | |
| </html> |
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