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Matts (1087)

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I work for MessageLabs [] in Toronto, ON, Canada. I write spam filters, MTA software, high performance network software, string matching algorithms, and other cool stuff mostly in Perl and C.

Journal of Matts (1087)

Friday July 15, 2005
12:20 PM

Lossy or lossless

[ #25729 ]

Found a great page on lossy vs lossless compression, testing the user to see if you can tell the difference. Try the test and let me know how you did.

I got 7 out of 10.

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  • at least not for some offices.
    # I had a sig when sigs were cool
    use Sig;
  • I started badly but quickly reaslised that it's easy to spot a JPEG if there is gradual colour JPEGs look more blotchy. So the ones with the grey backgrounds turned out to be dead easy, those with solid backs were much harder to discriminate.

    -- "It's not magic, it's work..."
  • I found the "quality 11" ones to be very difficult, having to go on the subtle gradient splotchiness that ajt mentioned. The "quality 7" ones typically had serious edge color distortion.
  • Not sure how I did so well. My crummy 1028x768 laptop lcd was a heck of a handicap. I mostly used shadows to figure it out. For some reason I had an easier time if there was some red in the image.

    Interesting test.
  • I got nine out of ten. But I'm a really picky bastard. My wife is a graphic designer, but she asks me to proof stuff when she wants to know if there's too much dot gain or if an image is misplaced by .1 pica.

  • I was able to spot a few artifacts near heads and shoulders, and once in the shadows, but on my laptop, the best I could do was 5.