I love this comic, because I've been tuning my JPEG encoder especially to avoid XKCD-destroying artefacts!
(both files are at incredibly low quality setting to exaggerate the effect)
Now, if only I could convince everyone to use a better JPEG encoder... I've created an online UI for it, so you don't have to compile/install anything.
How did you add that image? Silly DN won't let me add one via markdown.
ah, had to refresh the page after posting to see the image. weird.
I assume this is built into ImageOptim?
Yes, if you enable Lossy in preferences.
The "9GAG" watermark really does it for me.