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Comment by TGower | Hacker News Reader

"elected for no obvious reason" isn't quite right, as a test image for computer graphics it has regions of very high frequency detail and regions of very low frequency detail which make it easier to spot various compression artifacts, and it makes a good study for edge detection, with both very clear edges along the outline, but more subjective edges in the feathering.

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It's redish. Ok it has a blur and details on the foreground but could have been any image with blurred background and a face.

"very low frequency detail", we are talking about a 512x512 picture here, it has low and high frequency details (FFT speaking) like most photos.

"Good for edges detection" doesn't mean anything. Like, is the image good for edge detection or the algorithm is good at detecting edges ? What does "subjective edges" even mean ? Does it mean hard to spot ?

That looks like technical reasons but it just noise. They literally grab a playboy magazine and decided it was well enough (and indeed, it wasn't that bad, yes). Still not professional. The message is "We have playboy magazines at work and we are proud of it".

Try out running different edge detection algorithms on that image and you will see that there is a lot of disagreement amongst them in the feathering region. Exploring what the differences are, and how the algorithms lead to those differences helps build intuition about the range of things we might call an "edge", and which algorithm is appropriate for a particular task at hand.

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