Detect Moire Filter


#1

I’ve just added a “Detect Moire” filter to Testing -> Iain Fergusson.

It’s a problem I’ve been trying to solve for a while and I was inspired to revisit it by the recent work done to combine demosaicers in Raw Therapee.

It’s pretty good at detecting moire on low ISO images, high ISO images require a bit of fiddling to make sure noise is not causing false positives.


#2

Interesting. Can you explain the algorithmsin layman’s terms?


#3

It looks for small (pixel level) high contrast details and also looks for edges. Moire is likely to occur in the areas that have small high contrast details that aren’t edges.

Edit: And if there are a lot of those feature in one area it is probably moire.


#4

And if there are a lot of those feature in one area it is probably moire.

Or cloth?


#5

Yes. That’s why detecting moire is tricky. You have to be precise in what you determine to be high contrast details and what is an edge. For example, I use a method for detecting details that is biased towards differences along diagonals.