Preamble This is a companion thread to
(and inspired by the recent activity in my other thread concerning summed-area tables). I am fascinated by the low level stuff that goes on in image processing such as demosaicing that makes our favourite apps work so well.
One notable person in the resampling world is Robidoux (et al.). If you have heard of or are using LoHalo and NoHalo, which have been implemented in GIMP and other places, then you have had a taste of quality pixel wine. You can read an old article of his on the ImageMagick site: https://legacy.imagemagick.org/Usage/filter/nicolas/. It is old, so he doesn’t talk about LoHalo or NoHalo.
Some of you may have worked with him in the past or with LoHalo or NoHalo or other resampling filters. Would be nice to see a discussion here and perhaps have such filters be a part of G’MIC (or even have him join the conversation). If they are too complex or time consuming, perhaps we should start with finding parity with IM as I think we could benefit from these (and if not implementation, at least glean lessons from them):
For certain types of images and operations, tensor Lanczos is the default
-resizefilter and you can omit “
Robidoux is the default “
-distort Resize” filter. This is why the above command does not contain “
Mitchell is the default
-resizefilter for some types of images and operations. For this reason, “
-filter Mitchell” can often be omitted.
Not sure if G’MIC already has them. I don’t think so. All the filters mentioned in this post may have different, old and new versions depending on the library or source code. The disclaimer would be that I have no idea if anything requires permission to use. They certainly have licences attached to them. It is important to give credit where it is due.