How does lanczo interpolation work

Also; does this help you:

raster - What is Lanczos resampling useful for in a spatial context? - Geographic Information Systems Stack Exchange

It focuses on GIS systems, but they have some interesting insights into the different resample methods:

They also have notes on Downsample in the link....

Well, I'm going to take a chance and give you some links to something that may help you; I found a VERY helpful document at frame.io

The Ultimate Guide to Premiere Pro's Render Quality Settings (frame.io)

There are some things within that document that I believe properly explain how resizing works; There is lots of useful info linked all over on the frame.io 'insider' site; Here is the text I thought may help you with your search:

You may have to layer some info from other sources to completly address your question, but I hope this elevates your knowledge in the areas of your interest.

What I found helpfull in this document was the explanations of 'max render' settings effects.....

I think the answer to your questions was the text that reads (to make it searchable).

"Lanczos 2 low-pass sampled with bicubic. Also described as modified bicubic with a scale-dependent pre-filter."

I hope this was helpfull....

the best way I can help ( cause I'm an idiot ) is to explain what the basics are... and how each digital iteration of doing it with computers is going to be different ( and a secret probably due to marketing and selling product ).

In the days of film ( before you were born probably ) a person could shoot with a 35mm camera ( using real plastic film ). Some people shot stuff that was gonna be made into national advertising BILLBOARDS along highway 66 and big cities and so on... by the person who hired the photographer.

Joel Meyerowitz used to shoot cigarette ads to make money and got hired by famous advertising companies to make it happen... cause Joel was fantastic and making young people have fun throwing fall leaves at each other in central park and having FUN !  But he shot with a 35mm leica and was really good at making young people ( models ) have fun !

So, eventually, that photo, along with text to make it plain to people that you were looking at what it's like to smoke some brand of cigarette, would end up in magazines and billboards all over the U.S.  and it paid his rent.

You probably see ads that say the same kind of thing even today. The geico ads with the cute salamander is a good example ??

Artists have to make money to survive and many of them do commercial work.

So, in film it was copy camera stuff using 35mm to shoot 4x5 negative ( enlarge it ). process it and shoot THAT, and make an 8x10 negative with copy camera. After THAT use giant projector to expose the PRINT to paste on billboard.

basically it is INCREMENTAL increases from the original to a product that looks OK. especially from a distance ( like a billboard, if you climb up there, will look a little blurry, but from a car on highway it looks pretty nice ).

that's what digital interolation does.... it use STEPS to gradually increase the SIZE of the original and intead of using optics ( copy cameras with film etc. ) it does it digitally sampling pixels and trying to reproduce them relative to other nearby pixels. This is tricky cause there is 4.2.0, 4.2.2, 4.4.4 and different bit depth ( 8 bit, 10 bit etc. ).

Now you know the basics... it's incrimental INCREASE of size of original in STEPS.