Bmap image resizing algorithm

[Fironet]

Years go I used a very obscure image viewer named Bmap that had a superb scaling algorithm when resizing windows smaller and I've always wondered what it used to achieve this as the image quality remained crystal clear without adding a sharpness filter per se.

Example comparisons (Bmap left, Pictus right):

source image - 1
source image - 2

All I know is it used Freeimage v3.6.1, according the About window, and the source code for the program was released. Any thoughts what it may have used? Would be a great fit for Pictus.

[poppeman]

Bmap seems to offload the resampling on Windows, which complicates things a bit. How does Lanczos3 compare?

[Fironet]

How does Lanczos3 compare?

That's Lanczos3 in the Pictus screenshots above. So, not as sharply though it does produce smooth blends. Haven't actually found any other image viewers that uses the same scaling as Bmap that I've tested, or at least not with the settings it uses.

[poppeman]

Ah, alright. Figuring out exactly what algorithm windows is using is probably a bit hard, but it should be possible to add a less soft algorithm like bicubic.