OS
Win10x64

Irfanview 64 v 4.54


This does not work. File is converted to bpp=4, not bpp=1. Same result if batching multiple files.
"c:\program files\irfanview\i_view64.exe" e:\beers1\0020.jpg /bpp=1 /convert=e:\beers2\0020a.jpg

This works, if opening but not converting file. File opens as bpp=1.
"c:\program files\irfanview\i_view64.exe" e:\beers1\0020.jpg /bpp=1