BFFNT usage gives me the strange picture

[alicechan-dev]

When I was about to change the font file of Splatoon, using this script by the following command
python.exe -xf GambitMain.bffnt
It gives me no error, it worked fine, but the extracted sheets (images) are not okay.
It's almost pink-purple here. So is there a way to fix it?
GambitMain.zip

Using with pypng 0.0.19

[alicechan-dev]

In addition, the SwitchToolbox unlike this works fine, shows the font correctly I guess

[makungoron]

I guess I think it is because the original image is encoded by BC4_UNORM, and the glitched picture is the result of processing BC4_UNORM binaries as RGBA.

I faced a similar glitched picture when I was trying to export BotW font using bffnt.py.
BotW fonts were also encoded by BC4_UNORM.

[jgavrus]

@makungoron how did you fix it?