cmon man this is not supposed to convert [Full Rip] [BMP] things. there are bunch of existing tools which supporting BMP to transparency PNG and you are using wrong one. girlcelly usually DOES include transparencies (confirmed this one does) so dont waste it . anyway thanks for sharing a lot.
note you can check a BMP file properties that says "bit depth" being 24-bit or 32-bit 24-bit BMP: colors only 32-bit BMP: enhanced format contains transparent for some reason most of image viewers ignore transparent in BMP then they both look the same. i know some people dont care about character standing images but this case is easy to fix... just pick another converter.