Convert NScripter "bw2a" format JPGs to PNGs with ImageMagick

bw2a-to-png.ps1

# Converts all JPG files in the current directory from the "bw2a" format
# (the color on the left half of the image, and a mask for transparency
# on the right half) used by NScripter to PNG format with transparency.

gci . -Filter "*.jpg" |
Foreach-Object {
	# Split JPG into two halves:
	# - _temp-0.png is the color half
	# - _temp-1.png is the mask half
	magick $_ -crop 50%x100% _temp.png
	# Invert the mask half (since the format uses black for opaque but
	# imagemagick expects white)
	magick _temp-1.png -channel RGB -negate _temp-1-i.png
	# Grab the extensionless filename of the original JPG
	$arg_nameonly = (gi $_).Basename
	# Use the mask half to apply transparency to the color half
	magick composite -compose CopyOpacity _temp-1-i.png _temp-0.png "$arg_nameonly.png"
}