Create duotone images with ImageMagick

duotone.sh

# Create Color Look Up Table
convert -size 1x1 xc:#008cff xc:#ffffff +append clut.gif

# Create gradient
convert -size 20x256 gradient: -rotate 90 clut.gif -interpolate bilinear -clut gradient.gif

# PNG to JPG
mogrify -format jpg *.png

# Convert to grayscale
mogrify -path grayscale -colorspace Gray *.jpg

# Create duotone images
for file in *.jpg; do convert $file clut.gif -interpolate bilinear -clut duotone/$file; done

# Resize
mogrify -path resized -resize 1920x1440\> *.jpg