Remove Color Cast on Negatives

README.md

Takes an input Tiff of a color negative, and subtracts the film backing color contamination per http://www.dpreview.com/forums/post/499854

Requires Image Magick with libtiff. Easy way to get that on OSX is with homebrew. Just run

brew install --with-libtiff imagemagick

with brew installed. Then you use the script like

./remove_color_cast filename.tif

Easy peasy. To do a batch of tifs you'd do something like the following.

mkdir out
for i in *.tif; do remove_color_cast $i && mv out.tif out/$i; done

example.png

remove_color_cast.sh

#!/bin/bash

if [ $# -eq 0 ]
  then
    echo "No arguments supplied"
else
	convert $1 -set colorspace CMY -separate %d.tif
	convert -page +0+0 0.tif -alpha on -channel a -evaluate set 20% -background black -layers flatten YELLOW.tif 
	convert -page +0+0 1.tif -alpha on -channel a -evaluate set 40% -background black -layers flatten RED.tif 
	composite 2.tif -compose plus YELLOW.tif 2.tif
	composite 2.tif -compose plus RED.tif 2.tif
	composite 1.tif -compose plus RED.tif 1.tif
	convert 0.tif 1.tif 2.tif -set colorspace CMY -combine -set colorspace sRGB out.tif
	convert out.tif -negate out.tif
	rm YELLOW.tif RED.tif 0.tif 1.tif 2.tif
fi