Hello all
As you probably know I am always looking for solutions to scan negative
films either in super 8 or in 16mm.
So my main problem is to convert a C41 film colors to reversal and it's
not as simple as just inverting, far from it.
The orange bias must removed first (RGBs are 235,172,121).
However I came across this neat script that is using image magick (see
below)
It works wonders ... on still frames.
Film being film, e.g a succession of scanned tiff files, there is always
a bit of dust or something to spoil the process and make colors of a
specific scene behaving like a firework.
A bit like setting the histogram on automatic and expecting it to give
a constant result over one particular scene. It may work on video, not
on films.
Anyway, what I am looking for is a developper that could make a plugin
(as in video effect) based on the script below that could find some
correcting values and set them constant for a given length of time. A
bit like the histogram : set on automatic for a first quick correction,
remove automatic, manual better adjustement if needed, next set of frames.
Interest for the cinelerra community : film users as I usually don't
have a choice for this purpose: they need to go Windows or Mac and
having this option could attract more users (and developers).
For say the script with image magick is dead slow, 1 fps or someting on
16 bits 1600x1200 pixels.
I know that money can be an issue, but I am quite happy to pay for it
and get someone to incorporate it in the source for everybody to enjoy it.
Anyhow, here is the script, nothing complex as far as I can understand
but to get that into cinelerra is out of my reach.
Hope this could trigger some attention because a lot of people are still
shooting 16mm and S8 in neg. Not a media to bury yet.
Best
Edouard
#!/bin/bash
# negfix7 ver 1.0
# GNU General Public License v2
# (C) 2009 JaZ99 - http://www.flickr.com/photos/jaz99/
# This little script converts C-41 negative (scanned as 3*16-bit _linear_
# positive) into the posivite image. Output image might require some
# minor tweaking (gamma, contrast, exposition, etc.).
# Reguires ImageMagick Q16 version (http://www.imagemagick.org/).
# USAGE: negfix7 input_file [output_file]
# IMPORTANT: Scanned image MUST contain some orange mask
# and MUST NOT contain holder fragments!
F="${1}"
OUTF=P_`basename "$1"`
OUTF="${2:-$OUTF}"
margin=0.96
# Let's get some statistics first....
eval set -- `convert "${F}[0]" -strip -blur 7x7 -format \
"%[fx: minima.r*$margin] "\
"%[fx: minima.g*$margin] "\
"%[fx: minima.b*$margin] "\
"%[fx: log(minima.r/maxima.r)/log(1/(256*maxima.b))] "\
"%[fx: log(minima.g/maxima.g)/log(1/(256*maxima.b))] "\
"%[fx: log(minima.b/maxima.b)/log(1/(256*maxima.b))] " info:`
echo $F: $*
echo -n "Writing $OUTF... "
convert -shave 2x2 "${F}[0]" -strip -colorspace RGB \
-channel R -fx "$1/u" -gamma $4 \
-channel G -fx "$2/u" -gamma $5 \
-channel B -fx "$3/u" -gamma $6 \
-channel RGB "$OUTF"
echo "Done."
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