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diff --git a/chromakey/alpha.png b/chromakey/alpha.png
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diff --git a/chromakey/background.png b/chromakey/background.png
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diff --git a/chromakey/bluescreen.m b/chromakey/bluescreen.m
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+## Copyright (C) 2020 Jens
+## 
+## This program is free software: you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+## 
+## This program is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+## 
+## You should have received a copy of the GNU General Public License
+## along with this program.  If not, see
+## <https://www.gnu.org/licenses/>.
+
+## -*- texinfo -*- 
+## @deftypefn {} {@var{retval} =} bluescreen (@var{input1}, @var{input2})
+##
+## @seealso{}
+## @end deftypefn
+
+## Author: Jens <jens@orion>
+## Created: 2020-10-03
+
+function retval = bluescreen (img_name, k_ds, k_gain)
+im = im2double(imread(img_name));
+im_rgb = imresize(im, 2);
+se = strel('square',3)
+
+ref_rgb = toRef([0 0.5 1], size(im_rgb));
+
+close all;
+
+figure;
+imshow(ref_rgb);
+
+figure;
+despilled_rgb = im_rgb - k_ds*ref_rgb;
+imshow(despilled_rgb);
+
+figure;
+mask = min(1, k_gain*similarity(rgb2hsv(despilled_rgb), rgb2hsv(ref_rgb)));
+imshow(mask);
+
+figure;
+final = despilled_rgb.*mask;
+imshow(final);
+
+imwrite(final, 'final.png','png','alpha', mask);
+imwrite(mask, 'alpha.png','png');
+
+retval = 0;
+
+function r = toRef(ref, d)
+	r = repmat(reshape(ref,1, 1, 3), d(1), d(2));
+endfunction
+
+function s = similarity(im, ref)
+	s = abs(im(:,:,1) - ref(:,:,1));
+endfunction
+
+endfunction
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