From 130f83a27f2a9dc8a15fc8908f15227817f8805e Mon Sep 17 00:00:00 2001
From: Jens Ahrensfeld <jens@jayfield.org>
Date: Wed, 7 Oct 2020 19:50:13 +0000
Subject: [PATCH] - improved clipping - matte is clipped matte white

git-svn-id: http://moon:8086/svn/matlab/trunk@150 801c6759-fa7c-4059-a304-17956f83a07c
---
 chromakey/chromakey.m  | 11 ++++++-----
 chromakey/clip_black.m |  4 +---
 chromakey/clip_white.m |  5 +----
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/chromakey/chromakey.m b/chromakey/chromakey.m
index 0f11b3e..f1e12e5 100644
--- a/chromakey/chromakey.m
+++ b/chromakey/chromakey.m
@@ -29,11 +29,11 @@
 function chromakey (prj_name, k_e_matte, k_e_edge)
 
 k_ds_matte = 1.0;
-clip_white_thresh = 0.80;
-clip_white_amp = 3;
+clip_white_thresh = 0.60;
+clip_white_amp = 5;
 
-clip_black_thresh = 0.20;
-clip_black_amp = 3;
+clip_black_thresh = 0.40;
+clip_black_amp = 5;
 
 [im_rgb, ref_rgb] = prj_load(prj_name);
 
@@ -47,7 +47,8 @@ figure;
 imshow(conf); title("conf")
 
 matte_clipped_w = clip_white(matte, clip_white_thresh, clip_white_amp);
-matte_clipped_b = clip_black(matte, clip_black_thresh, clip_black_amp);
+matte_clipped_b = clip_black(matte_clipped_w, clip_black_thresh, clip_black_amp);
+matte = matte_clipped_w;
 
 figure;
 imshow(matte_clipped_w.*matte_clipped_b); title("matte_{clipped}")
diff --git a/chromakey/clip_black.m b/chromakey/clip_black.m
index e4c9f07..8a51387 100644
--- a/chromakey/clip_black.m
+++ b/chromakey/clip_black.m
@@ -24,9 +24,7 @@
 ## Created: 2020-10-04
 
 function y = clip_black (x, thresh, k)
-ind = find (x >= thresh);
 
-y = x/k;
-y(ind) = thresh/k + (x(ind)-thresh)*(1+thresh);
+y = 1 - min(1, exp(-k*max(0,((1-thresh)-(1-x)))));
 
 endfunction
diff --git a/chromakey/clip_white.m b/chromakey/clip_white.m
index a186fcd..6ed26f0 100644
--- a/chromakey/clip_white.m
+++ b/chromakey/clip_white.m
@@ -25,9 +25,6 @@
 
 function y = clip_white (x, thresh, k)
 
-ind = find (x >= thresh);
-
-y = x;
-y(ind) = thresh + (x(ind)-thresh)*k;
+y = min(1, exp(-k*max(0,(thresh-x))) - exp(-k*thresh));
 
 endfunction