diff --git a/floatimg.h b/floatimg.h
index 9a50ebc..126172f 100644
--- a/floatimg.h
+++ b/floatimg.h
@@ -73,6 +73,7 @@ double fimg_timer_get(int whot);
 /*	--> lib/contrast.c		*/
 int fimg_square_root(FloatImg *s, FloatImg *d, double maxval);
 int fimg_power_2(FloatImg *s, FloatImg *d, double maxval);
+int fimg_cos_01(FloatImg *s, FloatImg *d, double maxval);
 
 
 int fimg_mk_gray_from(FloatImg *src, FloatImg*dst, int k);
diff --git a/lib/Makefile b/lib/Makefile
index ac58414..ea2e3d4 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -2,7 +2,7 @@
 #	building the base library
 #
 
-COPT = -Wall -fpic -g -no-pie -DDEBUG_LEVEL=1
+COPT = -Wall -fpic -g -no-pie -DDEBUG_LEVEL=0
 OBJS = fimg-core.o fimg-pnm.o fimg-file.o fimg-math.o	\
 	fimg-timers.o operators.o fimg-2gray.o		\
 	interpolate.o fimg-compare.o contrast.o
diff --git a/lib/contrast.c b/lib/contrast.c
index 09dff29..377ae57 100644
--- a/lib/contrast.c
+++ b/lib/contrast.c
@@ -41,7 +41,7 @@ int		nbre, idx;
 double		dval;
 
 if (s->type != FIMG_TYPE_RGB) {
-	fprintf(stderr, "%s : type %d invalide\n",
+	fprintf(stderr, "%s : src type %d invalide\n",
 				__func__, s->type);
 	return -4;
 	}
@@ -49,6 +49,13 @@ if (s->type != FIMG_TYPE_RGB) {
 if (NULL==d) {
 	d = s;
 	}
+else	{
+	if (d->type != FIMG_TYPE_RGB) {
+		fprintf(stderr, "%s : dst type %d invalide\n",
+					__func__, s->type);
+		return -4;
+		}
+	}
 
 
 nbre = s->width * s->height * 3;
@@ -58,7 +65,42 @@ for (idx=0; idx<nbre; idx++) {
 	d->R[idx] = maxval * dval * dval;
 	}
 
-return -1;
+return 0;
 }
 
 /* ---------------------------------------------------------------- */
+/*
+		#macro Cos_01( X )
+		  (0.5-0.5*cos( 3.141592654 * X))
+		#end
+
+ */
+int fimg_cos_01(FloatImg *s, FloatImg *d, double maxval)
+{
+int		nbre, idx;
+double		dval;
+
+if (s->type != FIMG_TYPE_RGB) {
+	fprintf(stderr, "%s : type %d invalide\n",
+				__func__, s->type);
+	return -4;
+	}
+
+if (NULL==d) {
+	d = s;
+	}
+
+nbre = s->width * s->height * 3;
+
+for (idx=0; idx<nbre; idx++) {
+	dval = s->R[idx] / maxval;
+
+	d->R[idx] = maxval * (0.5 - 0.5 * cos(3.141592654*dval));
+	}
+
+return 0;
+}
+/* ---------------------------------------------------------------- */
+
+/* ---------------------------------------------------------------- */
+
diff --git a/lib/runme.sh b/lib/runme.sh
index 89144e7..f0bb3d9 100755
--- a/lib/runme.sh
+++ b/lib/runme.sh
@@ -1,11 +1,16 @@
 #!/bin/bash
 
+
+grabvidseq -s 960x720 -n 60 -p 0.5 -vv -o original.fimg
+
 make t && ./t
 
-for picz in src power2 squareroot
+for picz in original power2 squareroot cos_01
 do
 
-	../tools/fimgstats -v ${picz}.fimg
+	echo _______________ ${picz}
+
+	# ../tools/fimgstats -v ${picz}.fimg
 	../tools/fimg2pnm -v ${picz}.fimg ${picz}.pnm
 
 	convert -pointsize 36			\
@@ -13,7 +18,9 @@ do
 		-fill black -annotate +12+30 "${picz}" 			\
 		${picz}.pnm ${picz}.png
 
+	rm ${picz}.pnm
+
 done
 
-convert -delay 50 *.png foo.gif
+convert -delay 150 *.png foo.gif
 
diff --git a/lib/t.c b/lib/t.c
index 3558594..d5af635 100644
--- a/lib/t.c
+++ b/lib/t.c
@@ -75,23 +75,26 @@ FloatImg 	dessin, copy;
 double		maxi;
 
 foo = fimg_create_from_dump(fname, &dessin);
-
 foo = fimg_clone(&dessin, &copy, 0);
 
 
 maxi = (double)fimg_get_maxvalue(&dessin);
-fprintf(stderr, "avant  power_2  valeur maxi = %f\n", maxi);
+fprintf(stderr, "image source   valeur maxi = %f\n", maxi);
 
 fimg_power_2(&dessin, &copy, maxi);
-maxi = (double)fimg_get_maxvalue(&dessin);
+maxi = (double)fimg_get_maxvalue(&copy);
 fprintf(stderr, "apres  power_2  valeur maxi = %f\n", maxi);
 fimg_dump_to_file(&copy, "power2.fimg", 0);
 
 fimg_square_root(&dessin, &copy, maxi);
-maxi = (double)fimg_get_maxvalue(&dessin);
+maxi = (double)fimg_get_maxvalue(&copy);
 fprintf(stderr, "apres  square_root  valeur maxi = %f\n", maxi);
 fimg_dump_to_file(&copy, "squareroot.fimg", 0);
 
+fimg_cos_01(&dessin, &copy, maxi);
+maxi = (double)fimg_get_maxvalue(&copy);
+fprintf(stderr, "apres  cos 01       valeur maxi = %f\n", maxi);
+fimg_dump_to_file(&copy, "cos_01.fimg", 0);
 
 fimg_destroy(&dessin);
 
@@ -116,7 +119,7 @@ while ((opt = getopt(argc, argv, "gn:v")) != -1) {
 
 if (verbosity) fimg_print_version(0);
 
-foo = essai_contraste("src.fimg");
+foo = essai_contraste("original.fimg");
 fprintf(stderr, "retour essai contraste -> %d\n", foo);
 
 return 0;