diff --git a/lib/t.c b/lib/t.c
index 8197a87..72bf73a 100644
--- a/lib/t.c
+++ b/lib/t.c
@@ -53,7 +53,9 @@ return 0;
 int essai_interpolate(int k)
 {
 FloatImg	A, B, C;
-int		foo;
+int		foo, idx;
+char		ligne[200];
+float		fval;
 
 foo = fimg_create(&A, WI, HI, FIMG_TYPE_RGB);
 if (foo) {
@@ -75,14 +77,21 @@ if (foo) {
 	return foo;
 	}
 
-foo = fimg_interpolate(&A, &B, &C, 0.5);
-if (foo) {
-	fprintf(stderr, "%s err interpolate %d\n", __func__, foo);
-	return foo;
+#define NB	16
+for (idx=0; idx<NB; idx++) {
+	fval = (float)idx / (float)NB;
+	if (verbosity) fprintf(stderr, "%4d  %f\n", idx, fval);
+	foo = fimg_interpolate(&A, &B, &C, fval);
+	if (foo) {
+		fprintf(stderr, "%s err interpolate %d\n", __func__, foo);
+		return foo;
+		}
+	sprintf(ligne, "polate-%02d.pnm", idx);
+	foo = fimg_save_as_pnm(&C, ligne, 0);
 	}
-
-foo = fimg_save_as_pnm(&C, "interpolate.pnm", 0);
-
+/*
+ $ convert -delay 10 polate-* foo.gif ; animate foo.gif
+ */
 fimg_destroy(&A);	fimg_destroy(&B);	fimg_destroy(&C);
 
 return 0;
@@ -223,19 +232,23 @@ while ((opt = getopt(argc, argv, "gn:v")) != -1) {
 		case 'g':	gray++;			break;
 		case 'n':	foo=atoi(optarg);	break;
 		case 'v':	verbosity++;		break;
+		default:
+			fprintf(stderr, "%s: oh, %c is a bad opt.\n",
+						argv[0], opt);
+			exit(5);
 		}
 	}
 
 if (verbosity) fimg_print_version(0);
 
-foo = essai_normalize();
-fprintf(stderr, "retour essai normalize -> %d\n", foo);
+// foo = essai_normalize();
+// fprintf(stderr, "retour essai normalize -> %d\n", foo);
 
-foo = essai_contraste("quux.fimg");
-fprintf(stderr, "retour essai contraste -> %d\n", foo);
+// foo = essai_contraste("quux.fimg");
+// fprintf(stderr, "retour essai contraste -> %d\n", foo);
 
-foo = essai_clone_et_copy(0);
-fprintf(stderr, "retour essai clone'n'copy -> %d\n", foo);
+// foo = essai_clone_et_copy(0);
+// fprintf(stderr, "retour essai clone'n'copy -> %d\n", foo);
 
 foo = essai_interpolate(0);
 fprintf(stderr, "retour essai interpolate -> %d\n", foo);
diff --git a/tools/fimgops.c b/tools/fimgops.c
index d79542a..e536342 100644
--- a/tools/fimgops.c
+++ b/tools/fimgops.c
@@ -84,7 +84,7 @@ switch (action)	{
 	case OP_SUB:
 		foo = fimg_sub_3(A, B, D);		break;
 	case OP_MIX:
-		if (verbosity) fprintf(stderr, "%s: fvalue is %f\n",
+		if (verbosity) fprintf(stderr, "%s:mix: fvalue is %f\n",
 						__func__, global_fvalue);
 		foo = fimg_interpolate(A, B, D, global_fvalue);
 		break;