diff --git a/Fonderie/crapulator.c b/Fonderie/crapulator.c
index 423c7602..2ac41bbb 100644
--- a/Fonderie/crapulator.c
+++ b/Fonderie/crapulator.c
@@ -123,7 +123,7 @@ switch (idFx) {
 		retval = trinarize(image, 0);
 		break;
 	case 24:			/* experiment ! */
-		retval = des_bords_sombres_a(image, 260);
+		retval = des_bords_sombres_a(image, 160);
 		break;
 	case 25:
 		/* please make this function more tweakable */
diff --git a/Fonderie/sfx.c b/Fonderie/sfx.c
index c603d293..90e8a7c9 100644
--- a/Fonderie/sfx.c
+++ b/Fonderie/sfx.c
@@ -23,27 +23,29 @@ extern	int		verbosity;
 int des_bords_sombres_a(FloatImg *pimg, int offset)
 {
 float		coef;
-int		xpos, lidx, y;
+int		xpos, xp2, lidx, y;
 
 #if DEBUG_LEVEL
 fprintf(stderr, ">>> %s ( %p %d )\n", __func__, pimg, offset);
 #endif
 
-if (offset<0 || offset>pimg->width) {
+if (offset<0 || offset>=pimg->width) {
 	fprintf(stderr, "%s offset %d is bad\n", __func__, offset);
 	return -66;
 	}
 
 for (y=0; y<pimg->height; y++) {
-	lidx = y * pimg->width;
+	lidx = y * pimg->width;			/* start of the
+						   'y' line */
 	for (xpos=0; xpos<offset; xpos++) {
 		coef = (float)xpos / (float)offset;
 		pimg->R[xpos+lidx] *= coef;
 		pimg->G[xpos+lidx] *= coef;
 		pimg->B[xpos+lidx] *= coef;
-		pimg->R[(pimg->width-xpos)+lidx] *= coef;
-		pimg->G[(pimg->width-xpos)+lidx] *= coef;
-		pimg->B[(pimg->width-xpos)+lidx] *= coef;
+		xp2 = pimg->width-xpos;
+		pimg->R[xp2+lidx] *= coef;
+		pimg->G[xp2+lidx] *= coef;
+		pimg->B[xp2+lidx] *= coef;
 		}
 	}
 
@@ -52,6 +54,28 @@ return 0;
 /* -------------------------------------------------------------- */
 int trinarize(FloatImg *pimg, int notused)
 {
+float		mm[6], mRa, mGa, mBa, mRb, mGb, mBb;
+int		foo, size;
+
+#if DEBUG_LEVEL
+fprintf(stderr, ">>> %s ( %p %d )\n", __func__, pimg, notused);
+#endif
+
+foo = fimg_get_minmax_rgb(pimg, mm);
+mRa = (mm[1] - mm[0]) * 0.33333;
+mGa = (mm[3] - mm[2]) * 0.33333;
+mBa = (mm[5] - mm[4]) * 0.33333;
+mRb = (mm[1] - mm[0]) * 0.66666;
+mGb = (mm[3] - mm[2]) * 0.66666;
+mBb = (mm[5] - mm[4]) * 0.66666;
+
+size = pimg->width * pimg->height;
+
+for (foo=0; foo<size; foo++) {
+
+	;	// XXX
+
+	}
 
 fprintf(stderr, "the function '%s' is not implemented\n", __func__);
 exit(2);