diff --git a/floatimg.h b/floatimg.h
index ebf8cea..7bb505e 100644
--- a/floatimg.h
+++ b/floatimg.h
@@ -143,6 +143,7 @@ int   fimg_load_from_png(char *filename, FloatImg *fimg);
 int   fimg_create_from_png(char *filename, FloatImg *fimg);
 int   fimg_save_as_png(FloatImg *src, char *outname, int flags);
 
+int   fimg_test_pattern(FloatImg *fimg, int type, double dval);
 int   fimg_draw_something(FloatImg *fimg);
 
 int parse_WxH(char *str, int *pw, int *ph);
diff --git a/funcs/misc-plots.c b/funcs/misc-plots.c
index ae730e4..5bcfbf8 100644
--- a/funcs/misc-plots.c
+++ b/funcs/misc-plots.c
@@ -11,6 +11,57 @@
 
 /* --------------------------------------------------------------------- */
 
+int fimg_test_pattern(FloatImg *fimg, int type, double dval)
+{
+int		nio;
+int		x, y;
+float		fr, fg, fb;
+
+#if DEBUG_LEVEL
+fprintf(stderr, ">>> %s ( %p %d %g )\n", __func__, fimg, type, dval);
+#endif
+
+if (fimg->type != FIMG_TYPE_RGB) {
+	fprintf(stderr, "%s need an rgb pic\n", __func__);
+	return -6;
+	}
+
+/* rampe de primaires dans le quart du haut */
+
+for (x=0; x<fimg->width; x++) {
+
+	nio = x / (fimg->width / 8);
+
+	switch(nio) {
+		case 0:
+			fr = 0.0, fg = 0.0, fb = 0.0;	break;
+		case 1:
+			fr = 1.0, fg = 0.0, fb = 0.0;	break;
+		case 2:
+			fr = 0.0, fg = 1.0, fb = 0.0;	break;
+		case 3:
+			fr = 1.0, fg = 1.0, fb = 0.0;	break;
+		case 4:
+			fr = 0.0, fg = 0.0, fb = 1.0;	break;
+		case 5:
+			fr = 1.0, fg = 0.0, fb = 1.0;	break;
+		case 6:
+			fr = 0.0, fg = 1.0, fb = 1.0;	break;
+		case 7:
+			fr = 1.0, fg = 1.0, fb = 1.0;	break;
+		default:
+			// abort();
+			break;
+		}
+
+	for (y=0; y<fimg->height/4; y++)
+			fimg_plot_rgb(fimg, x, y, fr, fg, fb);
+
+	}
+
+return -1;
+}
+/* --------------------------------------------------------------------- */
 int fimg_draw_something(FloatImg *fimg)
 {
 int	x, y;