diff --git a/floatimg.h b/floatimg.h
index afb0829d..a3e5d03a 100644
--- a/floatimg.h
+++ b/floatimg.h
@@ -79,6 +79,7 @@ int   fimg_to_gray(FloatImg *head);
 void  fimg_add_cste(FloatImg *fi, float value);
 void  fimg_mul_cste(FloatImg *fi, float value);
 void  fimg_drand48(FloatImg *fi, float kmul);
+int   fimg_count_negativ(FloatImg *fi);
 
 /*	various funcs modules		*/
 int   fimg_load_from_png(char *filename, FloatImg *fimg);
diff --git a/lib/fimg-math.c b/lib/fimg-math.c
index d8513b04..873f3229 100644
--- a/lib/fimg-math.c
+++ b/lib/fimg-math.c
@@ -108,6 +108,27 @@ for (idx=0; idx<nbre; idx++) {
 	}
 }
 /* ---------------------------------------------------------------- */
+int fimg_count_negativ(FloatImg *fi)
+{
+int		nbre, idx;
+int		count;
+
+if (fi->type != FIMG_TYPE_RGB) {
+	fprintf(stderr, "%s : type %d invalide\n",
+				__func__, fi->type);
+	return -1;
+	}
+
+nbre = fi->width * fi->height * fi->type;
+
+count = 0;
+for (idx=0; idx<nbre; idx++) {
+	if (fi->R[idx] < 0.0) count++;
+	}
+
+return count;
+}
+/* ---------------------------------------------------------------- */
 void  fimg_mul_cste(FloatImg *fi, float value)
 {
 int		nbre, idx;
diff --git a/tools/fimgstats.c b/tools/fimgstats.c
index d5306020..8642e46c 100644
--- a/tools/fimgstats.c
+++ b/tools/fimgstats.c
@@ -31,7 +31,12 @@ for (foo=0; foo<4; foo++)
 	printf("      %c   %14.6f\n", "RGBA"[foo], moyennes[foo]);
 
 fvalue = fimg_get_maxvalue(fimg);
-printf("max value     %f\n", fvalue);
+printf("max value       %f\n", fvalue);
+
+foo = fimg_count_negativ(fimg);
+if (foo) {
+	fprintf(stderr, "%d negative values\n", foo);
+	}
 
 return 0;
 }