add a new function

lib/fimg-core.c

@@ -164,6 +164,28 @@ if ( ! fimg_type_is_valid(fimg->type) ) {
 size = fimg->width * fimg->height * fimg->type * sizeof(float);
 memset(fimg->R, 0, size);
 
+return 0;
+}
+/* --------------------------------------------------------------------- */
+int fimg_rgb_constant(FloatImg *head, float r, float g, float b)
+{
+int		idx, size;
+
+fprintf(stderr, ">>> %-25s ( %p %f %f %f )\n", __func__, head,
+				r, g, b);
+
+if (head->type != FIMG_TYPE_RGB) {
+	return -21;
+	}
+
+size = head->width * head->height;
+
+for (idx=0; idx<size; idx++) {
+	head->R[idx] = r;
+	head->G[idx] = g;
+	head->B[idx] = b;
+	}
+
 return 0;
 }
 /* --------------------------------------------------------------------- */