diff --git a/funcs/saturation.c b/funcs/saturation.c
index bb7f007..8c53b16 100644
--- a/funcs/saturation.c
+++ b/funcs/saturation.c
@@ -1,5 +1,5 @@
 /*
- *	FloatImg library from tTh
+ *	FloatImg library from tTh - ugly code inside
  */
 
 #include  <stdio.h>
@@ -12,7 +12,10 @@
 extern	int	verbosity;
 
 /* -------------------------------------------------------------- */
-
+/*
+ *	parameter mix is between 0.0 and 1.0 but other
+ *	values give sometime good vibrations.
+ */
 int fimg_mix_rgb_gray(FloatImg *img, float mix)
 {
 int		x, y, p;
@@ -24,7 +27,8 @@ if (FIMG_TYPE_RGB != img->type) {
 	}
 
 for (y=0; y<img->height; y++) {
-	p = y * img->width;
+	p = y * img->width;		/* first pixel of the row */
+
 	for (x=0; x<img->width; x++) {
 
 		gr = (img->R[p] + img->G[p] + img->R[p]) / 3.0;
@@ -42,17 +46,21 @@ return 0;
 }
 
 /* -------------------------------------------------------------- */
+/*
+ *	The third parameter was a six value array with min and max
+ *	values maybe computed by the 'fimg_get_minmax_rgb' function.
+ */
 int     fimg_shift_to_zero(FloatImg *s, FloatImg *d, float coefs[6])
 {
 int             sz, idx;
 
-sz = s->width * s->height;
-
 if (FIMG_TYPE_RGB != s->type) {
 	fprintf(stderr, "%s bad type\n", __func__);
 	return -6;
 	}
 
+sz = s->width * s->height;
+
 for (idx=0; idx<sz; idx++) {
 	d->R[idx] = s->R[idx] - coefs[0];
 	d->G[idx] = s->G[idx] - coefs[2];