diff --git a/lib/fimg-2gray.c b/lib/fimg-2gray.c
index 49414cf..7e21ca5 100644
--- a/lib/fimg-2gray.c
+++ b/lib/fimg-2gray.c
@@ -13,7 +13,7 @@ extern int verbosity;		/* must be declared around main() */
 
 /* --------------------------------------------------------------------- */
 /*
- *	floating img MUST be allocated.
+ *	floating imgs MUST be allocated before calling this func.
  */
 int fimg_mk_gray_from(FloatImg *src, FloatImg*dst, int k)
 {
@@ -40,14 +40,13 @@ if (FIMG_TYPE_GRAY != dst->type) {
 nbb = src->width * src->height;
 
 for (foo=0; foo<nbb; foo++) {
-
 	dst->R[foo] = ( (src->R[foo] * kr) +
 			(src->G[foo] * kg) +
 			(src->B[foo] * kb) ) /
 				kdiv;
 	}
 
-return -1;
+return 0;
 }
 /* --------------------------------------------------------------------- */
 
diff --git a/lib/fimg-math.c b/lib/fimg-math.c
index 2f4be78..4647a25 100644
--- a/lib/fimg-math.c
+++ b/lib/fimg-math.c
@@ -20,7 +20,7 @@ float fimg_get_maxvalue(FloatImg *head)
 float		maxval;
 int		foo;
 
-if (head->type != FIMG_TYPE_RGB) {
+if (head->type != FIMG_TYPE_RGB && head->type != FIMG_TYPE_GRAY) {
 	fprintf(stderr, "%s : type %d invalide\n",
 				__func__, head->type);
 	return nanf("wtf ?");
@@ -28,10 +28,17 @@ if (head->type != FIMG_TYPE_RGB) {
 
 maxval = 0.0;		/* no negative values allowed */
 
-for (foo=0; foo<(head->width*head->height); foo++) {
-	if (head->R[foo] > maxval) maxval = head->R[foo];
-	if (head->G[foo] > maxval) maxval = head->G[foo];
-	if (head->B[foo] > maxval) maxval = head->B[foo];
+switch (head->type) {
+	case FIMG_TYPE_RGB:
+		for (foo=0; foo<(head->width*head->height); foo++) {
+		if (head->R[foo] > maxval) maxval = head->R[foo];
+		if (head->G[foo] > maxval) maxval = head->G[foo];
+		if (head->B[foo] > maxval) maxval = head->B[foo];
+		}
+	case FIMG_TYPE_GRAY:
+		for (foo=0; foo<(head->width*head->height); foo++) {
+		if (head->R[foo] > maxval) maxval = head->R[foo];
+		}
 	}
 
 return maxval;
diff --git a/lib/fimg-pnm.c b/lib/fimg-pnm.c
index c36ce69..b642ef8 100644
--- a/lib/fimg-pnm.c
+++ b/lib/fimg-pnm.c
@@ -82,19 +82,69 @@ return 0;
 }
 
 /* ---------------------------------------------------------------- */
+static void dump_gray_values(FILE *fp, FloatImg *picz, float fk)
+{
+int		cnt, sz, value;
+int		idx;
 
+cnt = 0;
+sz = picz->width * picz->height;
+for (idx=0; idx<sz; idx++) {
+	if (fk > 0)	value = (int)(picz->R[idx] / fk);
+	else		value = 0;
+	cnt += fprintf(fp, "%d", value);
+	if (cnt > 70) {
+		fputs("\n", fp); 	cnt = 0;
+		}
+	else	{
+		fputs(" ", fp);		cnt++;
+		}
+	}
+fputs("\n", fp);
+}
+/* ---------------------------------------------------------------- */
+static void dump_rgb_values(FILE *fp, FloatImg *picz, float fk)
+{
+int		cnt, sz, idx;
+int		Rv, Gv, Bv;
+
+cnt = 0;
+sz = picz->width * picz->height;
+for (idx=0; idx<sz; idx++) {
+	if (fk > 0) {
+		Rv = (int)(picz->R[idx] / fk);
+		Gv = (int)(picz->G[idx] / fk);
+		Bv = (int)(picz->B[idx] / fk);
+		}
+	else	{
+		Rv = Gv = Bv = 0;
+		}
+	cnt += fprintf(fp, "%d %d %d", Rv, Gv, Bv);
+	if (cnt > 60) {
+		fputs("\n", fp); 	cnt = 0;
+		}
+	else	{
+		fputs(" ", fp);		cnt++;
+		}
+	}
+fputs("\n", fp);
+}
+/* ---------------------------------------------------------------- */
+/*
+ *
+ */
 int fimg_save_as_pnm(FloatImg *head, char *fname, int notused)
 {
 FILE		*fp;
 float		maximum, fk;
-int		idx, sz, Rv, Gv, Bv, foo;
+char		*code;
 
 #if DEBUG_LEVEL
 fprintf(stderr, ">>> %-25s ( %p '%s' %d )\n", __func__, head,
 						fname, notused);
 #endif
 
-if (head->type != FIMG_TYPE_RGB) {
+if ( head->type != FIMG_TYPE_RGB && head->type != FIMG_TYPE_GRAY) {
 #if DEBUG_LEVEL 
 	fprintf(stderr, "%s : type %d is bad.\n", __func__, head->type);
 #endif
@@ -103,36 +153,32 @@ if (head->type != FIMG_TYPE_RGB) {
 
 if (NULL==(fp=fopen(fname, "w"))) {
 	perror(fname);
-	return -1;
+	return -2;
 	}
 
-fprintf(fp, "P3\n%d %d\n", head->width, head->height);
+switch(head->type) {
+	case FIMG_TYPE_GRAY:	code = "P2";		break;
+	case FIMG_TYPE_RGB:	code = "P3";		break;
+	}
+
+fprintf(fp, "%s\n%d %d\n", code, head->width, head->height);
 
 maximum = fimg_get_maxvalue(head);
 fprintf(fp, "#  maxval  %15f\n", maximum);
 fk = maximum / 65536.0;
 fprintf(fp, "# divisor  %15f\n", fk);
 fprintf(fp, "65535\n");
-sz = head->width*head->height;
+fflush(fp);
 
-foo = 0;
-for (idx=0; idx<sz; idx++) {
-	if (fk > 0) {
-		Rv = (int)(head->R[idx] / fk);
-		Gv = (int)(head->G[idx] / fk);
-		Bv = (int)(head->B[idx] / fk);
-		}
-	else	{
-		Rv = Gv = Bv = 0;
-		}
-	foo += fprintf(fp, "%d %d %d", Rv, Gv, Bv);
-	if (foo > 60) {
-		fputs("\n", fp); 	foo = 0;
-		}
-	else	{
-		fputs(" ", fp);		foo++;
-		}
+switch(head->type) {
+	case FIMG_TYPE_GRAY:
+		dump_gray_values(fp, head, fk);
+		break;
+	case FIMG_TYPE_RGB:
+		dump_rgb_values(fp, head, fk);
+		break;
 	}
+
 fputs("\n", fp);
 
 fclose(fp);