diff --git a/.gitignore b/.gitignore
index deb4039..60f208e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,6 +8,7 @@ lib/*.gif
 
 *.a
 gmon.out
+cscope.out
 
 *.swp
 
diff --git a/floatimg.h b/floatimg.h
index b54ea05..fce4fa0 100644
--- a/floatimg.h
+++ b/floatimg.h
@@ -4,7 +4,7 @@
  *	http://la.buvette.org/photos/cumul
  */
 
-#define		FIMG_VERSION	169
+#define		FIMG_VERSION	170
 
 /*
  *	in memory descriptor
@@ -154,6 +154,7 @@ int fimg_export_picture(FloatImg *pic, char *fname, int flags);
 int fimg_save_as_pnm(FloatImg *head, char *fname, int flags);
 int fimg_save_as_pgm(FloatImg *head, char *fname, int flags);
 int fimg_load_from_pnm(char *fname, FloatImg *head, int notused);
+int fimg_save_plane_as_pgm(FloatImg *psrc, char *fname, char plane);
 
 double fimg_timer_set(int whot);
 double fimg_timer_get(int whot);
@@ -222,6 +223,7 @@ int fimg_save_as_exr(FloatImg *src, char *outname, int flags);
 
 
 /*	mathematics operations 				*/
+float fimg_get_plane_maxvalue(FloatImg *psrc, char plane);
 float fimg_get_maxvalue(FloatImg *head);
 int   fimg_get_minmax_rgb(FloatImg *head, float mmvals[6]);
 int   fimg_meanvalues(FloatImg *head, float means[4]);
diff --git a/lib/fimg-math.c b/lib/fimg-math.c
index 0062e7c..365165b 100644
--- a/lib/fimg-math.c
+++ b/lib/fimg-math.c
@@ -16,6 +16,41 @@
 
 extern int verbosity;		/* must be declared around main() */
 
+/* ---------------------------------------------------------------- */
+/* 	nouveau 27 fevrier 2022 */
+float fimg_get_plane_maxvalue(FloatImg *psrc, char plane)
+{
+float		*ptrplane;
+float		maxval;
+int		area, foo;
+
+#if DEBUG_LEVEL
+fprintf(stderr, ">>> %s ( %p '%c' )\n", __func__, psrc, plane);
+#endif
+
+switch (plane) {
+	case 'r':	case 'R':
+		ptrplane = psrc->R;		break;
+	case 'g':	case 'G':
+		ptrplane = psrc->G;		break;
+	case 'b':	case 'B':
+		ptrplane = psrc->B;		break;
+	case 'a':	case 'A':
+		ptrplane = psrc->A;		break;
+	default:
+		fprintf(stderr, "%s: plane error\n", __func__);
+		abort();			break;
+		}
+
+area = psrc->width * psrc->height;
+maxval = 0.0;
+
+for (foo=0; foo<area; foo++) {
+	if (ptrplane[foo] > maxval)	maxval = ptrplane[foo];
+	}
+
+return maxval;
+}
 /* ---------------------------------------------------------------- */
 float fimg_get_maxvalue(FloatImg *head)
 {
diff --git a/lib/fimg-pnm.c b/lib/fimg-pnm.c
index 02dba78..58af3e2 100644
--- a/lib/fimg-pnm.c
+++ b/lib/fimg-pnm.c
@@ -83,6 +83,10 @@ return 0;
 }
 
 /* ---------------------------------------------------------------- */
+/*
+ *	this func write the content of the R channel, the
+ *	only one used by graylevel images
+ */
 static void dump_gray_values(FILE *fp, FloatImg *picz, float fk)
 {
 int		cnt, sz, value;
@@ -112,7 +116,7 @@ int		Rv, Gv, Bv;
 cnt = 0;
 sz = picz->width * picz->height;
 for (idx=0; idx<sz; idx++) {
-	if (fk > 0) {
+	if (fk > 0) {			/* why ? */
 		Rv = (int)(picz->R[idx] / fk);
 		Gv = (int)(picz->G[idx] / fk);
 		Bv = (int)(picz->B[idx] / fk);
@@ -196,10 +200,60 @@ fputs("\n", fp);		fclose(fp);
 return 0;
 }
 /* ---------------------------------------------------------------- */
+/* 	nouveau 27 fevrier 2022 */
+/*				WARNING ! UGLY CODE INSIDE */
+int fimg_save_plane_as_pgm(FloatImg *psrc, char *fname, char plane)
+{
+FILE		*fp;
+float		maxval, fk, *ptrplane;
+int		area, idx, printed;
 
+
+#if DEBUG_LEVEL
+fprintf(stderr, ">>> %s ( %p %s '%c' )\n", __func__, psrc, fname, plane);
+#endif
+
+switch (plane) {
+	case 'r':	case 'R':
+		ptrplane = psrc->R;		break;
+	case 'g':	case 'G':
+		ptrplane = psrc->G;		break;
+	case 'b':	case 'B':
+		ptrplane = psrc->B;		break;
+	case 'a':	case 'A':
+		ptrplane = psrc->A;		break;
+	default:
+		fprintf(stderr, "%s: bad plane '%c'\n", __func__, plane);
+		abort();			break;
+		}
+
+if (NULL==(fp=fopen(fname, "w"))) {
+	perror(fname);
+	return -2;
+	}
+
+fprintf(fp, "P2\n%d\n%d\n65535\n\n", psrc->width, psrc->height);
+area = psrc->width * psrc->height;
+maxval = fimg_get_plane_maxvalue(psrc, plane);
+fk = maxval / 65535.0;
+
+fprintf(stderr, "%s: maxval of %c = %f\n", __func__, plane, maxval);
+
+printed = 0;
+for (idx=0; idx<area; idx++) {
+	printed += fprintf(fp, "%d ", (int)(ptrplane[idx]/fk));
+	if (printed > 72) {
+		fputs("\n", fp);
+		printed = 0;
+		}
+	}
+
+fclose(fp);
+
+return -1;
+}
+/* ---------------------------------------------------------------- */
 /* 	nouveau 10 fevrier 2022 */
-
-
 int fimg_save_as_pgm(FloatImg *src, char *fname, int flags)
 {
 FILE		*fp;
diff --git a/lib/t.c b/lib/t.c
index 562c853..8c510af 100644
--- a/lib/t.c
+++ b/lib/t.c
@@ -14,6 +14,25 @@
 
 int		verbosity;
 
+/* ---------------------------------------------------------------- */
+int essai_save_plane(int wot)
+{
+int		foo;
+FloatImg	image;
+
+fprintf(stderr, "-------- %s ( %d ) --------\n", __func__, wot);
+
+foo = fimg_create_from_dump("grabbed.fimg", &image);
+if (foo) {
+	fprintf(stderr, "err loading picz\n");
+	return -6;
+	}
+foo = fimg_save_plane_as_pgm(&image, "red.pgm", 'r');
+foo = fimg_save_plane_as_pgm(&image, "green.pgm", 'g');
+foo = fimg_save_plane_as_pgm(&image, "blue.pgm", 'b');
+
+return 0;
+}
 /* ---------------------------------------------------------------- */
 int essai_timer(int uuuh)
 {
@@ -269,7 +288,7 @@ if (verbosity)	{
 	fimg_print_sizeof();
 	}
 
-foo = essai_2gray(NULL, "quux");
+foo = essai_save_plane(0);
 fprintf(stderr, "retour essai  -> %d\n", foo);
 
 // foo = essai_clone_et_copy(0);