diff --git a/sys/teken/libteken/teken.3 b/sys/teken/libteken/teken.3
index 70bed07a57b..b42405f07c0 100644
--- a/sys/teken/libteken/teken.3
+++ b/sys/teken/libteken/teken.3
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 9, 2011
+.Dd Mar 13, 2017
 .Dt TEKEN 3
 .Os
 .Sh NAME
@@ -57,6 +57,8 @@
 .Ft const char *
 .Fn teken_get_sequence "teken_t *t" "unsigned int id"
 .Ft teken_color_t
+.Fn teken_256to16 "teken_color_t color"
+.Ft teken_color_t
 .Fn teken_256to8 "teken_color_t color"
 .Ft void
 .Fn teken_get_defattr_cons25 "teken_t *t" "int *fg" "int *bg"
@@ -163,10 +165,22 @@ This library also provides a set of functions that shouldn't be used in
 any modern applications.
 .Pp
 The
+.Fn teken_256to16
+function converts an xterm-256 256-color code to an xterm 16-color code
+whose color with default palettes is as similar as possible (not very
+similar).
+The lower 3 bits of the result are the ANSI color and the next lowest
+bit is brightness.
+Other layers (hardare and software) that only support 16 colors can use
+this to avoid knowing the details of 256-color codes.
+.Pp
+The
 .Fn teken_256to8
-function converts a color code to one of the 8 primary colors, allowing
-the terminal to be rendered on graphics hardware that only supports 8 or
-16 colors (e.g. VGA).
+function is similar to
+.Fn teken_256to16
+except it converts to an ANSI 8-color code.
+This is more accurate than discarding the brigtness bit in the result of
+.Fn teken_256to16 .
 .Pp
 The
 .Fn teken_get_defattr_cons25
diff --git a/sys/teken/teken.c b/sys/teken/teken.c
index 8834390dec4..6a9842d5384 100644
--- a/sys/teken/teken.c
+++ b/sys/teken/teken.c
@@ -452,55 +452,203 @@ teken_state_numbers(teken_t *t, teken_char_t c)
 	return (0);
 }
 
+#define	k	TC_BLACK
+#define	b	TC_BLUE
+#define	y	TC_BROWN
+#define	c	TC_CYAN
+#define	g	TC_GREEN
+#define	m	TC_MAGENTA
+#define	r	TC_RED
+#define	w	TC_WHITE
+#define	K	(TC_BLACK | TC_LIGHT)
+#define	B	(TC_BLUE | TC_LIGHT)
+#define	Y	(TC_BROWN | TC_LIGHT)
+#define	C	(TC_CYAN | TC_LIGHT)
+#define	G	(TC_GREEN | TC_LIGHT)
+#define	M	(TC_MAGENTA | TC_LIGHT)
+#define	R	(TC_RED | TC_LIGHT)
+#define	W	(TC_WHITE | TC_LIGHT)
+
+/**
+ * The xterm-256 color map has steps of 0x28 (in the range 0-0xff), except
+ * for the first step which is 0x5f.  Scale to the range 0-6 by dividing
+ * by 0x28 and rounding down.  The range of 0-5 cannot represent the
+ * larger first step.
+ *
+ * This table is generated by the follow rules:
+ * - if all components are equal, the result is black for (0, 0, 0) and
+ *   (2, 2, 2), else white; otherwise:
+ * - subtract the smallest component from all components
+ * - if this gives only one nonzero component, then that is the color
+ * - else if one component is 2 or more larger than the other nonzero one,
+ *   then that component gives the color
+ * - else there are 2 nonzero components.  The color is that of a small
+ *   equal mixture of these components (cyan, yellow or magenta).  E.g.,
+ *   (0, 5, 6) (Turquoise2) is a much purer cyan than (0, 2, 3)
+ *   (DeepSkyBlue4), but we map both to cyan since we can't represent
+ *   delicate shades of either blue or cyan and blue would be worse.
+ *   Here it is important that components of 1 never occur.  Blue would
+ *   be twice as large as green in (0, 1, 2).
+ */
+static const teken_color_t teken_256to8tab[] = {
+	/* xterm-16+ 8 dark colors: */
+	0, r, g, y, b, m, c, w,
+
+	/* xterm-16+ 8 light colors: */
+	0, R, G, Y, B, M, C, W,
+
+	/* Red0 submap. */
+	k, b, b, b, b, b,
+	g, c, c, b, b, b,
+	g, c, c, c, b, b,
+	g, g, c, c, c, b,
+	g, g, g, c, c, c,
+	g, g, g, g, c, c,
+
+	/* Red2 submap. */
+	r, m, m, b, b, b,
+	y, k, b, b, b, b,
+	y, g, c, c, b, b,
+	g, g, c, c, c, b,
+	g, g, g, c, c, c,
+	g, g, g, g, c, c,
+
+	/* Red3 submap. */
+	r, m, m, m, b, b,
+	y, r, m, m, b, b,
+	y, y, w, b, b, b,
+	y, y, g, c, c, b,
+	g, g, g, c, c, c,
+	g, g, g, g, c, c,
+
+	/* Red4 submap. */
+	r, r, m, m, m, b,
+	r, r, m, m, m, b,
+	y, y, r, m, m, b,
+	y, y, y, w, b, b,
+	y, y, y, g, c, c,
+	g, g, g, g, c, c,
+
+	/* Red5 submap. */
+	r, r, r, m, m, m,
+	r, r, r, m, m, m,
+	r, r, r, m, m, m,
+	y, y, y, r, m, m,
+	y, y, y, y, w, b,
+	y, y, y, y, g, c,
+
+	/* Red6 submap. */
+	r, r, r, r, m, m,
+	r, r, r, r, m, m,
+	r, r, r, r, m, m,
+	r, r, r, r, m, m,
+	y, y, y, y, r, m,
+	y, y, y, y, y, w,
+
+	/* Grey submap. */
+	k, k, k, k, k, k,
+	k, k, k, k, k, k,
+	w, w, w, w, w, w,
+	w, w, w, w, w, w,
+};
+
+/*
+ * This table is generated from the previous one by setting TC_LIGHT for
+ * entries whose luminosity in the xterm256 color map is 60% or larger.
+ * Thus the previous table is currently not really needed.  It will be
+ * used for different fine tuning of the tables.
+ */
+static const teken_color_t teken_256to16tab[] = {
+	/* xterm-16+ 8 dark colors: */
+	0, r, g, y, b, m, c, w,
+
+	/* xterm-16+ 8 light colors: */
+	0, R, G, Y, B, M, C, W,
+
+	/* Red0 submap. */
+	k, b, b, b, b, b,
+	g, c, c, b, b, b,
+	g, c, c, c, b, b,
+	g, g, c, c, c, b,
+	g, g, g, c, c, c,
+	g, g, g, g, c, c,
+
+	/* Red2 submap. */
+	r, m, m, b, b, b,
+	y, K, b, b, B, B,
+	y, g, c, c, B, B,
+	g, g, c, c, C, B,
+	g, G, G, C, C, C,
+	g, G, G, G, C, C,
+
+	/* Red3 submap. */
+	r, m, m, m, b, b,
+	y, r, m, m, B, B,
+	y, y, w, B, B, B,
+	y, y, G, C, C, B,
+	g, G, G, C, C, C,
+	g, G, G, G, C, C,
+
+	/* Red4 submap. */
+	r, r, m, m, m, b,
+	r, r, m, m, M, B,
+	y, y, R, M, M, B,
+	y, y, Y, W, B, B,
+	y, Y, Y, G, C, C,
+	g, G, G, G, C, C,
+
+	/* Red5 submap. */
+	r, r, r, m, m, m,
+	r, R, R, M, M, M,
+	r, R, R, M, M, M,
+	y, Y, Y, R, M, M,
+	y, Y, Y, Y, W, B,
+	y, Y, Y, Y, G, C,
+
+	/* Red6 submap. */
+	r, r, r, r, m, m,
+	r, R, R, R, M, M,
+	r, R, R, R, M, M,
+	r, R, R, R, M, M,
+	y, Y, Y, Y, R, M,
+	y, Y, Y, Y, Y, W,
+
+	/* Grey submap. */
+	k, k, k, k, k, k,
+	K, K, K, K, K, K,
+	w, w, w, w, w, w,
+	W, W, W, W, W, W,
+};
+
+#undef	k
+#undef	b
+#undef	y
+#undef	c
+#undef	g
+#undef	m
+#undef	r
+#undef	w
+#undef	K
+#undef	B
+#undef	Y
+#undef	C
+#undef	G
+#undef	M
+#undef	R
+#undef	W
+
 teken_color_t
 teken_256to8(teken_color_t c)
 {
-	unsigned int r, g, b;
 
-	if (c < 16) {
-		/* Traditional color indices. */
-		return (c % 8);
-	} else if (c >= 244) {
-		/* Upper grayscale colors. */
-		return (TC_WHITE);
-	} else if (c >= 232) {
-		/* Lower grayscale colors. */
-		return (TC_BLACK);
-	}
+	return (teken_256to8tab[c % 256]);
+}
 
-	/* Convert to RGB. */
-	c -= 16;
-	b = c % 6;
-	g = (c / 6) % 6;
-	r = c / 36;
+teken_color_t
+teken_256to16(teken_color_t c)
+{
 
-	if (r < g) {
-		/* Possibly green. */
-		if (g < b)
-			return (TC_BLUE);
-		else if (g > b)
-			return (TC_GREEN);
-		else
-			return (TC_CYAN);
-	} else if (r > g) {
-		/* Possibly red. */
-		if (r < b)
-			return (TC_BLUE);
-		else if (r > b)
-			return (TC_RED);
-		else
-			return (TC_MAGENTA);
-	} else {
-		/* Possibly brown. */
-		if (g < b)
-			return (TC_BLUE);
-		else if (g > b)
-			return (TC_BROWN);
-		else if (r < 3)
-			return (TC_BLACK);
-		else
-			return (TC_WHITE);
-	}
+	return (teken_256to16tab[c % 256]);
 }
 
 static const char * const special_strings_cons25[] = {
diff --git a/sys/teken/teken.h b/sys/teken/teken.h
index 27d1ce40474..7e3716bec55 100644
--- a/sys/teken/teken.h
+++ b/sys/teken/teken.h
@@ -56,6 +56,7 @@ typedef unsigned char teken_color_t;
 #define	TC_CYAN		6
 #define	TC_WHITE	7
 #define	TC_NCOLORS	8
+#define	TC_LIGHT	8	/* ORed with the others. */
 
 typedef struct {
 	teken_unit_t	tp_row;
@@ -203,6 +204,7 @@ void	teken_set_8bit(teken_t *);
 void	teken_set_cons25(teken_t *);
 
 /* Color conversion. */
+teken_color_t teken_256to16(teken_color_t);
 teken_color_t teken_256to8(teken_color_t);
 
 #endif /* !_TEKEN_H_ */