diff --git a/xpick.c b/xpick.c
index c6fc5eb..248f530 100644
--- a/xpick.c
+++ b/xpick.c
@@ -1,10 +1,57 @@
-#include <X11/Xlib.h> 
+/* Copyright (c) 2020 Stefan Hagen <sh+ports@codevoid.de>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #include <X11/cursorfont.h>
 #include <stdio.h>
+#include <string.h>
+#include <unistd.h>
 
+// original implementation in tmux colour.c
+static int rgb_to_x256(uint8_t r, uint8_t g, uint8_t b)
+{
+    // Calculate the nearest 0-based color index at 16 .. 231
+    #define v2ci(v) (v < 48 ? 0 : v < 115 ? 1 : (v - 35) / 40)
+    int ir = v2ci(r), ig = v2ci(g), ib = v2ci(b);   // 0..5 each
+    #define color_index() (36 * ir + 6 * ig + ib)  /* 0..215, lazy evaluation */
 
-int main() {
+    // Calculate the nearest 0-based gray index at 232 .. 255
+    int average = (r + g + b) / 3;
+    int gray_index = average > 238 ? 23 : (average - 3) / 10;  // 0..23
+
+    // Calculate the represented colors back from the index
+    static const int i2cv[6] = {0, 0x5f, 0x87, 0xaf, 0xd7, 0xff};
+    int cr = i2cv[ir], cg = i2cv[ig], cb = i2cv[ib];  // r/g/b, 0..255 each
+    int gv = 8 + 10 * gray_index;  // same value for r/g/b, 0..255
+
+    // Return the one which is nearer to the original input rgb value
+    #define dist_square(A,B,C, a,b,c) ((A-a)*(A-a) + (B-b)*(B-b) + (C-c)*(C-c))
+    int color_err = dist_square(cr, cg, cb, r, g, b);
+    int gray_err  = dist_square(gv, gv, gv, r, g, b);
+    return color_err <= gray_err ? 16 + color_index() : 232 + gray_index;
+}
+
+int main(int argc, char *argv[]) {
+
+    if(argc <= 1) {
+        printf("Usage: xpick [-rhx]\n");
+        printf("    -r   RGB notation RR/GG/BB\n");
+        printf("    -h   HEX notation #RRGGBB\n");
+        printf("    -x   XTerm nearest terminal color\n");
+        return 2;
+    }
 
     Display *dpy = XOpenDisplay(NULL);
     Window root = RootWindow(dpy, DefaultScreen(dpy));
@@ -15,7 +62,7 @@ int main() {
     bgc.red = -1; bgc.green = -1; bgc.blue = -1;
 
     XRecolorCursor(dpy, cursor, &fgc, &bgc);
-    XGrabPointer(dpy, root, 0, ButtonReleaseMask, GrabModeAsync, GrabModeAsync, 
+    XGrabPointer(dpy, root, 0, ButtonReleaseMask, GrabModeAsync, GrabModeAsync,
             None, cursor, CurrentTime);
 
     XEvent event;
@@ -26,10 +73,28 @@ int main() {
 
     unsigned long p = XGetPixel(ximage, 0, 0);
     XDestroyImage(ximage);
-
     XColor result; result.pixel = p;
     XQueryColor(dpy, DefaultColormap(dpy, DefaultScreen(dpy)), &result);
-    printf("#%02x%02x%02x\n",
-            result.red/256, result.green/256, result.blue/256);
+
+    int opt;
+    while((opt = getopt(argc, argv, ":hrx")) != -1){
+        switch(opt){
+            case 'h':
+                printf("#%02x%02x%02x\n",
+                        result.red/256, result.green/256, result.blue/256);
+                break;
+            case 'r':
+                printf("%03d/%03d/%03d\n",
+                        result.red/256, result.green/256, result.blue/256);
+                break;
+            case 'x':
+                printf("%d\n", rgb_to_x256(result.red/256, result.green/256,
+                        result.blue/256));
+                break;
+            case '?': //used for some unknown opts
+                printf("Unknown option: %c\n", optopt);
+                break;
+        }
+    }
     return 0;
 }