many changes

gradientmesh/util.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env ipython
+def clamp(val, low, high):
+    return min(high, max(low, val))
+
+
+def rgb2hex(r, g, b, a=None):
+    hex_value = "#{:02x}{:02x}{:02x}".format(
+        int(r * 255),
+        int(g * 255),
+        int(b * 255)
+    )
+    return hex_value