diff --git a/undither.html b/undither.html
new file mode 100644
index 0000000..e7d351d
--- /dev/null
+++ b/undither.html
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+<html>
+  <head>
+    <title>Undither</title>
+    <script>
+function toRgbTable(col)
+{
+  // return a color in the form [red, green, blue] for a hex #RRGGBB
+  return [parseInt(col.slice(1,3), 16), parseInt(col.slice(3,5), 16), parseInt(col.slice(5,7), 16)]
+}
+function toRgbHex(col)
+{
+  // return a color in the hex for from a [red, green, blue]
+  pf_red = ""
+  pf_green = ""
+  pf_blue = ""
+  if (col[0] < 16) pf_red = "0"
+  if (col[1] < 16) pf_green = "0"
+  if (col[2] < 16) pf_blue = "0"
+  return "#" + pf_red + col[0].toString(16) + pf_green + col[1].toString(16) + pf_blue + col[2].toString(16)
+}
+function updateColor()
+{
+  val_1 = document.getElementById("col_1").value
+  val_2 = document.getElementById("col_2").value
+  val_3 = document.getElementById("col_3").value
+  val_4 = document.getElementById("col_4").value
+  rgb_1 = toRgbTable(val_1)
+  rgb_2 = toRgbTable(val_2)
+  rgb_3 = toRgbTable(val_3)
+  rgb_4 = toRgbTable(val_4)
+  rgb_res = [0, 0, 0]
+  rgb_res[0] = Math.floor((rgb_1[0] + rgb_2[0] + rgb_3[0] + rgb_4[0]) / 4)
+  rgb_res[1] = Math.floor((rgb_1[1] + rgb_2[1] + rgb_3[1] + rgb_4[1]) / 4)
+  rgb_res[2] = Math.floor((rgb_1[2] + rgb_2[2] + rgb_3[2] + rgb_4[2]) / 4)
+  res = toRgbHex(rgb_res)
+
+  col_res = document.getElementById("col_res")
+  col_res.innerText = res
+  in_res = document.getElementById("in_res")
+  in_res.value = res
+}
+    </script>
+  </head>
+  <body onload="updateColor();">
+    <div>
+      <input id="col_1" type="color" value="#ffffff" onchange="updateColor();" />
+      <input id="col_2" type="color" value="#000000" onchange="updateColor();" />
+    </div>
+    <div>
+      <input id="col_3" type="color" value="#000000" onchange="updateColor();" />
+      <input id="col_4" type="color" value="#ffffff" onchange="updateColor();" />
+    </div>
+    <p>Result: <span id="col_res"></span> <input id="in_res" type="color" value="#000000" /></p>
+  </body>
+</html>
