Merge pull request beyondscreen#24 from usefulthink/new-index-mapping

add new index-mapping for LED-panels wired in alternating rows

Author: usefulthink

lib/index-mapping/alternating-matrix.js

@@ -0,0 +1,14 @@
+module.exports = function(width, height) {
+    var map = new Uint16Array(width*height);
+    for(var i = 0; i<map.length; i++) {
+        var row = Math.floor(i/width), col = i % width;
+
+        if((row % 2) === 0) {
+            map[i] = i;
+        } else {
+            map[i] = (row+1) * width - (col+1);
+        }
+    }
+
+    return map;
+};