Added spark example

examples/spark.js

@@ -0,0 +1,40 @@
+
+/**
+ * Module dependencies.
+ */
+
+var Canvas = require('../lib/canvas')
+  , canvas = new Canvas(40, 15)
+  , ctx = canvas.getContext('2d');
+
+Object.defineProperty(Array.prototype, 'max', {
+  get: function(){
+    var max = 0;
+    for (var i = 0, len = this.length; i < len; ++i) {
+      var n = this[i];
+      if (n > max) max = n;
+    }
+    return max;
+  }
+});
+
+function spark(ctx, color, data) {
+  var len = data.length
+    , pad = 1
+    , width = ctx.canvas.width
+    , height = ctx.canvas.height
+    , barWidth = width / len
+    , max = data.max;
+  ctx.fillStyle = color;
+  data.forEach(function(n, i){
+    ctx.fillRect(
+        i * barWidth + pad
+      , height
+      , barWidth - pad
+      , -(height * (n / max)));
+  });
+}
+
+spark(ctx, 'blue', [1,2,4,5,10,4,2,5,4,3,3,2]);
+
+canvas.savePNG(__dirname + "/spark.png");