Added globalAlpha example

examples/globalAlpha.js

@@ -0,0 +1,30 @@
+
+/**
+ * Module dependencies.
+ */
+
+var Canvas = require('../lib/canvas')
+  , canvas = new Canvas(150, 150)
+  , ctx = canvas.getContext('2d');
+
+ctx.fillStyle = '#FD0';
+ctx.fillRect(0,0,75,75);
+ctx.fillStyle = '#6C0';
+ctx.fillRect(75,0,75,75);
+ctx.fillStyle = '#09F)';
+ctx.fillRect(0,75,75,75);
+ctx.fillStyle = '#F30';
+ctx.fillRect(75,75,150,150);
+ctx.fillStyle = '#FFF';
+
+// set transparency value
+ctx.globalAlpha = 0.2;
+
+// Draw semi transparent circles
+for (i=0;i<7;i++){
+    ctx.beginPath();
+    ctx.arc(75,75,10+10*i,0,Math.PI*2,true);
+    ctx.fill();
+}
+
+canvas.savePNG(__dirname + '/globalAlpha.png');