 
     canvas = document.getElementById("canvas")
     context = canvas.getContext("2d")
-    canvas.width = 3072
-    canvas.height = 2048
+    canvas.width = 1536
+    canvas.height = 1024
 
     color = (height) ->
         r = 128

        "#" + hexR + hexG + hexB

    viewer.paint = (data) ->
        context.clearRect(0, 0, 3072, 2048)

        [num, len, heights] = data
        width = 1024 / num

                pos = row * num + row + col
                height = heights[pos] / 64
                context.fillStyle = color(height)
                context.fillRect(1.5 * width * col, width * row, 1.5 * width, width)

    viewer