如何将html5画布图像保存到SQL Server

Question

我在aspsnippets.com上找到了这段代码。我成功运行它，直到运行网页，并能够绘制签名，然后将其保存到屏幕上的另一个html图像。但是我想把这个图像放到我的数据库中。如何从我的.aspx.vb页面调用html？

<div class="tools">
<a href="#colors_sketch" data-tool="marker">Marker</a> <a href="#colors_sketch" data-tool="eraser">
    Eraser</a>
</div>
<br />
<canvas id="colors_sketch" width="500" height="200" style = "border:3px solid #ccc">
</canvas>
<br />
<br />
<input type="button" id="btnSave" value="Save as Image"/>
<hr />
<img id = "imgCapture" alt = "" style = "display:table-cell;border:1px solid #ccc"  />

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script src="http://intridea.github.io/sketch.js/lib/sketch.min.js" type="text/javascript"></script>

<script type="text/javascript">
$(function () {
    $('#colors_sketch').sketch();
    $(".tools a").eq(0).attr("style", "color:#000");
    $(".tools a").click(function () {
        $(".tools a").removeAttr("style");
        $(this).attr("style", "color:#000");
    });
    $("#btnSave").bind("click", function () {
        var base64 = $('#colors_sketch')[0].toDataURL();
        $("#imgCapture").attr("src", base64);
        $("#imgCapture").show();
    });
});
</script>