capture.html

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
		<script type="text/javascript" src="C:\Temp\AJA\Autodesk.AutoCAD.js"></script>
        <title>Sample App</title>
		<script>
			
		function capturePreview()
		{		
				Acad.Application.activedocument.capturePreview(200,200)
.then(success,error);
		}
		function success(encodedbmp)
		{
			var container = document.getElementById('imageContainer');
            var img = document.createElement('img');
            var src = "data:image/bmp;base64," + encodedbmp;
            img.setAttribute('src', src);
            img.setAttribute('id', 'previewImg');
            container.appendChild(img);
		}

		function error()
		{
			alert("error");
		}

		</script>
    </head>
    <body>
		<input type='button' onclick='window.location.reload()' 
value='Reload' style="display:inline"/>
        <h1>Sample App</h1>
		<input type='button' onclick='capturePreview()' 
value="capturePreview"/>
		<div id='imageContainer'></div>
        <p>
        </p>
    </body>
</html>