I in web page index in the HTML display real-time monitoring video, in this web page loading an iframe, iframe set to transparent, and he made a new HTML web page, the page load a echarts control display data figure, echarts controls are set to transparent, load in the iframe. New HTML web page display effect as shown in figure, how do I let the monitor screen can be displayed by setting the transparent iframe, that is to say the iframe background is real-time monitoring the picture?