Unsolved QWebEngineView img label display QPixmap

[anning]

Hi, all
c++:
signals:
void signalImage(QPixmap img);

js:
bound.signalImage.connect(function(img){
//<img id='imgid'></img>
var imgid = document.getElementById("imgid");
//img is QPixmap
imgid .src=??
});

QWebkit assignToHTMLImageElement no problem
but it's not going to work QWebEngineView assignToHTMLImageElement
error:js: Uncaught TypeError: Cannot read property 'assignToHTMLImageElement' of null
i didn't get it right anywhere?