How download in png a svg made with Mxgraph

Question

I'm using Mxgraph to do a diagram tool, in this tool I have some images that I need to make my diagrams. I use insertVertx to add images like this:

const IMAGE = 'routeimage.png';

    const vertex = graph.insertVertex(
    parent,
    null,
    '',
    x,
    y,
    width,
    height,
    'shape=image;image=' + IMAGE
    );

When I try to download the svg like .png the image that I add using insertVertex doesnt show