paper.localToPaperRect(rect)

Transform the rectangle rect defined in the local coordinate system to the paper coordinate system.

var bbox = element.getBBox();
var paperRect1 = paper.localToPaperRect(bbox);
 // alternative method signature
var paperRect2 = paper.localToPaperRect(bbox.x, bbox.y, bbox.width, bbox.height);
// Draw an HTML rectangle above the element.
var div = document.createElement('div');
div.style.position = 'absolute';
div.style.background = 'red';
div.style.left = paperRect1.x + 'px';
div.style.top = paperRect1.y + 'px';
div.style.width = paperRect1.width + 'px';
div.style.height = paperRect1.height + 'px';
paper.el.appendChild(div);