How to return image using TYK virtual endpoint

i would like to return a image using TYK virtual endpoint, already get the based-64 encode string,try to set the response content-type to “image/png”, but when test with postman, the image will display with bad image.

My virtual endpoint configuration:

function test(request, session, config) {
var baseString = “base64 encode string”;
var responseObject = {
Headers: {
“content-type”: “image/png”
Code: 200
return TykJsResponse(responseObject, session.meta_data)