My suggestion is the following:
js code:
var oGdip = new Gdip();
if ( oGdip.Initialize() === true ) {
>>> oGdip.ConvertImage( 'C:\\myImage.png', 'C:\\myImage'+new Date().getTime()+'.jpg', 'JPG', 75 );<<<
Debug.Trace( oGdip.GetImageDimensions( 'C:\\myImage.jpg' ) );
oGdip.Uninitialize();
} else Debug.Trace ( 'An error occured while initializing Gdi+' );
Then you can load the new JPG file and overwrite the PNG. Then you can create as many windows as needed as long as you load the latest image