in gs2 it's getimgwidth("name.png"); and you can't set the width with it.
as i said you can just use
PHP Code:
with(showimg(200,"image.png",x,y)) {
stretchx = 300/getimgwidth("image.png");
}
Will make the image 300px wide on screen.
n.b. the only issue with this is that X and Y of the showimg will not be in the top left corner of the image any more.