function getImageHeight70Percent(obj) {
	obj = document.getElementById(obj);
	
	var newImg = new Image();
    newImg.src = obj.src;
    var height = newImg.height;
	
	if (height > screen.height * 0.7) {
	 obj.height = screen.height * 0.7;
	}
	else {	
	 obj.height = height;  	
	}
	
  }