Scaling Group of Text and ImageView inside StackPane - javafx

Question

I need to get image and text above. I create StackPane and put ImageView and Group with Text elements inside. I want to resize my StackPane and keep ImageView proportions and position of Group of Texts over this ImageView. Code below works, but when i resize StackPane i cant fix Group of Texts position.
Small window. Top of text on the top of image
Big window. Top of text lower than top of image
public class SlideFromText extends Slide {
private StackPane sp = new StackPane();
private ImageView iv = new ImageView();
private Group text_group = new Group();
public SlideFromText(Image img, String text_string) {
iv.setImage(img);
iv.setPreserveRatio(true);
iv.fitWidthProperty().bind(sp.widthProperty());
iv.fitHeightProperty().bind(sp.heightProperty());
sp.setAlignment(Pos.TOP_CENTER);
sp.setMinSize(0, 0);
sp.getChildren().add(iv);
String lines[] = text_string.split("\\r?\\n");
double height = 0;
double maxWidth = 0;
String font_name = (String) Options.getOption("font");
Font f = new Font(font_name, 20);
ArrayList<Text> text_array = new ArrayList<>();
for (String line : lines) {
Text text = new Text(line);
text.setFont(f);
text.setFill(Color.WHITE);
text.setTextOrigin(VPos.BASELINE);
text.setTextAlignment(TextAlignment.CENTER);
DropShadow sh = new DropShadow(3, Color.BLACK);
sh.setSpread(0.25);
text.setEffect(sh);
height += text.getBoundsInParent().getHeight();
text.setY(height);
text.setX(sh.getRadius() / 2);
maxWidth = Math.max(maxWidth, text.getBoundsInParent().getWidth());
text_array.add(text);
}
for (Text t : text_array) {
t.setWrappingWidth(maxWidth);
}
text_group.getChildren().addAll(text_array);
sp.getChildren().add(text_group);
iv.boundsInParentProperty().addListener(new ChangeListener<Bounds>() {
#Override
public void changed(ObservableValue<? extends Bounds> observable, Bounds oldValue, Bounds newValue) {
Node node = sp.getChildren().get(1);
if (node.getClass() != Group.class) {
return;
}
Group group_node = (Group) node;
group_node.setLayoutX(-1.0 * group_node.layoutBoundsProperty().get().getWidth() / 2.0);
group_node.getTransforms().clear();
double scale_x = (iv.getBoundsInParent().getWidth() * 0.95) / group_node.getBoundsInParent().getWidth();
double scale_y = (iv.getBoundsInParent().getHeight() * 0.95) / group_node.getBoundsInParent().getHeight();
double scale_factor = Math.min(scale_x, scale_y);
double pivot_x = (group_node.getBoundsInLocal().getMaxX() - group_node.getBoundsInLocal().getMinX()) / 2;
Scale scale = new Scale(scale_factor, scale_factor, pivot_x, 0);
group_node.getTransforms().add(scale);
}
});
}
#Override
public Pane getPane() {
return sp;
}
}