JavaFX reset graphics Context after scaling a canvas - graphics

Question

I'm trying to make a chart without using any 3rd party libs. I've a zoom feature which scales the Canvas correctly, but now I need to redraw everything inside the canvas once again.
But when I do scaling the GrapphicsContext also scales and blots. I want to readjust the blotting and show points in normal drawing once zoomed. How can I achieve this?
Here is simple snippet that I'm redrawing:
private void redrawImage(Canvas canvas, int scale) {
GraphicsContext gc = canvas.getGraphicsContext2D();
gc.clearRect(0, 0, canvas.getWidth(), canvas.getHeight());
gc.scale(scale, scale);
gc.setStroke(Color.RED);
gc.setLineWidth(2);
gc.strokeRect(0, 0, canvas.getWidth(), canvas.getHeight());
gc.setStroke(Color.GREEN);
gc.strokeLine(0, 0, canvas.getWidth(), canvas.getHeight());
gc.strokeLine(0, canvas.getHeight(), canvas.getWidth(), 0);
gc.setStroke(Color.BLUE);
gc.strokeText("TEXT", 50, 50);
}
Even I remove gc.scale(X,Y) I still see the blotted points or text, I want the scale to be always 1, but I should also zoom or scale simultaneously.
What I want to achieve is like the GoogleMaps overlaying, you see the objects when zoomed in or out are recalibrated and adjusted to a viewable scale. This is exactly what I want to achieve.

Answer 1

I don't know if I understand you correct.
Your redrawImage method should get an double and not an int value for the scale. Even if you try to scale to 1.9 the cast from double to int will bring it down to 1.
I've made a little example:
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.layout.FlowPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
public class JavaFXApplication1 extends Application {
#Override
public void start(Stage primaryStage) {
Canvas canvas = new Canvas(100, 100);
Canvas canvas2 = new Canvas(100, 100);
FlowPane root = new FlowPane();
root.getChildren().addAll(canvas, canvas2);
Scene scene = new Scene(root, 300, 250);
primaryStage.setTitle("Hello World!");
primaryStage.setScene(scene);
primaryStage.show();
redrawImage(canvas, 0.5);
redrawImage(canvas2, 1);
}
private void redrawImage(Canvas canvas, double scale) {
GraphicsContext gc = canvas.getGraphicsContext2D();
gc.clearRect(0, 0, canvas.getWidth(), canvas.getHeight());
gc.scale(scale, scale);
gc.setStroke(Color.RED);
gc.setLineWidth(2);
gc.strokeRect(0, 0, canvas.getWidth(), canvas.getHeight());
gc.setStroke(Color.GREEN);
gc.strokeLine(0, 0, canvas.getWidth(), canvas.getHeight());
gc.strokeLine(0, canvas.getHeight(), canvas.getWidth(), 0);
gc.setStroke(Color.BLUE);
gc.strokeText("TEXT", 50, 50);
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
launch(args);
}
}
With the following result: